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The genus Callistemon belongs to the family Myrtaceae and comprises 34 species. They are woody aromatic trees or shrubs that are widely distributed in the wet tropics. According to the scientific literature, research on seed germination of this genus was rarely carried out. The germination requirements of Callistemon citrinus and Callistemon linearis were studied under controlled conditions in the laboratory. Seeds of both species were tested for germination at constant temperatures of 25°C, 30°C, 40°C, and at room temperature (23 ± 2°C) coupled with total darkness. Seeds were sown in Petri dishes (0.8% agar water) for 25 days of incubation. The kinetics of germination was determined according to four closely related parameters viz. final germination percentage (FGP), mean germination time (MGT), coefficient of velocity of germination (CVG) and time to 50% germination (T50). The room temperature of 23 ± 2 °C was found optimally suitable for both species, with 80% FGP and 11.1 days MGT for C. citrinus, and only 21.7% FGP and 12.4 days MGT were recorded for C. linearis. Furthermore, significant decrease in FGP was observed in both species at 25°C, 30°C and 40°C of temperature. The analysis also revealed that day 12-15 after seed sowing is suitable for final counts. Due of its very low FGP, seeds of C. linearis need an additional study to determine their viability.

Schistosomiasis is a chronic debilitating parasitic disease that causes hepatic damage and is known to be endemic in developing countries. Recent control strategies for schistosomiasis depend exclusively on chemotherapeutic agents, specifically praziquantel. Unfortunately, praziquantel has low efficacy in the early phase of infection, and resistance to treatment is increasingly reported. The aim of this work was to find an alternative treatment by assessing thein vivoactivity of aqueous extract ofCallistemon citrinusagainstSchistosoma mansoniin both prepatent and patent phases in experimentally infected mice. The study was conducted on 80 male BALB/c albino mice divided into eight groups.Callistemonwas administered at a dose of 200 mg/kg on days 14 and 45 post infection as a single therapy and in combination with praziquantel. Porto-mesenteric worm burden, hepatic and intestinal egg counts, hepatic granuloma number and diameter, and oogram pattern were assessed to evaluate the anti-schistosomal properties ofC. citrinus. Liver enzymes and total bilirubin were tested to assess hepatoprotective effects. Results revealed that the use ofC. citrinuswas associated with a significant decrease in worm burden and tissue egg load together with an increased percentage of dead eggs. In addition, there was a significant reduction in granuloma formation.Callistemonalso led to a significant improvement in liver function. The best results were obtained whenC. citrinuswas given in the prepatent phase of infection and when combined with praziquantel. Although the effects ofC. citrinusare considered to be promising, further studies using different extracts, active ingredients and doses are needed.

Introduced species lists provide essential background information for biological invasions research and management. The compilation of these lists is, however, prone to a variety of errors. We highlight the frequency and consequences of such errors using introduced Melaleuca (sensu lato, including Callistemon) species in South Africa as a case study. We examined 111 herbarium specimens from South Africa and noted the categories and sub-categories of errors that occurred in identification. We also used information from herbarium specimens and distribution data collected in the field to determine whether a species was introduced, naturalized and invasive. We found that 72% of the specimens were not named correctly. These were due to human error (70%) (misidentification, and improved identifications) and species identification problems (30%) (synonyms arising from inclusion of Callistemon, and unresolved taxonomy). At least 36 Melaleuca species have been introduced to South Africa, and field observations indicate that ten of these have naturalized, including five that are invasive. While most of the errors likely have negligible impact on management, we highlight one case where incorrect identification lead to an inappropriate management approach and some instances of errors in published lists. Invasive species lists need to be carefully reviewed to minimise errors, and herbarium specimens supported by DNA identification are required where identification using morphological features is particularly challenging.

Since ancient times, essential oils from medicinal plants have supplied a huge repository of secondary metabolites. Genus Callistemon, Myrtaceae, was described to have nematicidal, antithrombotic, antistaphylococcal, antioxidant, and insecticidal activities. In this study we investigate the chemical composition of essential oils from the leaves and the flowers of C. macropunctatus (Dum.Cours.) Court and Callistemon subulatus (Cheel) from two geographical locations: Australia and Egypt. GC MS analysis identified a total of sixty-one volatile components and showed that the major constituents were 1,8-cineole, α-pinene, α-terpineol, limonene and α-phellandrene in the leaves and α-pinene, 1,8-cineole, α-phellandrene, limonene and α-terpineol in the flowers of Callistemon species. To discriminate the oil complexity within factors as location, plant parts and species, principal component analysis (PCA) and hierarchical cluster analysis (HCA) were employed. Furthermore, the cytotoxic effect of the oil samples was assayed against the human liver cancer cell line HepG2 to reveal a potent anticancer potential with half-maximal inhibitory concentration (IC50) values ranging from 1.76 μg/mL to 13.41 μg/mL. To gain insight into the cellular mechanism of the cytotoxic activity, Callistemon volatile oils’ activities on topoisomerases I-β and II-β were explored, which demonstrated significant enzyme inhibition with IC50 values as low as 819.6 ng/mL. Molecular in-silico docking study of the major oil components within the active binding site of the human topoisomerases I-β and II-β was conducted. α-terpineol showed promising alkyl interactions in the binding pockets of topoisomerase I B and II B, with a docking Gibb’s free energy values of -27.0913 and -26.6478 kcal/mol, respectively. Whereas it bounded to Arg503 and four nucleotide regions deoxyadenosine DA12, deoxythymidine DT9, deoxyguanosine DG13, deoxycytidine DC8 in the topoisomerase II-β enzyme pocket, it interacted with Topo I-β enzyme through hydrophobic alkyl and Pi-alkyl binding interactions with DA12, DG13 and Arg503. Furthermore, the oxygen in the hydroxyl group showed two additional non-covalent bonds: a conventional hydrogen bond with Asp533 and water hydrogen bond with a water molecule in the vicinity of the binding surface. This research highlights the future possibility of having Callistemon subulatus as a potential natural drug for treatment of liver cancer.

Callistemon lanceolatus (Myrtaceae) plant claimed for the management and control of rice - moth Corcyra cephalonica an insect pest of stored commodities. When freshly laid eggs were exposed to Callistemon lan ceolatus oil volatiles for 12, 24, 48, and 72 h with 20, 40, 80 or 160 µ l of oils, a marked decline in egg hatchability in this pest was seen after exposure period. The oil having insecticidal properties w h ich was extracted by Clevenger apparatus in the laboratory by hydro - distillation process, subjected to Gas chromatography - mass spectrometry technique. The presence of active ingredients of Callistemon lanceolatus oils obtained at 0.001 % yield by hydro - distillation mainly consisted of 1, 8 Cineole*62.25 %; Alpha - terpineol*8.73; D - limonene*8.40 %; Alpha Pinene*7.03 %; Alpha Phellendrene*2.85 %; Linalool*0.67 % etc. The result offers a platform for using Callistemon lanceolatus leaf oils for control and management of rice moth Corcyra cephalonica in godo wns, warehouses around the world.

Plants are the source of a variety of secondary metabolites, which are often used in the anticancer activity. Discovering new anticancer drug from herbal source is more important in both biological and pharmacological activities. Hence, the objective of this study is to identify the anticancer agent in Callistemon citrinus (Curtis) Skeels (CC) for the treatment of cancer. Very recently we have reported an increased antioxidant activity in the ethanolic and methanolic extracts (EE and ME) of CC but significantly reduced activity (rather increased cytotoxicity), in the n-hexane extract (HE). In this study, the cytotoxicity of all the three solvent extracts was tested against A431, MG-63 and HaCaT cell lines by MTT assay. Interestingly HE has showed increased anti-proliferative effect against the cancer cells but was resisted by non-malignant cells. HPLC and GC-MS analysis revealed the presence of 1,8-Cineole as a predominant compound in HE, the semi-purified bioactive extract. Henceforth, this would be called HE-C and be used for further analyses to understand its mode of action on induced apoptosis/necrosis. Alamar blue assay of HE-C showed cytotoxicity and change in morphological characteristics, which was confirmed by AO/EB staining using fluorescence microscopy, ultra-structural features of apoptosis using SEM and TEM. HE-C induced cell death was also detected by FACS using FITC-labelled Annexin-V and Propidium iodide. ROS generation was monitored using DCF-DA by flow cytometry. The overall results suggested that the selective extract (HE-C) containing 1,8-Cineole has shown potential anti-cancer activity in a dose-dependent manner, and cell death was induced through ROS-mediated apoptosis. Our findings provide an insight into the potential of 1,8-Cineole as a novel drug for killing cancer cells.

Multidrug resistant Staphylococcus aureus poses a severe global threat worldwide due to their prevalence, genomic plasticity and limited therapeutic options being refractory to most antibiotic classes. This necessitates the discovery of new anti-staphylococcal interventions. Callistemon rigidus R.Br. (Myrtaceae) has been found to possess antibacterial potential against clinical isolates. Thied me study was a isolate and evaluate the antibacterial alkaloids from the leaves of Callistemon rigidus and assess their in vitro anti-staphylococcal potential. Alkaloid isolation was carried out by modiied method for plant alkaloid extraction. The in vitro anti-staphylococcal potential of the alkaloid bioactive fraction was assessed by using micro broth dilution and plate count assay methods. Pus and wound isolates had MIC of 80 µg/mL and 50 IC of 27.22 µg/mL respectively. Burn isolates showed MIC of 320 µg/mL and 50 50 13.57 µg/mL respectively. Urine and vaginal isolates exhibited a MIC of 80 µg/mL 50 and IC of 13.15 µg/mL respectively. Ceixime had MIC values was 320 µg/mL, 160 50 50 µg/mL and 160 µg/mL for pus and wound, burn, urine and vaginal isolates indicating the refractory behaviour when compared to alkaloid bioactive fraction from the leaves of Callistemon. The alkaloid bioactive fraction exhibits immense activity compared to standard antibiotic Ceixime. This work is the irst report of alkaloids and their antimicrobial activity from Callistemon rigidus leaves. The results suggest further isolation of individual alkaloids from alkaloid bioactive fraction and assessment their anti-staphylococcal activity as leads for development of anti-staphylococcal drugs.

Introduction: The genus Callistemon (family: Myrtaceae) contains 34 species which are widely distributed in the temperate regions and used in folk medicine. Methods: Chromatographic separation of 80% MeOH extract of the leaves of Callistemon viridiflorus (sims) Sweet (Cv) was performed. Results: Seven known polyphenolic compounds were isolated for the first time from this species: gallic acid, ellagic acid, isoquercetin, hyperin, 1,2:3,4-(bis(s)-hexahydroxy diphenoyl-β-D-glucopyranose, nilocitin and quercetin-3-O-α-L-glucuronopyranoside. The methanolic extract of Cv leaves exhibited a significant anti-microbial activity against the tested microorganisms.

Myrtaceae is one of the chemically most variable and most significant essential oil yielding plant families. Despite an abundance of chemical information, very little work has focussed on the biochemistry of terpene production in these plants. We describe 70 unique partial terpene synthase transcripts and eight full-length cDNA clones from 21 myrtaceous species, and compare phylogenetic relationships and leaf oil composition to reveal clades defined by common function. We provide further support for the correlation between function and phylogenetic relationships by the first functional characterisation of terpene synthases from Myrtaceae: a 1,8-cineole synthase from Eucalyptus sideroxylon and a caryophyllene synthase from Eucalyptusdives.

Preparation of an account of Melaleuca L. (Myrtaceae) for Flora of Australia resulted in the recognition of nine new species and three subspecies of Melaleuca. The following are newly described from Australia: from Queensland: M. hemisticta S. T. Blake ex Craven, M. lazaridis Craven, M. montis-zamiae Craven, M. phratra Craven, M. pyramidalis Craven, M. quercina Craven, M. viminalis (Solander ex Gaertner) Byrne subsp. rhododendron Craven, M. williamsii Craven subsp. fletcheri Craven; from New South Wales: M. megalongensis Craven & S. M. Douglas, M. serpentina Craven, M. williamsii subsp. synoriensis Craven; and from Queensland and New South Wales: M. sabrina Craven. The recently described Callistemon wimmerensis Marriott & G. W. Carr is transferred to Melaleuca as M. wimmerensis (Marriott & G. W. Carr) Craven.

The chemical composition and the antibacterial activity of the essential oils obtained by hydrodistillation from the leaves of Callistemon citrinus and Callistemon viminalis were analyzed by GC and GC/MS. Twenty-four and twelve components were identified for C. citrinus and C. viminalis, representing 92.0% and 98.3% of the total oils. The major components of C. citrinus and C. viminalis were 1,8-cineole (61.2% and 83.2%) and alpha-pinene (13.4% and 6.4%), respectively. The in vitro antibacterial activity of the essential oils was studied against 12 bacteria strains using disc diffusion and broth microdilution methods. The oils exhibited strong zone of inhibitions against some bacteria such as S. faecalis (20.3-24.0 mm), both strains of S. aureus (23.0-26.3 mm), B. cereus (17.3-19.0 mm) and S. macrcesens (11.3-23.7 mm) when compared to standard antibiotics gentamycin and tetracycline used as controls. Expect for P. aeruginosa and S. macrcescens, the MIC values of both essential oils ranged from 0.31-2.50 mg/mL.

The essential oil from the fresh leaves of Callistemon speciosus (Sims) DC. was isolated by hydrodistillation. Thirty-one volatile compounds (relative amount >0.1%) were separated and positively identified by GC (FID) and gas chromatography-mass spectrometry (GC/MS). Major constituents were 1,8-cineole (55%), α-pinene (19%), α-terpineol (4.1%), and α-phellandrene (3.0%). The oil presented a mean lethal concentration against Artemia franciscana of 56.7 μg/L and 39.8 μg/mL after 24 and 48 h exposition, respectively, and had a mild but significant effect on the crustacean elongation

The Australian species of the bottlebrush genus Callistemon R. Brown are not sufficiently distinct from Melaleuca L. for Callistemon to be maintained as a separate genus. The primary character states used to justify maintenance of Callistemon are that its staminal filaments are free and not grouped. This breaks down as fused filaments in five groups, the defining features of Melaleuca, occur in some Callistemon species. Therefore, it is concluded that the two genera should be combined. The following new names are proposed for species being treated in a forthcoming account of Melaleuca for Flora of Australia: M. faucicola Craven, M. flammea Craven, M. orophila Craven, M. paludicola Craven, M. salicina Craven, M. virens Craven, and M. williamsii Craven. The following new combinations are established as transferred from Callistemon: M. brachyandra (Lindley) Craven, M. chisholmii (Cheel) Craven, M. comboynensis (Cheel) Craven, M. flavovirens (Cheel) Craven, M. formosa (S. T. Blake) Craven, M. montana...

In vitro. investigation of the antimicrobial activity of a crude methanol extract of leaves of Callistemon rigidus. R.Br. (Myrtaceae) revealed potential antibacterial activity against a broad spectrum of multidrug-resistant human pathogens. Agar well diffusion assays of the test extract established significant concentration-dependent antibacterial activity against methicillin-resistant Staphylococcus aureus., vancomycin-intermediate Staphylococcus aureus., vancomycin-resistant Escherichia coli., extended spectrum β.-lactamase-producing E. coli., and multidrug-resistant Pseudomonas. spp.

Host range expansion in insect herbivores is often thought to be mediated by several factors, principal among them are secondary plant metabolites. In weed biological control, the host range of a prospective agent is one of the most important considerations in its implementation. Extensive host testing tests seek to determine the behavioral acceptance and nutritional value of different test plant species to the potential agent. A list of test plants is compiled that comprises species that are close taxonomic relatives of the target weed plus other species of economic or ecologic importance. The host testing of the Melaleuca quinquenervia biological control agent Oxyops vitiosa indicated that larvae would accept and complete development on the Australian target weed M. quinquenervia, two Australian ornamental species, Callistemon citrina, Callistemon viminalis (all Myrtaceae). However, the larvae did not complete development when fed a North American species Myrica cerifera (Myricaceae). The study reported here confirms these results and examines the nutritional and performance differences in O. vitiosa larvae fed leaves of these species. The leaf quality factors, percent moisture, percent nitrogen, toughness, and terpenoid content were related to larval survival, performance and digestive indices. The results indicate that plant quality among the Myrtaceae species was generally similar and correspondingly larval survival, performance and digestive indices differed little when larvae were fed leaves of these species. However, significant differences occurred in the plant quality of the North American M. cerifera compared with the Australian species which had leaves with the lowest percent moisture, lowest leaf toughness, highest percent nitrogen. This species, however, is not a physiological host as none of the neonates survived to pupate. When third instars were switched to M. cerifera from their normal host M. quinquenervia reductions were found in survival, biomass gain, digestive efficiency, and conversion of digested food to insect biomass. The marginal acceptance of this North American native plant in laboratory bioassays appears related to the terpenoid chemistry that has similarities to the taxonomically unrelated host M. quinquenervia. However, the high larval mortality corresponds to several novel terpenoids that are not present in the host. For weed biological control host testing these results indicate that M. cerifera is a poor host for O. vitiosa. Additionally, future test plant lists should include plants with secondary metabolites similar to the target weed as these compounds may constitute behavioral cues that are relevant to these specialized herbivores.

Research on the natural enemies of the Australian tree Melaleuca quinquenervia, a dominant, adventive weed of wetland habitats in south Florida, USA began in the late 1970s. Since then host-range tests have been conducted in Australia and Florida on three insect species: a weevil, a sawfly, and a psyllid. Herein we discuss the host-range studies of the psyllid, Boreioglycaspis melaleucae conducted in quarantine in Florida. Tests showed that the host range is very narrow, limited to one Melaleuca species, M. quinquenervia. One time, a few psyllids developed on a different species, Callistemon (=Melaleuca) citrinus, broad-leaf form, but repeated efforts to rear it again failed. In its Australian homeland, B. melaleucae has been collected on 5 closely related broad-leaved Melaleuca species including M. quinquenervia; it developed on 2 of 4 species tested, M. viridiflora (28%) and M. quinquenervia (37%). There was also 2% development on a 6th narrow-leaved Melaleuca species, M. nodosa. In the New World, there are no native Melaleuca species; in the United States, there is one introduced group, Callistemon (=Melaleuca), which is of commercial value and just one naturalized species, M. quinquenervia, which has no commercial value. Because of the near absence of Melaleuca species and B. melaleucae’s narrow host range and ability to severely damage or kill M. quinquenervia, we concluded that field release of B. melaleucae in south Florida would be safe. The first releases were made in February 2002.

Callistemon (Myrtaceae) is a plant genus native to Australia with many cultivars grown as ornamentals worldwide. Several orange larvae of an undescribed gall midge (Diptera: Cecidomyiidae) were found feeding within vegetative buds of Callistemon viminalis plants grown in a production greenhouse in Victoria, Australia. Infested buds stopped their development and, following the departure of larvae, turned necrotic. Pupation took place in the soil. Young potted plants were infested and severely retarded in their overall growth. The new species is described and named Dasineura callistemoni Kolesik sp. nov.

The Australian melaleuca tree, Melaleuca quinquenervia (Cav.) S. T. Blake (Myrtaceae), has naturalized in southern Florida,U.S.A., and is now one of that regions most important weeds.Primarily a weed of wetlands, it also infests neighboring drierareas. Current efforts to restore the South Florida ecosystem arethreatened by the continuing range expansion of melaleuca andother weeds. In an effort to supplement the current chemical andcultural control methods for melaleuca, a search for potentialbiological control agents was begun in Australia in 1986. Thesawfly, Lophyrotoma zonalis, was determined after extensive fieldand laboratory studies to have potential as a biological controlagent. Larvae of L. zonalis eat leaves and occasionally defoliatelarge trees in Australia. Host range studies were conducted in aFlorida quarantine facility with native and cultivated plantspecies. Multi-choice and no-choice oviposition tests wereconducted with 36 species in the Myrtaceae and with 18 species inother families. Larvae developed to prepupae and adults from theeggs oviposited on 23 species of Myrtaceae only on 3 species ofbottlebrushes, Callistemon. Medium-sized larvae were tested forfeeding on bouquets of plant cuttings and on potted plants. Theyare the stage that might wander from defoliated trees. Noticeablefeeding, but much less than on melaleuca, was restricted to theMyrtaceae, except for a few individual larvae that fed on waxmyrtle, Myrica cerifera. Medium-sized larvae became prepupae onlyon Melaleuca decora (73%) and on wax myrtle (10%). However,neither species received eggs in the oviposition tests. Thesestudies confirmed the narrow host range of L. zonalis aspreviously reported from field and laboratory studies inAustralia.

The Australian paperbark tree, Melaleuca quinquenervia (Cavier) S. T. Blake, is a serious economic and environmental pest in Florida. One of the most damaging insects found attacking M. quinquenervia during surveys for biocontrol agents in its home range (Australia) was the leaf-blotching bug Eucerocoris suspectus Distant (Hemiptera: Miridae). Adults and nymphs of E. suspectus feed on young leaves and shoots. Their feeding kills leaf tissue surrounding the feeding site, leaving a distinctive, brown, blotch scar. Laboratory host-range studies showed 6 nontarget plant species to be at risk from E. suspectus. However, our extensive field survey data indicate that none of these plants are used as field hosts by E. suspectus. We conducted 8 intensive field searches for E. suspectus feeding damage on >60 plant species at 6 sites. Damage was only noted on Melaleuca spp., except on 1 occasion, where minor feeding damage was found on 2 Lumnitzera racemosa trees adjacent to a more heavily damaged M. quinquenervia tree. Thus, although E. suspectus completed its life cycle on several plant species in the laboratory (albeit at a much lower level than on M. quinquenervia ), in the field, feeding damage is restricted to Melaleuca spp. in the M. leucadendra (L.) L. complex, and rarely, Callistemon spp. The narrow host-range, broad habitat tolerances, and extensive damage caused by this insect should make it a valuable biological control agent if released in Florida.

Essential oils were obtained by hydrodistillation of the leaves, flowers and fruits of Callistemon lanceolatus in 0.2–0.6%, 0.2% and 0.2% yield, respectively, and from the flowers and fruits of C. polandii in 0.1% and 0.1% yield, respectively. The oils were analyzed by a combination of column chromatography, GC and GC/MS. The leaf, flower and fruit oils of C. lanceolatus contained 1,8-cineole (41.1%) and α-pinene (11.6%); β-pinene (51.2%) and 1,8-cineole (11.7%); and 1,8-cineole (38.8%) and α-terpineol (15.7%), respectively. The flower and fruit oils of C. polandii contained α-pinene (16.2%) and β-pinene (45.8%); and 1,8-cineole (16.3%) and α-terpineol (13–5%), respectively.

The volatile leaf oil of Callistemon linearis (Schrader et Wendl.) Sweet (Myrtaceae) is predominantly monoterpenoid in character with 1,8-cineole accounting for 64% of the oil. Sesquiterpenoids make up less than 3% of the oil, spathulenol being the only significant one at 1.5% of the oil. A comparison of the chemistry of the volatile oils of Callistemon and of the closely related genus Melaleuca shows that the latter is the more varied one of the two, although Callistemon oils in general resemble 1,8-cineole-rich Melaleuca oils.

The composition of the water-distilled essential oil of Callistemon citrinus (Curtis) Skeels was determined by GC, GC/MS and GC/FTIR. The oil was found to be rich in 1,8-cineole (68.0%), α-pinene (12.8%) and α-terpineol (10.6%).

The thin waxy coatings on leaves of nine species of Callistemon, two of Melaleuca and one species of Metrosideros, have been studied for the occurrence of leaf surface flavonoids. The Callistemon species and Metrosideros robusta exhibit only C-methylated flavonoids, while O-methyl flavonoids were detected in Melaleuca huegelii. The new natural C-methyl flavonol, 5,7-dihydroxy-3,8,4'-trimethoxy-6-C-methylflavone, was isolated from Metrosideros robusta. The leaf wax of Callistemon coccineus contains the novel C-methylflavonoid, 5,4'-dihydroxy-8-C-methyl-7-methoxy flavanone. (C) 2000 Elsevier Science Ltd.

The oil obtained from both the leaves and flowers of Callistemon citrinus (Curtis) Sheels (syn. C. lanceolatus DC) was subjected to gas chromatographic analysis. Of the sixteen compounds identified, 1, 8-cineole and α-terpineol were found to predominate. Furthermore, quantitative variations were found between leaf and flower oils so that flower oils could be differentiated based on their richness in α-pinene (15.1–42.7% vs 0.6–3.2%) and their decrease in α-terpineol content (5.2–17.5% vs 31.0–31.9%).