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Essential oils and isolated essential oil compounds are known to exert various pharmacological effects, such as antibacterial, antifungal, antiviral, anti-inflammatory, anti-immunomodulatory, antioxidant, and wound healing effects. Based on selected articles, this review deals with the potential antiviral and virucidal activities of essential oils and essential oil compounds together with their mechanism of action as well as in silico studies involving viral and host cell-specific target molecules that are indispensable for virus cell adsorption, penetration, and replication. The reported in vitro and in vivo studies highlight the baseline data about the latest findings of essential oils and essential oil compounds antiviral and virucidal effects on enveloped and non-enveloped viruses, taking into account available biochemical and molecular biological tests. The results of many in vitro studies revealed that several essential oils and essential oil compounds from different medicinal and aromatic plants are potent antiviral and virucidal agents that inhibit viral progeny by blocking different steps of the viral infection/replication cycle of DNA and RNA viruses in various host cell lines. Studies in mice infected with viruses causing respiratory diseases showed that different essential oils and essential oil compounds were able to prolong the life of infected animals, reduce virus titers in brain and lung tissues, and significantly inhibit the synthesis of proinflammatory cytokines and chemokines. In addition, some in vitro studies on hydrophilic nano-delivery systems encapsulating essential oils/essential oil compounds exhibited a promising way to improve the chemical stability and enhance the water solubility, bioavailabilty, and antiviral efficacy of essential oils and essential oil compounds.

Pathogenic biofilm-associated bacteria that adhere to biological or nonbiological surfaces are a big challenge to the healthcare and food industries. Antibiotics or disinfectants often fail in an attempt to eliminate biofilms from those surfaces. Based on selected experimental research, this review deals with the potential biofilm-inhibiting, virulence factor-reducing, and biofilm-eradicating activities of essential oils and single essential oil compounds using Staphylococcus aureus, Escherichia coli, Pseudomonas aeruginosa, and Chromobacterium violaceum as model organisms. In addition, for the bacteria reviewed in this overview, different essential oils and essential oil compounds were reported to be able to modulate the expression of genes that are involved in the formation of autoinducer molecules, biofilms, and virulence factors. The anti-quorum sensing activity of some essential oils and single essential oil compounds was demonstrated using the gram-negative bacterium C. violaceum. Reporter strains of this bacterium produce the violet-colored compound violacein whose synthesis is regulated by quorum sensing autoinducer molecules called acylhomeserinlactones. Of great interest was the discovery that enantiomeric monoterpenes affected the quorum sensing regulation system in different ways. While the (+)-enantiomers of carvone, limonene, and borneol increased violacein formation, their (−)-analogues inhibited violacein production.For the successful eradication of biofilms and the bacteria living inside them, it is absolutely necessary that the lipophilic volatile substances can penetrate into the aqueous channels of biofilms. As shown in recent work, hydrophilic nano-delivery systems encapsulating essential oils/essential oil compounds with antibacterial effects may contribute to overcome this problem.

Background: Propolis consists of a complex mixture of resinous substances collected by honeybees from different plant sources. The objective of this study was to investigate the chemical composition, biological activities, and synergistic properties with antibiotics of propolis samples collected from various geographic origins (Germany, Ireland, and Czech Republic). Methods: The chemical composition of the propolis was analyzed by Gas Liquid Chromatography-Mass Spectrometry (GLC-MS) and High-performance liquid chromatography (HPLC). The minimal inhibitory concentration (MIC) and minimal bactericidal concentration (MBC) were evaluated by the standard broth microdilution method, while synergistic interactions were assessed by checkerboard dilution and time-kill curve assays. Results: HPLC and GLC-MS analyses revealed that ethanol extract of propolis (EEP) and water extracts of propolis (WEP) contained more than 100 different phytochemicals. The most abundant compounds were aromatic alcohols, aromatic acids, cinnamic acid and its esters, fatty acids, and flavanone (chrysin). Czech propolis showed the highest phenolic content (129.83 ± 5.9 mg CAE/g) followed by Irish propolis and German propolis. Furthermore, Irish propolis exhibited the highest value of total flavonoid content (2.86 ± 0.2 mg QE/g) and antioxidant activity (IC50 = 26.45 µg/mL). All propolis samples showed moderate antibacterial effect against Gram-positive microorganisms with MIC ranging from 0.08 mg/mL to 2.5 mg/mL. Moreover, EEP exhibited moderate activity against Gram-negative bacteria with MIC between 0.6 mg/mL to 5 mg/mL. In addition, EEP displayed moderate antifungal activity (MIC values between 0.6–2.5 mg/mL). The results obtained from time kill-kinetic assay and checkerboard dilution test of two-drug combinations between EEP and antibiotics such as vancomycin, oxacillin, and levofloxacin indicate mainly synergistic interactions against drug-resistant microbial pathogens including MRSA and VRE. Conclusions: The propolis extract synergistically enhanced the efficacy of antibiotics, especially those acting on cell wall synthesis (vancomycin and oxacillin) against drug-resistant microorganisms.

The goal of this study was to investigate the antimicrobial activity of bee venom and its main component, melittin, alone or in two-drug and three-drug combinations with antibiotics (vancomycin, oxacillin, and amikacin) or antimicrobial plant secondary metabolites (carvacrol, benzyl isothiocyanate, the alkaloids sanguinarine and berberine) against drug-sensitive and antibiotic-resistant microbial pathogens. The secondary metabolites were selected corresponding to the molecular targets to which they are directed, being different from those of melittin and the antibiotics. The minimal inhibitory concentration (MIC) and minimal bactericidal concentration (MBC) were evaluated by the standard broth microdilution method, while synergistic or additive interactions were assessed by checkerboard dilution and time-kill curve assays. Bee venom and melittin exhibited a broad spectrum of antibacterial activity against 51 strains of both Gram-positive and Gram-negative bacteria with strong anti-MRSA and anti-VRE activity (MIC values between 6 and 800 µg/ml). Moreover, bee venom and melittin showed significant antifungal activity (MIC values between 30 and 100 µg/ml). Carvacrol displayed bactericidal activity, while BITC exhibited bacteriostatic activity against all MRSA and VRE strains tested (reference strains and clinical isolates), both compounds showed a remarkable fungicidal activity with minimum fungicidal concentration (MFC) values between 30 and 200 µg/ml. The DNA intercalating alkaloid sanguinarine showed bactericidal activity against MRSA NCTC 10442 (MBC 20 µg/ml), while berberine exhibited bacteriostatic activity against MRSA NCTC 10442 (MIC 40 µg/ml). Checkerboard dilution tests mostly revealed synergism of two-drug combinations against all the tested microorganisms with FIC indexes between 0.24 and 0.50, except for rapidly growing mycobacteria in which combinations exerted an additive effect (FICI = 0.75–1). In time-kill assays all three-drug combinations exhibited a powerful bactericidal synergistic effect against MRSA NCTC 10442, VRE ATCC 51299, and E. coli ATCC 25922 with a reduction of more than 3log10 in the colony count after 24 h. Our findings suggest that bee venom and melittin synergistically enhanced the bactericidal effect of several antimicrobial agents when applied in combination especially when the drugs affect several and differing molecular targets. These results could lead to the development of novel or complementary antibacterial drugs against MDR pathogens.

Combinations of two or more drugs, which affect different targets, have frequently been used as a new approach against resistant bacteria. In our work we studied the antimicrobial activity (MIC, MBC) of individual drugs (the phenolic monoterpene thymol, EDTA and vancomycin), of two-drug interactions between thymol and EDTA in comparison with three-drug interactions with vancomycin against sensitive and resistant bacteria. Thymol demonstrated moderate bactericidal activity (MBC between 60 and 4000μg/ml) while EDTA only exhibited bacteriostatic activity over a range of 60-4000μg/ml. MICs of vancomycin were between 0.125 and 16μg/ml against Gram-positive and between 32 and 128μg/ml against Gram-negative bacteria. Checkerboard dilution and time-kill curve assays were performed to evaluate the mode of interaction of several combinations against Methicillin-resistant Staphylococcus aureus (MRSA NCTC 10442) and Escherichia coli (ATCC 25922). Checkerboard data indicate indifferent interaction against Gram-positive (FICI=1-1.3) and synergy against Gram-negative bacteria (FICI≈0.4), while time kill analyses suggest synergistic effect in different combinations against both types of bacteria. It is remarkable that the combinations could enhance the sensitivity of E. coli to vancomycin 16-fold to which it is normally insensitive. We have provided proof for the concept, that combinations of known antibiotics with modern phytotherapeutics can expand the spectrum of useful therapeutics.

Plant extracts and essential oils have been widely studied and used as antimicrobial agents in the last decades. In our study we investigated the antimicrobial activities of Olbas(®) Tropfen (in the following named Olbas), a traditionally used complex essential oil distillate, in comparison to its individual essential oil ingredients. Olbas (10 g) consists of three major components such as peppermint oil (5.3 g), eucalyptus oil (2.1 g), and cajuput oil (2.1 g) and of two minor constituents like juniper berry oil (0.3 g) and wintergreen oil (0.2 g). The composition of Olbas and the five individual essential oils were characterized by GLC-MS. According to GLC-MS analysis 1,8-cineol is the main component of the complex essential oil distillate followed by menthol and menthone. The minimum inhibitory and minimum microbicidal concentrations of Olbas and each of the single essential oils were evaluated in 17 species/strains of bacteria and fungi. Time-kill assay was performed to compare the microbicidal activity of Olbas and peppermint oil during several time intervals. Olbas displayed a high antimicrobial activity against all test strains used in this study, among them antibiotic resistant MRSA (methicillin-resistant Staphylococcus aureus) and VRE (vancomycin-resistant Enterococcus). Its antimicrobial activity was comparable to that of peppermint oil which was the most potent one of all individual essential oils tested. In the time kill assay Olbas as well as peppermint oil demonstrated similar microbicidal activities. Based on its wide antimicrobial properties Olbas can be a useful agent for the treatment of uncomplicated infections of skin and respiratory tract.

Background: Extracts and essential oils of medicinal plants are increasingly of interest as novel drugs for antiherpetic agents, since the herpes simplex virus (HSV) might develop resistance to commonly used antiviral drugs. Methods: An aqueous extract of Melissa officinalis as well as phenolic extract compounds, i.e. caffeic acid, p-coumaric acid and rosmarinic acid were examined for their antiviral activity against herpes simplex virus type 1 (HSV-1) in vitro. Results: When drugs were added to HSV-1-infected cells, no antiviral effect was observed as determined by plaque reduction assay and analysis of expression of viral protein ICP0. However, the Melissa extract demonstrated a high virucidal activity against HSV-1, even at very low concentrations of 1.5 µg/ml, whereas similar results for phenolic compounds were only achieved at 100 times higher concentrations. Besides the virucidal activity, the Melissa extract and rosmarinic acid inhibited HSV-1 attachment to host cells in a dose-dependent manner. These results indicate that rosmarinic acid was the main contributor to the antiviral activity of Melissa extract. However, the selectivity index of Melissa extract of 875 against HSV is superior to the selectivity indices of single constituents. Conclusion: Melissa extract exhibits low toxicity, is virucidal and affects HSV-1 attachment to host cells in vitro.

Essential oil of star anise as well as phenylpropanoids and sesquiterpenes, for example, trans-anethole, eugenol,β-eudesmol, farnesol,β-caryophyllene andβ-caryophyllene oxide, which are present in many essential oils, were examined for their antiviral activity against herpes simplex virus type 1 (HSV-1)in vitro. Antiviral activity was analyzed by plaque reduction assays and mode of antiviral action was determined by addition of the drugs to uninfected cells, to the virus prior to infection or to herpesvirus-infected cells. Star anise oil reduced viral infectivity by >99%, phenylpropanoids inhibited HSV infectivity by about 60–80% and sesquiterpenes suppressed herpes virus infection by 40–98%. Both, star anise essential oil and all isolated compounds exhibited anti-HSV-1 activity by direct inactivation of free virus particles in viral suspension assays. All tested drugs interacted in a dose-dependent manner with herpesvirus particles, thereby inactivating viral infectivity. Star anise oil, rich in trans-anethole, revealed a high selectivity index of 160 against HSV, whereas among the isolated compounds onlyβ-caryophyllene displayed a high selectivity index of 140. The presence ofβ-caryophyllene in many essential oils might contribute strongly to their antiviral ability. These results indicate that phenylpropanoids and sesquiterpenes present in essential oils contribute to their antiviral activity against HSV.

Essential oils are complex natural mixtures, their main constituents, e.g. terpenes and phenylpropanoids, being responsible for their biological properties. Essential oils from eucalyptus, tea tree and thyme and their major monoterpene compounds alpha-terpinene, gamma-terpinene, alpha-pinene, p-cymene, terpinen-4-ol, alpha-terpineol, thymol, citral and 1,8-cineole were examined for their antiviral activity against herpes simplex virus type 1 (HSV-1) in vitro. These essential oils were able to reduce viral infectivity by >96%, the monoterpenes inhibited HSV by about >80%. The mode of antiviral action has been determined, only moderate antiviral effects were revealed by essential oils and monoterpenes when these drugs were added to host cells prior to infection or after entry of HSV into cells. However, both essential oils and monoterpenes exhibited high anti-HSV-1 activity by direct inactivation of free virus particles. All tested drugs interacted in a dose-dependent manner with herpesvirus particles thereby inactivating viral infection. Among the analysed compounds, monoterpene hydrocarbons were slightly superior to monoterpene alcohols in their antiviral activity, alpha-pinene and alpha-terpineol revealed the highest selectivity index. However, mixtures of different monoterpenes present in natural tea tree essential oil revealed a ten-fold higher selectivity index and a lower toxicity than its isolated single monoterpenes.

Herbal remedies are multicomponent mixtures by their nature as well as by pharmaceutical definition. Being a multicomponent mixture is not only a crucial property of herbal remedies, it also represents a precondition for interactions such as synergism or antagonism. Until now, only a few phytomedicines are accurately described concerning the interactions of their active components. The aim of this study was to search for interactions within such a naturally given multi-component mixture and to discuss the pharmaceutical and clinical impacts. The thyme oil chosen for the examination belongs to the essential oils with the most pronounced antimicrobial activity. Antibiotic activity of thyme oil and single active components were tested against six different strains of microorganisms. The checkerboard assay was used to search for interactions. The time-kill assay was used to verify the observed effects and to get information about the temporal resolution of the antimicrobial activity. The degree of the detected interactions corresponded with the demarcating FICI measure of 0.5, which separates the additive from the over-additive (synergistic) effects. Therefore, the observed effect was called a "borderline case of synergism" or, respectively, "partial synergism". Partial synergism was observed only in the presence of Klebsiella pneumoniae. Additive antimicrobial activity was observed for the combination of the two monosubstances carvacrol plus linalool and thymol plus linalool as well as with the combination of the two essential oils of the carvacrol and linalool chemotypes. An increase of the carvacrol oil concentration from one to two times the MIC resulted in a considerable acceleration of the kill-rate. Thyme oil is composed of several different components that show antimicrobial activity (at least: carvacrol, thymol and linalool). The antimicrobial activity of thyme oil is partly based on additive effects, which might especially enhance the rapidity of the antimicrobial action. In addition, a mixture of several active ingredients that varies in its composition from year to year and from lot to lot as is the case with herbal remedies may be more stable concerning the antimicrobial activity than mixtures containing just a single active component.

The effect of anise oil, dwarf-pine oil and chamomile oil against different thymidine-kinase-positive (aciclovir-sensitive) and thymidine-kinase-negative (aciclovir-resistant) herpes simplex virus type 1 (HSV-1) strains was examined. Clinical HSV-1 isolates containing frameshift mutations in the thymidine kinase (TK) gene, an insertion or a deletion, yield a non-functional thymidine kinase enzyme resulting in phenotypical resistance against aciclovir. The inhibitory activity of three different essential oils against herpes simplex virus isolates was tested in-vitro using a plaque reduction assay. All essential oils exhibited high levels of antiviral activity against aciclovir-sensitive HSV strain KOS and aciclovir-resistant clinical HSV isolates as well as aciclovir-resistant strain Angelotti. At maximum noncytotoxic concentrations of the plant oils, plaque formation was significantly reduced by 96.6–99.9%, when herpesviruses were preincubated with drugs before attachment to host cells. No significant effect on viral infectivity could be achieved by adding these compounds during the replication phase. These results indicate that anise oil, dwarf-pine oil and chamomile oil affected the virus by interrupting adsorption of herpesviruses and in a different manner than aciclovir, which is effective after attachment inside the infected cells. Thus the investigated essential oils are capable of exerting a direct effect on HSV and might be useful in the treatment of drug-resistant viruses. Chamomile oil did not reveal any irritating potential on hen's egg chorioallantoic membrane, demonstrated the highest selectivity index among the oils tested and was highly active against clinically relevant aciclovir-resistant HSV-1 strains.

Essential oils from anise, hyssop, thyme, ginger, camomile and sandalwood were screened for their inhibitory effect against herpes simplex virus type 2 (HSV-2) in vitro on RC-37 cells using a plaque reduction assay. Genital herpes is a chronic, persistent infection spreading efficiently and silently as sexually transmitted disease through the population. Antiviral agents currently applied for the treatment of herpesvirus infections include acyclovir and its derivatives. The inhibitory concentrations (IC50) were determined at 0.016%, 0.0075%, 0.007%, 0.004%, 0.003% and 0.0015% for anise oil, hyssop oil, thyme oil, ginger oil, camomile oil and sandalwood oil, respectively. A clearly dose-dependent virucidal activity against HSV-2 could be demonstrated for all essential oils tested. In order to determine the mode of the inhibitory effect, essential oils were added at different stages during the viral infection cycle. At maximum noncytotoxic concentrations of the essential oils, plaque formation was significantly reduced by more than 90% when HSV-2 was preincubated with hyssop oil, thyme oil or ginger oil. However, no inhibitory effect could be observed when the essential oils were added to the cells prior to infection with HSV-2 or after the adsorption period. These results indicate that essential oils affected HSV-2 mainly before adsorption probably by interacting with the viral envelope. Camomile oil exhibited a high selectivity index and seems to be a promising candidate for topical therapeutic application as virucidal agents for treatment of herpes genitalis.

Brackenridgea zanguebarica is a small tree that is used in traditional African medicine as a type of cure-all for many diseases, including the treatment of wounds. The yellow bark of B. zanguebarica was used for the preparation of an ethanolic extract, which was tested in various concentrations against eleven bacteria, Herpes simplex virus type 1 (HSV-1) and different human tumour cell lines. The extract that contains different polyphenolic substances like calodenin B. Cell growth inhibition, assessed via MTT-assay, was found in all tested human cell lines with IC50 values (concentration of extract that reduced cell viability by 50%) between 33 μg dry extract/mL for HL-60 human myeloid leukaemia cells and 93 μg dry extract/mL for HaCaT human keratinocytes. Staining with Annexin-V-FLUOS and JC-1 followed by subsequent analysis via flow cytometry revealed significant apoptosis-inducing properties. Analysis of caspase activity using a fluorogenic caspase-3 substrate showed a significant caspase activity in Jurkat T-cells after incubation with the extract. The bark extract had a pronounced activity against free HSV-1 and a strong antibacterial activity against Gram-positive strains (MICs: 6–24 μg dry extract/mL), which are often involved in skin infections. Additionally, no irritating properties of the extract could be observed in hen-egg test chorioallantoic membrane (HET-CAM) assay. These findings give a rationale for the traditional use of B. zanguebarica and are a basis for further analysis of the plant's components, their biological activity, and its use in modern phytotherapy.

In this open clinical trial conducted in 10 veterinary practices, Ginkgo leaf extract was administered as a dietary supplement to 42 elderly dogs (mean age 11.4 years) at a daily dose of 40 mg/ 10 kg body weight for 8 weeks. The "severity of the geriatric condition" in dogs with a history of geriatric behavioural disturbances (mean duration 12 months), was significantly reduced after 8 weeks of treatment (P = 0.0002). The positive effect was already apparent after 4 weeks. Thirty-six % of the dogs were completely free of clinical signs at study end. Overall efficacy of treatment as judged by the investigator was good or very good in 79% of the dogs. Five of six clinical sign scores (disorientation, sleep/activity changes, behavioural changes, general behaviour and general physical condition/vitality) also showed a significant decrease over the treatment period. In conclusion, these findings provide promising results that could increase the quality of life in the elderly dog and, as a consequence, that of the pet owner. The Ginkgo leaf extract appears to be an efficacious agent that provides a safe dietary supplement for the elderly dog with age-related behavioural disturbances.

Hintergrund: Australisches TeebaumOl ist ein leicht gelbliches Atherisches Ol, das hauptsAchlich aus den BlAttern von Melaleuca alternifolia durch Wasserdampfdestillation gewonnen wird. In den letzten Jahren wurde es verstArkt in der Kosmetik, in der Krankenpflege und in der Selbstmedikation aufgrund seiner antimikrobiellen, antiseptischen und antientzUndlichen Wirkung angewendet. Zielsetzung: Charakterisierung von Melaleuca alternifolia betreffend Botanik, Inhaltsstoffe, QualitAt sowie Wirksamkeit und VertrAglichkeit. Methoden: Systematische Analyse und Bewertung von pharmakologischen und toxikologischen sowie In-vitro- und In-vivo-Studien. Ergebnisse und Schlussfolgerungen: In-vitro-Untersuchungen haben gezeigt, dass TeebaumOl Uber eine ausgezeichnete antimikrobielle Wirkung mit breitem Wirkungsspektrum gegen Gram-positive und Gram-negative Bakterien sowie gegen Pilze verfUgt. Gute Ergebnisse wurden auch bei der Behandlung von Acne vulgaris, Tinea pedis und Onychomykosen erzielt. Andererseits ist bekannt, dass Australisches TeebaumOl auch unerwUnschte Nebenwirkungen, wie z.B. Hautirritationen und Allergien, verursachen kann. Man nimmt an, dass oxidierte Monoterpene die eigentlichen Allergene des Ols darstellen.

Localised dermatitis, for example unspecific eczema or skinfold pyoderma, is a very common diagnosis in dogs. Typical and impressive complaints are pruritus, erythema, erosion and oozing surface. With respect to the underlying disease dermatological treatment is indicated, usually based on antimicrobial and antipruriginous active substances, it can include transient glucocorticoids. An effective and safe alternative might be a phytotherapeutic topical preparation containing tea tree oil. Tea tree oil exerts both antimicrobial and antipruriginous effects. In an open multicenter study efficacy and safety of a standardized 10% tea tree oil cream applied thinly and twice daily for 4 weeks was tested in 53 dogs with chronic dermatitis, particularly non-specific eczema, allergic dermatitis, interdigital pyoderma, acral lick dermatitis and skinfold pyoderma. Analysis of efficacy assessed by investigating veterinarians showed a good or very good response to treatment for 82% of the dogs, significant at a 5% level (p = 0.05). At the end of the study a strong and significant reduction (p = 0.001) as well as disappearance of major symptoms were observed. Only two adverse events (local reactions) possibly related to tea tree oil occurred during therapy. Consequently the tested study medication (Bogaskin) can be considered an alternative for uncomplicated and localised dermatitis in dogs. Bogaskin might allow reduction of other pharmaceutical products, perhaps even replace standard therapy.

PADMA 28 is a multicompound preparation of 20 herbs, calcium sulphate, and camphor, derived from Tibetan medicine. It is usually used in the treatment of peripheral circulatory disorders, accompanied by the symptoms tingling, formication, heaviness and tenseness in arms and legs, numbness in hands and feet, and cramps in the calf. Recently, the question of whether appropriate preparations of PADMA 28 also exhibit antibacterial and antimycotic activity has often been raised. As there are as yet no experimental findings that answer this question, an in vitro study was carried out. In a parallel survey we investigated the antimicrobial properties of 5 herbal drugs which are commonly used in the traditional European folk medicine for the topical treatment of mild skin infections, wounds and eczematous skin lesions.The minimum inhibitory concentrations (MIC) and the minimum bactericidal concentrations (MBC) of alcohol-based (tinctures) and aqueous (teas) herbal drug preparations were determined in vitro by a broth microdilution method for 5 Gram-positive and 5 Gram-negative bacteria, as well as the yeast Candida albicans.The aqueous and alcohol-based PADMA 28 preparations as well as the corresponding preparations of the European herbal drugs showed an antibacterial effect against Gram-positive bacteria in vitro. These bacteria revealed a somewhat higher sensitivity to the teas prepared from the European herbal drugs (MIC: 1.3-20.0 mg/ml) than to the aqueous preparations of PADMA 28 (MIC: 5.0-40.0 mg/ml). The better antibacterial activity of the European herbal drugs is probably based on their relatively high amount of tanning agents. On the other hand, all tested plant preparations inhibited not at all or only insufficiently the growth of the Gram-negative bacteria tested and that of Candida albicans. The ethanolic PADMA 28 tinctures showed an improved inhibitory effect on the Gram-positive bacteria (MIC: 0.38-1.51% tincture or 0.38-1.51 mg PADMA 28/ml) compared with the aqueous preparations; this effect is comparable to the ethanolic tinctures of the tested European herbal drugs (MIC: 0.4-1.6/3.2% tincture or 0.4-1.6/3.2 mg herbal drug/ml).All tested tea preparations and alcoholic tinctures of PADMA 28 as well as those of the selected European herbal drugs exhibited evident antibacterial effects against Gram-positive bacteria in vitro. On the other hand, except for Klebsiella pneumoniae, all Gram-negative bacteria tested and the yeast Candida albicans were insensitive against the different aqueous and alcohol-based plant extracts.

Objectives Drug combinations consisting of the DNA intercalating benzophenanthridine alkaloid sanguinarine, the chelator EDTA with the antibiotic streptomycin were tested against several Gram-positive and Gram-negative bacteria, including multi-resistant clinical isolates. Methods Microdilution, checkerboard and time kill curve methods were used to investigate the antibacterial activity of the individual drugs and the potential synergistic activity of combinations. Key findings Sanguinarine demonstrated a strong activity against Gram-positive and Gram-negative bacteria (minimum inhibitory concentrations, MIC = 0.5–128 μg/ml), while streptomycin was active against Gram-negative strains (MIC = 2–128 μg/ml). EDTA showed only bacteriostatic activity. Indifference to synergistic activity was seen in the two-drug combinations sanguinarine + EDTA and sanguinarine + streptomycin (fractional inhibitory concentration index = 0.1–1.5), while the three-drug combination of sanguinarine + EDTA + streptomycin showed synergistic activity against almost all the strains (except methicillin-resistant Staphylococcus aureus), as well as a strong reduction in the effective doses (dose reduction index = 2–16 times) of sanguinarine, EDTA and streptomycin. In time kill studies, a substantial synergistic interaction of the three-drug combination was detected against Escherichia coli and Klebsiella pneumoniae. Conclusions The combination of drugs, which interfere with different molecular targets, can be an important strategy to combat multidrug resistant bacteria.

Antiviral agents frequently applied for treatment of herpesvirus infections include acyclovir and its derivatives. The antiviral effect of a triterpene extract of birch bark and its major pentacyclic triterpenes, i.e. betulin, lupeol and betulinic acid against acyclovir-sensitive and acyclovir-resistant HSV type 1 strains was examined. The cytotoxic effect of a phytochemically defined birch bark triterpene extract (TE) as well as different pentacyclic triterpenes was analyzed in cell culture, and revealed a moderate cytotoxicity on RC-37 cells. TE, betulin, lupeol and betulinic acid exhibited high levels of antiviral activity against HSV-1 in viral suspension tests with IC50 values ranging between 0.2 and 0.5 μg/ml. Infectivity of acyclovir-sensitive and clinical isolates of acyclovir-resistant HSV-1 strains was significantly reduced by all tested compounds and a direct concentration- and time-dependent antiherpetic activity could be demonstrated. In order to determine the mode of antiviral action, TE and the compounds were added at different times during the viral infection cycle. Addition of these drugs to uninfected cells prior to infection or to herpesvirus-infected cells during intracellular replication had low effect on virus multiplication. Minor virucidal activity of triterpenes was observed, however both TE and tested compounds exhibited high anti-herpetic activity when viruses were pretreated with these drugs prior to infection. Pentacyclic triterpenes inhibit acyclovir-sensitive and acyclovir-resistant clinical isolates of HSV-1 in the early phase of infection.

Summary The essential tea tree oil has been widely used in modern medicine and cosmetics in recent years. Although there are clinical data to show the benefical effects (e.g. antiseptic, antimicrobial, antioxidative) of this oil, dose-response studies are lacking. This paper reviews the clinical use of this essential oil, especially as a topical application.

Eucalyptus globulus Labill (Myrtaceae) is the principal source of eucalyptus oil in the world and has been used as an antiseptic and for relieving symptoms of cough, cold, sore throat, and other infections. The oil, well known as 'eucalyptus oil' commercially, has been produced from the leaves. Biological properties of the essential oil of fruits from E. globulus have not been investigated much.The present study was performed to examine the antimicrobial activity of the fruit oil of E. globulus (EGF) and the leaf oils of E. globulus (EGL), E. radiata Sieber ex DC (ERL) and E. citriodora Hook (ECL) against multidrug-resistant (MDR) bacteria. Furthermore, this study was attempted to characterize the oils as well as to establish a relationship between the chemical composition and the corresponding antimicrobial properties.The chemical composition of the oils was analyzed by GLC-MS. The oils and isolated major components of the oils were tested against MDR bacteria using the broth microdilution method.EGF exerted the most pronounced activity against methicillin-resistant Staphylococcus aureus (MIC ~ 250 µg/ml). EGF mainly consisted of aromadendrene (31.17%), whereas ECL had citronellal (90.07%) and citronellol (4.32%) as the major compounds. 1,8-cineole was most abundant in EGL (86.51%) and ERL (82.66%).The activity of the oils can be ranked as EGFECLERL ~ EGL. However, all the oils and the components were hardly active against MDR Gram-negative bacteria. Aromadendrene was found to be the most active, followed by citronellol, citronellal and 1,8-cineole.

Objectives The aim was to determine the chemical composition of the essential oil of Kadsura longipedunculata and the biological activity of the oil and its major components. Methods The essential oil from stem bark of Kadsura longipedunculata was analysed by capillary gas chromatography (GLC/FID) and gas chromatography–mass spectrometry (GLC/MS). The ability of the oil to reduce diphenylpicrylhydrazine (DPPH•) was used to evaluate the antioxidant activity. Inhibition of both lipoxygenase and prostaglandin E2 was used to assess the anti-inflammatory activity. Antimicrobial activity was studied in vitro against a range of bacteria and fungi using diffusion and microdilution methods. Inhibition of trypanosome proliferation was assessed using resazurin as vital stain. The in-vitro cytotoxicity of the essential oil on six human cancer cell lines (HepG2, MIA PaCa-2, HeLa, HL-60, MDA-MB-231 and SW-480) was examined using the MTT assay. Key findings Fifty compounds, representing 97.63% of total oil, were identified. δ-Cadinene (21.79%), camphene (7.27%), borneol (6.05%), cubenol (5.12%) and δ-cadinol (5.11%) were found to be the major components of the oil. The oil exerted a good antimicrobial activity against all Gram-positive bacteria tested, including methicillin-resistant Staphylococcus aureus and vancomycin-resistant Enterococcus faecalis. Streptococcus pyogenes and S. agalactiae were the most sensitive bacteria with a minimal inhibitory concentration (MIC) of 60 µg/ml oil. The essential oil showed a moderate fungicidal activity against yeasts, but it did not show any activity against Gram-negative bacteria. The essential oil showed a good trypanocidal activity in Trypanosoma b. brucei with an IC50 value of 50.52 ± 0.029 µg/ml. Radical scavenging activity had an IC50 value of 3.06 ± 0.79 mg/ml. 5-Lipoxygenase inhibition (IC50 = 38.58 µg/ml) and prostaglandin E2 production inhibition (28.82% at 25 µg/ml) accounted for anti-inflammatory activity of the oil. The oil exhibited some degree of cytotoxic activity against MIA PaCa-2, HepG-2 and SW-480 cell lines with IC50 values of 133.53, 136.96 and 136.62 µg/ml, respectively. The oil increased caspase 3/7 activity (an indicator of apoptosis) 2.5–4 fold in MIA Paca-2 cells. Camphene and borneol did not show antioxidant activity. However, both compounds exhibited some degree of antimicrobial, trypanocidal, anti-inflammatory and cytotoxic activity. Conclusions This investigation provided evidence for, and confirmed the efficacy of, K. longipedunculata, a traditionally used Chinese medicinal plant for the treatment of inflammation and infection.

The aim of the present study was to investigate the chemical composition of the essential oil of the fruits of Eucalyptus globulus and to examine the potential application of the fruit oil against multidrug-resistant bacteria. GLC/MS analysis in the fruit oil showed that aromadendrene was the main compound followed by 1,8-cineole and globulol. The three most abundant components of the fruit oil were also tested individually against microorganisms. In addition, the synergistic effects of combinations of the major constituents (aromadendrene and 1,8-cineole) of the fruit oil were also investigated. All Gram-positive bacteria were susceptible to the fruit oil with different degrees of susceptibility as determined by microdilution method. The oil exerted a marked inhibition against multidrug-resistant bacteria such as methicillin-resistant Staphylococcus aureus (MRSA) and vancomycin-resistant enterococci (VRE) Enterococcus faecalis. The results indicated that aromadendrene might be responsible for the antimicrobial properties, whereas 1,8-cineole and globulol exhibited low activities. The checkerboard assay demonstrated that combinations of 1,8-cineole and aromadendrene reduce the MIC in most cases in an additive way, whereas the time-kill assay indicates a synergistic effect.

Essential oils are complex natural mixtures, their main constituents, e.g. terpenes and phenylpropanoids, being responsible for their biological properties. Essential oils from eucalyptus, tea tree and thyme and their major monoterpene compounds α‐terpinene, γ‐terpinene, α‐pinene, p‐cymene, terpinen‐4‐ol, α‐terpineol, thymol, citral and 1,8‐cineole were examined for their antiviral activity against herpes simplex virus type 1 (HSV‐1) in vitro. These essential oils were able to reduce viral infectivity by >96%, the monoterpenes inhibited HSV by about >80%. The mode of antiviral action has been determined, only moderate antiviral effects were revealed by essential oils and monoterpenes when these drugs were added to host cells prior to infection or after entry of HSV into cells. However, both essential oils and monoterpenes exhibited high anti‐HSV‐1 activity by direct inactivation of free virus particles. All tested drugs interacted in a dose‐dependent manner with herpesvirus particles thereby inactivating viral infection. Among the analysed compounds, monoterpene hydrocarbons were slightly superior to monoterpene alcohols in their antiviral activity, α‐pinene and α‐terpineol revealed the highest selectivity index. However, mixtures of different monoterpenes present in natural tea tree essential oil revealed a ten‐fold higher selectivity index and a lower toxicity than its isolated single monoterpenes. Copyright © 2009 John Wiley & Sons, Ltd.

The abundant use of anti-infective agents resulted in the emergence of drug-resistant bacteria, fungi, and viruses. To overcome the increasing resistance of pathogenic microbes, a variety of medicinal plants have been screened worldwide for their antimicrobial properties. The aim is to find new, effective antimicrobial agents with novel modes of actions. Essential oils derived from aromatic medicinal plants have been reported to exhibit exceptionally good antimicrobial effects against bacteria, yeasts, filamentous fungi, and viruses. The progress of this expanding scientific field will be documented by the most important results published in the last decade.

Genital herpes caused by herpes simplex virus type 2 (HSV-2) is a chronic, persistent infection spreading efficiently and silently as sexually transmitted disease through the population. Antiviral agents currently applied for the treatment of herpesvirus infections include acyclovir and derivatives. Aqueous and ethanolic extracts of propolis were phytochemically analysed, different polyphenols, flavonoids and phenylcarboxylic acids were identified as major constituents. The aqueous propolis extract revealed a relatively high amount of phenylcarboxylic acids and low concentrations flavonoids when compared to the ethanolic special extract GH 2002. The cytotoxic and antiherpetic effect of propolis extracts against HSV-2 was analysed in cell culture, and revealed a moderate cytotoxicity on RC-37 cells. The 50% inhibitory concentration (IC(50)) of aqueous and ethanolic GH 2002 propolis extracts for HSV-2 plaque formation was determined at 0.0005% and 0.0004%, respectively. Both propolis extracts exhibited high levels of antiviral activity against HSV-2 in viral suspension tests, infectivity was significantly reduced by >99% and a direct concentration- and time-dependent antiherpetic activity could be demonstrated for both extracts. In order to determine the mode of virus suppression by propolis, the extracts were added at different times during the viral infection cycle. Addition of these drugs to uninfected cells prior to infection or to herpesvirus-infected cells during intracellular replication had no effect on virus multiplication. However both propolis extracts exhibited high anti-herpetic activity when viruses were pretreated with these drugs prior to infection. Selectivity indices were determined at 80 and 42.5 for the aqueous and ethanolic extract, respectively, thus propolis extracts might be suitable for topical therapy in recurrent herpetic infection.

Pancreatic cancer is one of the most aggressive human malignancies, with an extremely poor prognosis. The paucity of curative therapies has translated into an overall 5-year survival rate of less than 5%, underscoring a desperate need for new therapeutic options. Artesunate (ART), clinically used as anti-malarial agent, has recently revealed remarkable anti-tumor activity. However, the mechanisms underlying those activities in pancreatic cancer are not yet known. Here we evaluated the anti-tumor activity of Artesunate and the possible underlying mechanisms in pancreatic cancer. MiaPaCa-2 (poorly differentiated) and BxPC-3 (moderately differentiated) pancreatic cancer cell lines were treated with Artesunate and the effect was monitored by a tetrazolium-based assay (MTS) for evaluating cell viability and by flow cytometry and caspase 3/7 activation for apoptosis evaluation. In addition cDNA arrays were used to identify differentially expressed genes. The microarray data were then validated by RT-PCR and Western blotting. Moreover, pathways associated with these expression changes were identified using the Ingenuity Pathway Analysis. The expression analysis identified a common set of genes that were regulated by Artesunate in pancreatic cancer. Our results provide the first in vitro evidence for the therapeutic utility of Artesunate in pancreatic cancer. Moreover, we identified Artesunate as a novel topoisomerase IIalpha inhibitor that inhibits pancreatic cancer growth through modulation of multiple signaling pathways. The present analysis is a starting point for the generation of hypotheses on candidate genes and for a more detailed dissection of the functional role of individual genes for the activity of Artesunate in tumor cells.

Background Aqueous extracts from leaves of well known species of the Lamiaceae family were examined for their potency to inhibit infection by human immunodeficiency virus type 1 (HIV-1). Results Extracts from lemon balm (Melissa officinalis L.), peppermint (Mentha × piperita L.), and sage (Salvia officinalis L.) exhibited a high and concentration-dependent activity against the infection of HIV-1 in T-cell lines, primary macrophages, and in ex vivo tonsil histocultures with 50% inhibitory concentrations as low as 0.004%. The aqueous Lamiaceae extracts did not or only at very high concentrations interfere with cell viability. Mechanistically, extract exposure of free virions potently and rapidly inhibited infection, while exposure of surface-bound virions or target cells alone had virtually no antiviral effect. In line with this observation, a virion-fusion assay demonstrated that HIV-1 entry was drastically impaired following treatment of particles with Lamiaceae extracts, and the magnitude of this effect at the early stage of infection correlated with the inhibitory potency on HIV-1 replication. Extracts were active against virions carrying diverse envelopes (X4 and R5 HIV-1, vesicular stomatitis virus, ecotropic murine leukemia virus), but not against a non-enveloped adenovirus. Following exposure to Lamiaceae extracts, the stability of virions as well as virion-associated levels of envelope glycoprotein and processed Gag protein were unaffected, while, surprisingly, sucrose-density equilibrium gradient analyses disclosed a marked increase of virion density. Conclusion Aqueous extracts from Lamiaceae can drastically and rapidly reduce the infectivity of HIV-1 virions at non-cytotoxic concentrations. An extract-induced enhancement of the virion's density prior to its surface engagement appears to be the most likely mode of action. By harbouring also a strong activity against herpes simplex virus type 2, these extracts may provide a basis for the development of novel virucidal topical microbicides.

Extracts and essential oils of medicinal plants are increasingly of interest as novel drugs of antimicrobial and antiviral agents, since herpes simplex virus (HSV) might develop resistance to commonly used antiviral agents. Melissa officinalis essential oil was phytochemically examined by GC-MS analysis, its main constituents were identified as monoterpenaldehydes citral a, citral b and citronellal. The antiviral effect of lemon balm oil, the essential oil of Melissa officinalis, on herpes simplex virus was examined. The inhibitory activity against herpes simplex virus type 1 (HSV-1)and herpes simplex virus type 2 (HSV-2) was tested in vitro on monkey kidney cells using a plaque reduction assay. The 50% inhibitory concentration (IC50) of balm oil for herpes simplex virus plaque formation was determined at high dilutions of 0.0004% and 0.00008% for HSV-1 and HSV-2, respectively. At noncytotoxic concentrations of the oil,plaque formation was significantly reduced by 98.8% for HSV-1 and 97.2% for HSV-2, higher concentrations of lemon balm oil abolished viral infectivity nearly completely. In order to determine the mode of antiviral action of this essential oil, time-on-addition assays were performed. Both herpesviruses were significantly inhibited by pretreatment with balm oil prior to infection of cells. These results indicate that Melissa oil affected the virus before adsorption, but not after penetration into the host cell, thus lemon balm oil is capable of exerting a direct antiviral effect on herpesviruses. Considering the lipophilic nature of lemon balm essential oil, which enables it to penetrate the skin, and a high selectivity index, Melissa officinalis oil might be suitable for topical treatment of herpetic infections.

Eine Reihe von pflanzlichen Arzneimitteln lassen sich bei den verschiedenen gastrointestinalen Beschwerden und Symptomen von tumorkranken Menschen (Halitosis, Ubelkeit, Erbrechen, dyspeptische Beschwerden, Reizdarmsymptome, Obstipation, Diarrhoe) sinnvoll einsetzen als palliative und supportive Behandlung. Die Basis fUr die Anwendung bilden einerseits therapeutische Empirie und andererseits wissenschaftlich erhobene Daten und klinische Studien, wobei derzeit nur ein kleinerer Teil mit Tumorpatienten durchgefUhrt wurde. Unter diesen Gesichtspunkten stehen vielfAltige Arzneidrogen, phytotherapeutische Zubereitungen und Kombinationen zur VerfUgung: Atherische Ole (z.B. Pfefferminze, Salbei, australischer Teebaum), Bitterstoff-Drogen (z.B. Wermut, Enzian, Artischocke, Iberis), Teezubereitungen und Tinkturen (z.B. Kamille, Brombeere, Frauenmantel, GAnsefinger, Tormentill, Uzara, Szygium, Heidelbeere, Schwarztee), Laxanzien (z.B. Rhabarber, Faulbaum, Senna, Aloe, Leinsamen, Flohsamen) und Fertigarzneimittel wie z.B. Padmed Laxan und Iberogast. Die vorhandenen Erfahrungen und die bisherigen klinischen Studien lassen die mOglichen Vorteile, die geringe HAufigkeit unerwUnschter Wirkungen, aber auch die EinschrAnkungen der phytotherapeutischen Therapien deutlich hervortreten. Insgesamt scheint es, dass das Potential der symptomorientierten Therapie mit pflanzlichen Arzneimitteln in der Behandlung gastrointestinaler Beschwerden bei Patienten mit Tumorerkrankungen unterschAtzt wird.

Tissue cultures of Pimpinella anisum and P. major were used to study the biosynthesis of pseudoisoeugenols. The putative precursors were labelled with 13C with one exception that was labelled with 14C. The incorporation of the label was controlled by 13CNMR and liquid scintil­ lation, respectively. The biosynthetic sequence found was L-phenylalanine, p-cinnamic acid, p-coumaric acid, p-hydroxycoum aric alcohol, p-methoxycoumaric alcohol and anethol. The incorporation rates ranged from 0.5% to 25%.

Unorganized callus and leaf/root-differentiating callus cultures of Pimpinella major have been established in liquid nutrient medium. Their capacity to accumulate rare phenylpropanoids such as epoxy-pseudoisoeugenol tiglate, epoxy-anol tiglate and anol tiglate was compared with that of seedlings and whole plants. The unorganized callus cultures were not able to accumulate any phenylpropanoids. In comparison, the leaf/root-differentiating callus culture promoted the accumulation of epoxy-pseudoisoeugenol tiglate (up to 90 mg/100 g fr.wt.) but not that of anol-derivatives. The accumulated amount of EPT in PMD-SH was comparable with that in plant seedlings.

Aqueous and ethanolic extracts of Salvia officinalis (Lamiaceae) from two different locations (Garden and Swabian Mountains) were examined in vitro on RC-37 cells for their antiviral activity against herpes simplex virus type 1 (HSV-1) and type 2 (HSV-2) using a plaque reduction assay. The 50% inhibitory concentrations (IC50) of the extracts for HSV plaque formation were determined in dose-response studies. All extracts tested revealed a high virucidal activity against free HSV-1 and HSV-2. The experimental data exhibited a significant higher sensitivity of HSV against the extracts derived from Garden in comparison with those from Swabian Mountains. The most active one was the Garden 20% ethanol extract with IC50 values of 0.18 microg/ml for HSV-1 and 0.04 microg/ml for HSV-2. In order to identify the mode of antiviral action, the extracts were added to the host cells (RC-37) or viruses at different stages of infection. Independently of the location, both types of herpes viruses were considerably inactivated after treatment with the extracts prior to cell infection. Plaque formation was significantly reduced by >90% for HSV-1 and by >99% for HSV-2. Pretreatment of the host cells with both Garden and Swabian Mountains 20% and 40% ethanolic extracts prior to virus infection revealed a strong reduction of HSV-2 plaque formation by 94% and 70% (Garden) and 99% and 45% (Swabian Mountains), respectively. In time-activity studies with free HSV-1 over a period of 2h, a clearly time-dependent activity was demonstrated whereby the ethanolic extracts of both locations revealed a much higher activity than the aqueous ones. The 20% ethanolic extracts of both locations are of special interest and were effective when added to host cells and free virus. A topical application with a dual mode of action would be ideal against recurrent herpes infections.

Acyclovir-resistant clinical isolates of herpes simplex virus type 1 (HSV-1) were analyzed in vitro for their susceptibilities to essential oils of ginger, thyme, hyssop, and sandalwood. All essential oils exhibited high levels of virucidal activity against acyclovir-sensitive strain KOS and acyclovir-resistant HSV-1 clinical isolates and reduced plaque formation significantly.

The virucidal effect of peppermint oil, the essential oil of Mentha piperita, against herpes simplex virus was examined. The inhibitory activity against herpes simplex virus type 1 (HSV-1) and herpes simplex virus type 2 (HSV-2) was tested in vitro on RC-37 cells using a plaque reduction assay. The 50% inhibitory concentration (IC50) of peppermint oil for herpes simplex virus plaque formation was determined at 0.002% and 0.0008% for HSV-1 and HSV-2, respectively. Peppermint oil exhibited high levels of virucidal activity against HSV-1 and HSV-2 in viral suspension tests. At noncytotoxic concentrations of the oil, plaque formation was significantly reduced by 82% and 92% for HSV-1 and HSV-2, respectively. Higher concentrations of peppermint oil reduced viral titers of both herpesviruses by more than 90%. A clearly time-dependent activity could be demonstrated, after 3 h of incubation of herpes simplex virus with peppermint oil an antiviral activity of about 99% could be demonstrated. In order to determine the mode of antiviral action of the essential oil, peppermint oil was added at different times to the cells or viruses during infection. Both herpesviruses were significantly inhibited when herpes simplex virus was pretreated with the essential oil prior to adsorption. These results indicate that peppermint oil affected the virus before adsorption, but not after penetration into the host cell. Thus this essential oil is capable to exert a direct virucidal effect on HSV. Peppermint oil is also active against an acyclovir resistant strain of HSV-1 (HSV-1-ACV(res)), plaque formation was significantly reduced by 99%. Considering the lipophilic nature of the oil which enables it to penetrate the skin, peppermint oil might be suitable for topical therapeutic use as virucidal agent in recurrent herpes infection.

The lipophilic yeast Malassezia pachydermatis is part of the normal skin flora of most warm-blooded organisms. In a number of surveys it could be demonstrated that this yeast species might be involved in different skin diseases like seborrhoeic dermatitis, especially in dogs and cats. In order to look for an alternative therapeutic agent to the commonly used antimycotic and antiseptic synthetic substances the in vitro activity of Australian tea tree oil, the essential oil of Melaleuca alternifolia, against several strains of Malassezia pachydermatis was examined. All tested strains showed remarkably high susceptibility to tea tree oil. With these results the excellent antibacterial activity of tea tree oil is extended to a new group of fungal pathogens colonizing mainly mammals' skin. During the last ten years there was an increasing popularity of tea tree oil containing human health care products. The presented data open up new horizons for this essential oil as a promising alternative agent for topical use in veterinary medicine as well.