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The secular use of plants in popular medicine has emerged as a source for the discovery of new compounds capable of curing infections. Among microbial resistance to commercial drugs, species such as Piper diospyrifolium Kunth, which are used in popular therapy, are targets for pharmacological studies. With this in mind, antimicrobial experiments with the essential oil from the P. diospyrifolium (PDEO) species were performed and its constituents were elucidated. The oil compounds were identified by gas chromatography coupled to mass spectrometry (GC/MS). The broth microdilution method with colorimetric readings for bacterial tests (Escherichia coli and Staphylococcus aureus) and spectrophotometric readings for fungal tests (Candida albicans and Candida tropicalis), whose data were used to create a cell viability curve and calculate its IC50 against fungal cells, were used to determine the minimum inhibitory concentration of the oil and its combined action with commercial drugs. The oil's minimal fungicidal concentration and its action over fungal morphological transition were analyzed by subculture and microculture, respectively. Chemical analysis revealed Z-Carpacin, Pogostol and E-Caryophyllene as the most abundant compounds. Results from the intrinsic analysis were considered clinically irrelevant, however the oil presented a synergistic effect against multiresistant E. coli and S. aureus strains when associated with gentamicin, and against the standard and isolated C. tropicalis strains with fluconazole. A fungicidal effect was observed against the C. albicans isolate. Candida spp. hyphae inhibition was verified for all strains at the highest tested concentrations. The P. diospyrifolium essential oil presented a promising effect when associated with commercial drugs and against a fungal virulence factor. Thus, the oil presented active compounds which may help the development of new drugs, however, new studies are needed in order to clarify the oil's mechanism of action, as well as to identify its active constituents.

Infections by multiresistant microorganisms have led to a continuous investigation of substances acting as modifiers of this resistance. By following this approach, the chemical composition of the essential oil from Piper caldense leaf and its antimicrobial potential were investigated. The antimicrobial activity was determined by broth microdilution method providing values for minimum inhibitory concentration (MIC), IC50, and minimum fungicidal concentration (MFC). The essential oil was tested as a modulator for several antibiotics, and its effect on the morphology of Candida albicans (CA) strains was also investigated. The chemical characterization revealed an oil composed mainly of sesquiterpenes. Among them are caryophyllene oxide (13.9%), spathulenol (9.1%), &delta, cadinene (7.6%) and bicyclogermacrene (6.7%) with the highest concentrations. The essential oil showed very low activity against the strains of CA with the lowest values for IC50 and MFC of 1790 &mu, g/mL and 8192 &mu, g/mL, respectively. The essential oil modulated the activity of fluconazole against CA URM 4387 strain, which was demonstrated by the lower IC50 obtained, 2.7 &mu, g/mL, whereas fluconazole itself presented an IC50 of 7.76 &mu, g/mL. No modulating effect was observed in the MFC bioassays. The effect on fungal morphology was observed for both CA INCQS 40006 and URM 4387 strains. The hyphae projection was completely inhibited at 4096 &mu, g/mL and 2048 &mu, g/mL, respectively. Thus, the oil has potential as an adjuvant in antimicrobial formulations.

The Piper mikanianum species were investigated by the antimicrobial potential and chemical composition. Chemical analysis was performed by gas chromatography coupled to mass spectrometry (GC/MS). The Minimum Inhibitory Concentration (MIC) as well as the 50% Inhibitory Concentration against Candida strains were determined by microdilution. The effect of the drug-oil combination was also evaluated to verify possible synergism. The Minimum Fungicidal Concentration (MFC) was evaluated by subculturing the microdilution in Petri dishes and the anti-pleomorphism potential of the oil was tested in humid chambers. Chemical analysis revealed safrol as the major compound. The results from the intrinsic activity evaluation of the oil did not reveal a clinical importance, however, it presented a synergistic effect when associated with gentamicin against the multidrug resistant E. coli strain and when associated with fluconazole against fungal strains. Moreover, the oil possessed a fungistatic effect. Total inhibition of filamentous structures occurred in both Candida species in the anti-virulence test. The P. mikanianum essential oil showed a potentiating activity of drugs for which resistance exists and an inhibitory effect of one of the main virulence factors of the Candida genus, morphological transition, which has been previously shown to be responsible for causing invasive infections in human tissues.

Due to the biological properties associated to the Baccharis genus and the limited information on its antimicrobial properties, the present work investigates the chemical composition and antibacterial, antifungal and antiprotozoal activities of the essential oils of two species, B. uncinella from Campo Alegre and B. semiserrata from Atalanta, both places located in Santa Catarina State, Southern Brazil. Oils were obtained by hydrodistillation and were analyzed by gas chromatography–flame ionization detector (GC–FID) and GC–mass spectrometry (GC–MS). The dry leaf essential oil yield from B. uncinella was 0.65% (m/m), and 0.50% and 0.22% (m/m) for dry leaf and twig from B. semiserrata, respectively. The main components in the oil from B. uncinella were α-pinene (9.0%), β-pinene (9.2%), limonene (11.5%), β-caryophyllene (13.2%) and spathulenol (9.3%). The following major compounds were identified in the leaf essential oil from B. semiserrata: α-pinene (4.3%), β-pinene (11.4%), limonene (6.7%), β-caryophyllen...

In our continuous search for naturally occurring compounds of scientific and technological relevance, the chemical composition and antibacterial activity of the essential oils of two populations of Piper xylosteoides from Santa Catarina, Brazil, is described. Both oils showed a very high safrole concentration, being the highest value associated to the sample collected in Orleans (84.1%). As the second major compound, the monoterpene α-pinene was present with the highest concentration (15.3%) in the Sao Bonifacio sample. The antibacterial activity was examined towards both Gram-positive and Gram-negative bacteria. The oils showed weak activity against the bacteria tested. This species can be considered a new economically important natural source of the arylpropanoid safrole.

Essential oils have been extensively studied in recent years as a natural source of new antimicrobial agents. In this work, essential oils of leaf and branch from Drimys angustifolia growing in Southern Brazil were obtained by hydrodistillation and analyzed by gas chromatographies with flame ionization detector (GC-FID) and with mass spectrometer (GC-MS). Drimenol and bicyclogermacrene were isolated by column chromatography from branch and leaf essential oils, respectively. Oils, isolated compounds and combinations of them were assayed against Gram-(+) and Gram-(-) bacteria. The oils showed to be more active against Bacillus cereus, with minimum inhibitory concentration (MIC) 125 and 250 µg mL-1 for branch and leaf oils, respectively, strongly inhibiting bacterial growth. Bicyclogermacrene was more active then drimenol, providing a MIC value of 167 µg mL-1 against B. cereus. Synergism was not observed in any of the combinations tested. Nos últimos anos, os óleos essenciais vêm sendo intensamente estudados como fonte natural de novos agentes antimicrobianos. Neste trabalho, os óleos essenciais das folhas e galhos de Drimys angustifolia do sul do Brasil foram obtidos por hidrodestilação e analisados por cromatografias gasosas com detector de ionização de chama (GC-FID) e com espectrômetro de massa (GC-MS). Os constituintes drimenol e biciclogermacreno foram isolados por cromatografia em coluna do óleo essencial dos galhos e folhas, respectivamente. Os óleos, os constituintes isolados e combinações destes foram testados contra bactérias Gram-(+) e Gram-(-). Os óleos essenciais foram mais ativos contra Bacillus cereus, com MIC (concentração inibitória mínima) de 125 e 250 µg mL-1 para os galhos e folhas, respectivamente, inibindo fortemente o crescimento bacteriano. Biciclogermacreno foi mais ativo que drimenol, fornecendo um valor de MIC de 167 µg mL-1 contra B. cereus. Não foi observado qualquer efeito sinérgico nas combinações testadas.