Antibacterial activity of traditional Australian medicinal plants

Fifty-six ethanolic extracts of various parts of 39 plants used in traditional Australian Aboriginal medicine were investigated for their antibacterial activities against four Gram-positive (Bacillus cereus, Enterococcus faecalis, Staphylococcus aureus and Streptococcus pyogenes) and four Gram-negative (Escherichia coli, Klebsiella pneumoniae, Pseudomonas aeruginosa and Salmonella typhimurium) bacterial species. In a plate-hole diffusion assay, 12 extracts inhibited the growth of one or more of the bacteria, with five extracts showing broad spectrum antibacterial activity against Gram-positive bacteria. B. cereus was the most susceptible bacterium, with all 12 extracts displaying activity against this organism. Extracts from the leaves of Eremophila species (Myoporaceae) were the most active, with Eremophila duttonii exhibiting the greatest activity (against Gram-positive bacteria). The antibacterial effects of E. duttonii were further investigated by time-course growth assays which showed that significant growth inhibition was observed in cultures incubated in the presence of the extract within 1 h for B. cereus, E. faecalis and S. aureus and 2 h for S. pyogenes.     

Antimicrobial activities of southern Nepalese medicinal plants

In an ethnopharmacological screening of selected medicinal plants used in Nepal, methanol extracts from 20 plant species were assayed for activity against eleven strains of bacteria and four strains of fungi. Duplicate assays were conducted with and without exposure to ultraviolet (UV)-A radiation to test for light-activated or light-enhanced activity. Fifteen of the extracts showed activity against bacteria and fourteen showed activity against fungi. Five extracts were active only when exposed to UV-A light, and the antibiotic or antifungal effect of five extracts was enhanced upon exposure to light. Two of the most active extracts were from plants used to treat diarrhoea and dysentery. Bark from both Terminalia alata (Combretaceae) and Mallotus phillppensis (Euphorbiaceae) was active against Gram-positive and Gram-negative bacteria.     

Antimicrobial activity of some plants used for the treatment of livestock disease in the Eastern Cape,South Africa

Approximately 75% of rural livestock owners in the Eastern Cape province of South Africa use plants or plant based remedies to treat their livestock. Prominent among these plants are Combretum caffrum, Salix capensis and Schotia latifolia. Water, methanolic and acetonic extracts as well as decoctions of the three plants were screened against ten bacteria and five fungi. The results of the antibacterial assay indicated significant activity against all the Gram-positive bacteria tested with the minimum inhibitory concentrations ranging from 0.1 to 5.0 mg/ml. A few of the extracts showed minimal activity, but the majority of extracts were not active on the Gram-negative bacteria. Generally, all the extracts showed some antifungal activity against the five test fungi. Methanolic extracts exhibited higher fungal growth inhibition, whereas the water extracts showed the least inhibition. It was noteworthy that some water extracts promoted fungal growth.     

Further evaluation of Rwandan medicinal plant extracts for their antimicrobial and antiviral activities.

A total of 45 Rwandan plant extracts, belonging to 37 different plant species out of 21 families, were investigated for their antibacterial, antifungal, and antiviral properties. The plants were selected on the base of their ethnomedicinal use against infections and autoimmune diseases. From all the plant extracts tested, only Clematis hirsuta (leaves) showed a pronounced antifungal activity against Candida albicans and the dermatophytes Trichophyton rubrum, Epidermophyton floccosum, and Microsporum canis. Seven plant extracts showed a high antiviral activity against the DNA-virus Herpes simplex type 1, while five and three plant extracts were highly active against the RNA-viruses Coxsackie and Polio, respectively. Only Macaranga kilimandscharica (leaves) showed an interesting anti-measles activity, whereas Eriosema montanum (leaves) and Entada abyssinica (leaves) were highly active against Semliki forest virus. Some plant extracts showed an antibacterial activity against Gram-positive bacteria and Mycobacterium fortuitum, but none of them were active against the Gram-negative bacteria tested.     

Composition and antimicrobial activity of Achillea clavennae L. essential oil

The volatile constituents of Achillea clavennae L. (Asteraceae), rare plant of Europe, have been analysed using GC/MS. Twenty- five components making up 81.6% of the oil were characterized with camphor (29.5%), myrcene (5.5%), 1,8-cineole (5.3%), beta-caryophyllene (5.1%) and linalool (4.9%) being the major constituents. The essential oil was evaluated for antibacterial and antifungal activities. The screening of the antimicrobial activity of essential oil was conducted by a disc diffusion test against Gram-positive (Bacillus subtilis, Bacillus cereus, Staphylococcus aureus, Streptococcus faecalis), Gram-negative (Escherichia coli, Klebsiella pneumoniae, Pseudomonas aeruginosa, Proteus mirabilis) and fungal organisms (Aspergillus niger, Aspergillus fumigatus, Candida albicans). The activity was more pronounced against Gram-negative and fungal organisms than against Gram-positive bacteria. A. clavennae oil was found to possess antimicrobial activity against Klebsiella pneumoniae, Pseudomonas aeruginosa and all fungal organisms.     

The efficiency of random versus ethno-directed research in the evaluation of Sinai medicinal plants for bioactive compounds

Hexane, ethyl acetate and ethanol extracts of sixty plant species (growing wild in Sinai, Egypt) were screened for antibacterial and antifungal activities against a range of Gram-positive and Gram-negative bacteria, a yeast and dermatophytic fungi. Plants were collected either by random or ethno-directed methods. Plants collected at random (36 species) were gathered from different districts of Sinai, while the ethnobotanical collection (24 species) comprised species used in the folk medicine of the Bedouins in Sinai. Results indicate that plant sampling based on ethnobotanical approach produced greater number of plants showing antimicrobial activity. The results are discussed with respect to the ethnobotanical correlation of active species.     

Antimicrobial activity of saponins from Medicago sp.: structure-activity relationship

The antimicrobial activity of saponins from Medicago sativa, M. arborea and M. arabica against a selection of medically important yeasts, Gram-positive and -negative bacteria was investigated. Structure-activity growth inhibitory effects of related prosapogenins and sapogenins are also described. Increasing antibiotic activity was observed going from the saponin extracts to the sapogenin samples, suggesting that the sugar moiety is not important for the antimicrobial efficacy. Activity was especially high against Gram-positive bacteria (Bacillus cereus, B. subtilis, Staphylococcus aureus and Enterococcus faecalis) with M. arabica being the species showing a broader spectrum of action. Discrete antifungal activity was also observed, mainly against Saccharomyces cerevisiae. The observed antimicrobial properties of M. sativa and M. arborea were related to the content of medicagenic acid, while hederagenin seems to contribute to the bioactivity of M. arabica total sapogenins.     

Antimicrobial activity of certain Indian medicinal plants used in folkloric medicine

Fifty medicinal plants belonging to 26 families were studied for their antimicrobial activity. Among 50 plants tested, 72% showed antimicrobial activity. About 22 plant extracts from 15 families exhibited activity against both Gram-positive and Gram-negative bacteria. Fourteen plants belonging to 11 families did not show activity against any of the bacteria tested. Only nine plant extracts showed antifungal activity. The bulb extracts of A. cepa and A. sativum exhibited activity against both filamentous and non-filamentous fungus. Eight plant extracts belonging to seven families exhibited both antibacterial and antifungal activity.     

Antibacterial, anti-inflammatory, anti-cholinesterase and mutagenic effects of extracts obtained from some trees used in South African traditional medicine

Extracts obtained from 10 trees used in South African traditional medicine were screened for antibacterial, anti-inflammatory (COX-1 and COX-2) and anti-cholinesterase activities and investigated for potential mutagenic effects using the Ames test. Antibacterial activity was detected using the disc-diffusion and micro-dilution assays. The extracts were tested against Gram-positive bacteria: Bacillus subtilis, Staphylococcus aureus, Micrococcus luteus and Gram-negative bacteria: Escherichia coli and Klebsiella pneumoniae. Of the 78 different plant extracts investigated, 80% showed activity against both Gram-positive and Gram-negative bacteria in the disc-diffusion assay. In the micro-dilution assay, 60% of the plant extracts showed minimum inhibitory concentration (MIC) values < or =1.56 mg ml(-1). The lowest MIC value (0.092 mg ml(-1)) was recorded for an ethyl acetate root extract of Acacia sieberiana against Staphylococcus aureus and Escherichia coli. In the anti-inflammatory assay, 70% of the investigated plant extracts (0.25 mg ml(-1)) inhibited both COX-1 and COX-2 activity (>50% and 70% for water and organic solvent extracts, respectively). An ethyl acetate leaf extract of Trichilia dregeana showed selective inhibition of COX-2 (81%). In the acetylcholinesterase inhibitory test, 21% of the plant extracts were active at a concentration < or =1 mg ml(-1) using the micro-dilution assay. The lowest IC(50) value was 0.04 mg ml(-1) obtained with an ethanol bark extract of Combretum kraussii. None of the investigated plants showed any potential mutagenic effects.     

Screening of some Cuban medicinal plants for antimicrobial activity

The antimicrobial activities of 23 extracts of 12 Cuban plant species reported in traditional medicine were tested. The agar diffusion method was used to assess the activity against four bacteria and one yeast: Staphylococcus aureus, Bacillus subtilis, Escherichia coli, Pseudomonas aeruginosa and Candida albicans. The results, evaluated as the diameter of the inhibition zone of microbial growth, showed that nine extracts were active against Gram-positive bacteria but only two of these proved to be also active against Gram-negative bacteria. None of the extracts inhibited the growth of the yeast. The most susceptible bacterium was Staphylococcus aureus and the best antibacterial activity was shown by Schinus terebenthifolius.     

Antibacterial and antifungal activity of Cassia fistula L.: an ethnomedicinal plant

Hexane, chloroform, ethyl acetate, methanol and water extracts from the flower of Cassia fistula (an ethnomedicinal plant) were tested against bacteria and fungi. All the extracts exhibited antibacterial activity against Gram-positive organisms with minimum inhibitory concentrations (MIC) between 0.078 and 2.5 mg/ml. Among the Gram-negative bacteria, only Pseudomonas aeruginosa was susceptible to the extracts. Ethyl acetate crude extract was fractionated using chromatographic techniques. A crystal was isolated, which was confirmed as 4-hydroxy benzoic acid hydrate using X-ray crystallography. It exhibited antifungal activity against Trichophyton mentagrophytes (MIC 0.5 mg/ml) and Epidermophyton floccosum (MIC 0.5 mg/ml).     

Antimicrobial activity of extracts of eastern North American hardwood trees and relation to traditional medicine

Wood and bark extracts of 14 eastern North American hardwood tree species which were used traditionally as medicine by First Nation's people were screened for antimicrobial activities with eight strains of bacteria and six strains of fungi. Eighty-six percent of the bark extracts were active against methicillin sensitive Staphylococcus aureus; 71% against Bacillus subtilus and 79% against Mycobacterium phlei. The bark extract of Juglans cinerea was active against Pseudomonas aeruginosa 187, Salmonella typhiumurium, and Klebsiella pneumoniae. The wood extracts were less active: 72% were active against S. aureus (methicillin-sensitive), 36% against B. subtilus and 43% against M. phlei. Results from antifungal tests indicated that 36% of the extracts were active against at least one fungal strain and that bark extracts were more active than wood extracts. The bark extract from Juglans cinerea had the broadest spectrum of activities against Candida albicans, Saccharomyces cerevisiae, Cryptococcus neoformans, Trichophyton mentagrophytes, Microsporum gypseum, and Aspergillus fumigatus. In general, the extracts were more active against gram positive bacteria than gram negative bacteria and against filamentous fungi than yeast-like fungi. The study also demonstrated a correlation between frequency of traditional medicinal use by the First Nations people and antimicrobial activity of extracts indicating that the traditional knowledge encompasses an understanding of aspects of chemical ecology.     

Antiviral and antimicrobial activities of Colombian medicinal plants

Strong antiviral and antimicrobial activities were detected in methanolic extracts of 24 plants used medicinally in the treatment of skin infections in four different regions of Colombia. Thirteen extracts displayed activity against herpes simplex virus (HSV) whereas none was active against poliovirus. The antiviral activity was indicated by a total inhibition of viral cytopathic effects (CPE) at a non-cytotoxic concentration of the extract. The most potent extract was obtained from Byrsonima verbascifolia (L.) HBK. which showed anti-HSV activity at a concentration as low as 2.5 microg/ml. Antimicrobial screening was conducted using the disc diffusion assay against Klebsiella pneumoniae, Escherichia coli, Streptococcus faecalis, Mycobacterium phlei, Bacillus subtilis, Staphylococcus aureus, Pseudomonas aeruginosa, Salmonella typhimurium and the human pathogenic yeast, Candida albicans. Anti-Candida activity was observed for Piper lanceaefolium HBK. and Juglans neotropica Diels. Twenty-two extracts displayed activity against Gram-positive bacteria whereas none was active against the Gram-negative species. We concluded that these Colombian medicinal plants represent an untapped source of potentially useful antivirals and are worthy of further study.     

Antimicrobial studies on three species of Hypericum from the Canary Islands

The antimicrobial activity of several extracts and fractions of the aerial parts of Hypericum canariense, Hypericum glandulosum and Hypericum grandifolium was investigated using the disc diffusion and broth microdilution methods against twelve reference microorganisms (eight bacterial and four fungal strains). The methanol extract and chloroform fraction of H. canariense, as well as the methanol extracts, butanol and chloroform fractions of both H. glandulosum and H. grandifolium exhibited a good antibacterial activity against four Gram-positive bacteria (Bacillus cereus var. mycoides, Micrococcus luteus, Staphylococcus aureus and Staphylococcus epidermidis) and the Gram-negative bacterium Bordetella bronchiseptica with the diameters of growth inhibition area in the range 10-25 mm and MICs values between 0.03 and 0.29 mg/ml. Neither the infusions and aqueous fractions of the species studied nor the butanol fraction of H. canariense showed any antibacterial activity against the tested microorganisms. Amongst the active extracts, the minimum inhibitory concentration (MIC) determination showed that the H. canariense chloroform fraction was the most active against M. luteus, S. aureus and S. epidermidis. No antifungal activity was seen with any of the extracts or fractions tested. The results of this study support the use of these species in Canarian traditional medicine to treat skin infections.     

Antimicrobial activity of some medicinal plants of the island Soqotra

Twenty-five selected plants belonging to 19 families were collected from different localities of the island Soqotra, dried and extracted with the solvents chloroform, methanol and hot water to yield 80 extracts. The extracts were tested for their antimicrobial activity against several Gram-positive and Gram-negative bacteria and against one yeast species using agar diffusion method. Antibacterial activity was demonstrated especially against Gram-positive bacteria including multiresistant Staphylococcus strains. The greatest activity was exhibited by the methanolic extracts of Boswellia elongata, Boswellia ameero, Buxus hildebrandtii, Commiphora parvifolia, Jatropha unicostata, Kalanchoe farinacea, Pulicaria stephanocarpa, Punica protopunica, Withania adunensis and Withania riebeckii. Only the methanolic extract of Buxus hildebrandtii displayed significant antifungal activity.     

Screening for anti-infective properties of several medicinal plants of the Mauritians flora

Several plants of the Mauritian flora alleged to possess anti-infective properties were studied against different strains of pathogenic bacteria and fungi. The grounded dried plant materials were extracted with different extractants and screened for anti-microbial activity using the disk diffusion and the micro-dilution techniques. Preliminary screening revealed that the methanol extracts were most active. Salmonella enteritidis, Enterobacter cloacae and Bacillus subtilis were the three test organisms, which were found to be susceptible to all the crude methanolic extracts of the different plants investigated (100% susceptibility), followed by Escherichia coli (57.1%) and Pseudomonas aeruginosa (57.1%), and Staphylococcus aureus (28.6%). The lowest minimum inhibitory concentration recorded for the different crude methanol extracts against Staphylococcus aureus, Escherichia coli, Salmonella enteritidis, Enterobacter cloacae, Bacillus subtilis and the mould fungus Candida albicans were 500, 1000, 125, 250, 1000 and 125 micro g/ml, respectively. Bioautography using Cladosporium cucumerinum revealed that dichloromethane (DCM) extracts had the highest activity against the phytopathogenic fungus. It was also noted that the DCM extracts of Michelia champaca and Antidesma madagascariense yielded the maximum number of growth inhibiting compounds against Cladosporium cucumerinum. Activity of the different crude extracts was also investigated against several phytopathogenic filamentous fungi, Colletotrichum glocosporoides, Rhizoctonia solani, Sclerotinia sclerotium, Guignardia sp. and Fusarium oxysporum. It was found that crude hexane extracts as well as crude DCM extracts exhibited marked activity against several strains of fungi, especially Colletotrichum glocosporoides, Sclerotinia sclerotium and Guignardia sp.     

Antioxidant, antimicrobial and cytotoxic activities of selected medicinal plants from Yemen

Ninety crude extracts, including dichloromethane, methanol and aqueous extracts from 30 medicinal plants used in the Yemeni ethnomedicine to treat common infections, were screened in vitro for antimicrobial activities against three Gram-positive bacteria and two Gram-negative bacteria, Candida maltosa and five opportunistic human fungal pathogens (two yeasts, three hyphomycetes). Most of the plants showed antibacterial activities. Extracts from Tamarindus indica flowers and Ficus vasta fruits have been the most active. Of the 30 plants tested, 13 showed antifungal activity (40%) against one ore more human pathogenic fungi. The strongest inhibition was exhibited by Azima tetracantha (fruits), Sansevieria ehrenbergii (fruits) and Solanum incanum (fruits). Ten methanol extracts, especially those of Acacia asak barks and Solanum nigrum fruits, showed effective free radical scavenging activities in the DPPH assay. Remarkable cytotoxic activity against FL-cells was shown only for five plants, among them Plicosepalus curviflorus (stems).     

Screening of some Tanzanian medicinal plants from Bunda district for antibacterial, antifungal and antiviral activities

Extracts from 50 plant parts obtained from 39 different plants belonging to 22 families used to treat infectious diseases in Bunda district, Tanzania, were screened against twelve microorganisms, including the bacteria Bacillus cereus, Staphylococcus aureus, Escherichia coli, Pseudomonas aeruginosa, Klebsiella pneumoniae and Salmonella typhimurium, the fungi Aspergillus niger, Candida albicans, and the viruses Herpes Simplex Virus type 1, Vesicular Stomatitis Virus T2, Coxsackie B2 and Semliki Forest A7. The highest activity was obtained for the n-hexane extract of Elaeodendron schlechteranum root bark against the Gram-positive bacteria Bacillus cereus (MIC 0.97 microg/ml and MBC 1.95 microg/ml) and Staphylococcus aureus (MIC 3.90 microg/ml and MBC 31.25 microg/ml). Gram-negative bacteria were less sensitive. Only Balanites aegyptiaca stem bark exhibited a high antifungal activity against Candida albicans (MIC 125 microg/ml and MFC 250 microg/ml). Extracts from four plants; Lannea schweinfurthii, Combretum adenogonium, Ficus sycomorus and Terminalia mollis showed strong antiviral activity with RF values of 10(3) and 10(4) against Herpes Simplex Virus type 1 at various concentrations. Our results support, at least in part, the use of most plants as claimed by traditional healers/informants especially against the Gram-positive bacteria Bacillus cereus and Staphylococcus aureus.     

Antimicrobial activity of some coumarin containing herbal plants growing in Finland

Antimicrobial screening against selected Gram-positive and Gram-negative bacteria, yeasts, mold, as well as plant pathogenic fungi, with emphasis on method optimization was carried out on methanol extracts prepared from seven plants grown in Finland. Sensitivity to the extracts was found to vary considerably among the micro-organisms, the extract from Petroselinum crispum and Ruta graveolens showing the highest toxicity against Rhizoctonia solani. The growth of Heterobasidium annosum was inhibited, whereas that of Phytophtora (cactorum) was promoted by all the extracts. The antibacterial and antifungal activities of six natural coumarin compounds were weak, except for the inhibitory effect against Fusarium culmorum.     

Antimicrobial activity of the crude extracts and compounds from Ficus chlamydocarpa and Ficus cordata (Moraceae)

The aim of this study was to evaluate the antimicrobial activity of the methanol extracts from Ficus chlamydocarpa (FCR), Ficus cordata (FCB), mixture of the two plants (FCM), as well as that of the isolated flavonoids Alpinumisoflavone (2), Genistein (3), Laburnetin (4), Luteolin (5) (isolated from FCR), Catechin (7) and Epiafzelechin (8) (isolated from FCB). Mycobacteria, fungi, Gram-positive and Gram-negative bacterial species were tested for their susceptibility to the above samples. The microplate dilution and radiometric respiratory methods were used to determine the susceptibility testing of the samples against Mycobacterium smegmatis and Mycobacterium tuberculosis, respectively. The disc diffusion assay was used to determine the sensitivity of the samples, whilst the micro-dilution method was used for the determination of the minimal inhibition concentration (MIC) and the minimal microbicidal concentration (MMC) against fungi, Gram-positive and Gram-negative bacterial species. All the samples except compound 7 were found to be active to Mycobacterium smegmatis and the MIC ranged from 0.61 to 312.50microg/ml. Compound 4 showed the best activity against Mycobacterium tuberculosis exhibiting an MIC of 4.88microg/ml. The results of the diffusion test indicated that the crude extract from FCB, FCM as well as compounds 5 and 8 were able to prevent the growth of all tested (fungi, Gram-positive and Gram-negative bacteria) organisms. The inhibition effect of the crude extract from Ficus chlamydocarpa was observed on 10 (62.5%) of the 16 tested microorganisms (excluding mycobacteria) whereas that of compounds 4, 2 and 3 was respectively noted on 14 (87.5%), 8 (50.0%) and 7 (39.9%) of the tested microbial species. FCB was found to be more active than FCR on most of the tested organisms. The results provided evidence that the studied plants extract, as well as some of the isolated compounds might be potential sources of new antimicrobial drug.