Search for antibacterial and antifungal agents from selected Indian medicinal plants

A series of 61 Indian medicinal plants belonging to 33 different families used in various infectious disorders, were screened for their antimicrobial properties. Screening was carried out at 1000 and 500 microg/ml concentrations by agar dilution method against Bacillus cereus var mycoides, Bacillus pumilus, Bacillus subtilis, Bordetella bronchiseptica, Micrococcus luteus, Staphylococcus aureus, Staphylococcus epidermidis, Escherichia coli, Klebsiella pneumoniae, Pseudomonas aeruginosa, Streptococcus faecalis, Candida albicans, Aspergillus niger and Saccharomyces cerevisiae. Twenty-eight plant extracts showed activity against at least one of the test organisms used in the screening. On the basis of the results obtained, we conclude that the crude extracts of Dorema ammoniacum, Sphaeranthus indicus, Dracaena cinnabari, Mallotus philippinensis, Jatropha gossypifolia, Aristolochia indica, Lantana camara, Nardostachys jatamansi, Randia dumetorum and Cassia fistula exhibited significant antimicrobial activity and properties that support folkloric use in the treatment of some diseases as broad-spectrum antimicrobial agents. This probably explains the use of these plants by the indigenous people against a number of infections.     

Antimicrobial properties of Phrygilanthus acutifolius

Ethanol extract of flowers of Phrygilanthus acutifolius (Ruiz & Pav.) Eichler (Loranthaceae) inhibited the growth of both Gram (+) bacteria (Staphylococcus aureus, Staphylococcus saprophyticus and Enterococcus faecalis) and Gram (-) bacteria (Serratia marcescens, Acinetobacter sp. and Pseudomonas aeruginosa). This extract was bactericidal against Staphylococcus aureus and bacteriostatic against Pseudomonas aeruginosa. Morphological evidence suggests that the extract causes the swelling of the bacterial body of Staphylococcus aureus, the disintegration of the cell surface and the cell death. Bactericidal activity was optimal at pH 7.5 and was not affected by different ionic strengths. The presence of Mg2+ in the culture medium of Phrygilanthus acutifolius diminished the sensitivity of Pseudomonas aeruginosa strain against the extract. Test results would tend to corroborate the folk belief that the flowers of this plant are efficacious against respiratory infections and would justify its further investigation.     

Wound healing, anti-microbial and antioxidant potential of Dendrophthoe falcata (L.f) Ettingsh

Dendrophthoe falcata (L.f) Ettingsh (Loranthaceae) of the order Santalales, is used ethnomedicinally for treating ulcers, asthma, impotence, paralysis, skin diseases, and wounds. In this context, validations of the ethnotherapeutic claims of the plant in wound healing activity was studied, besides anti-microbial activity and antioxidant activity were performed to understand the mechanism of wound healing potency. The ethanolic extract of aerial parts of Dendrophthoe falcata ethanolic extract (DFEE) was investigated for the evaluation of its healing efficiency on excision and incision wound models in rats. The results showed that Dendrophthoe falcata extract has potent wound healing capacity as evident from the wound contraction and increased tensile strength. Hydroxyproline and hexosamine expressions were also well correlative with the healing pattern observed. Three of the fractions A-C (petroleum ether, chloroform and ethanol, respectively) obtained from the extract exhibited significant antimicrobial activity against the organisms: Staphylococcus aureus, Staphylococcus pyogenes, Staphylococcus epidermidis, Micrococcus luteus, Bacillus subtilis, Bacillus cereus, Klebsiella pneumoniae, Enterobacter aerogenes, Pseudomonas aeroginosa, Serratia marcescens, and five fungi Candida albicans, Candida tropicalis: dimorphic fungi, Aspergillus fumigatus, Aspergillus niger: systemic fungi, and some infectious bacteria Escherichia coli, and Salmonella typhi. The results also indicated that DFEE possesses potent antioxidant activity by inhibiting lipid peroxidation, reduced glutathione, superoxide dismutase levels and increased the catalase activity.     

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.     

Screening of medicinal plants of Rwanda (Central Africa) for antimicrobial activity

A series of 100 medicinal plants of Rwanda (282 plant samples) has been screened for antimicrobial activity against Bacillus subtilis, Candida albicans, Mycobacterium smegmatis, Pseudomonas aeruginosa, Salmonella gallinarum and Staphylococcus aureus. Thirty percent of the plants tested showed activity against one or more microorganisms.     

Antimicrobial and antioxidant activities of traditional Thai herbal remedies for aphthous ulcers

Four medicinal plants (Quercus infectoria, Kaempferia galanga, Coptis chinensis and Glycyrrhiza uralensis) as well as one traditional Thai treatment for aphthous ulcers based on these four plants were tested for antimicrobial activity. MIC values for a range of bacteria and Candida albicans were determined, with both type strains and clinical isolates being used. Antioxidant activity was determined using the ABTS radical scavenging assay. Among the four plants, Q. infectoria showed antimicrobial activity against Staphylococcus aureus with an MIC of 0.41 mg/mL, while C. chinensis showed antifungal activity against C. albicans with an MIC of 6.25 mg/mL. Activity was also shown against a range of other organisms including Salmonella typhi, Serratia marcescens, Vibrio cholerae, Vibrio parahaemolyticus, Pseudomonas aeruginosa and Enterococcus faecalis. The antimicrobial activity of the traditional aphthous ulcer preparation (a powder) was comparable to that for the individual plant extracts, however, incorporation of the powder into a gel formulation resulted in the loss of almost all activity. All extracts, with the exception of K. galanga, also showed good antioxidant activity. This study supports the traditional use of these plants and suggests that they may also be useful in the treatment of other infections.     

Antibacterial activity of some folklore medicinal plants used by tribals in Western Ghats of India

A series of 30 Indian folklore medicinal plants used by tribal healers to treat infections, were screened for antibacterial properties at 10 mg/ml concentration by using disc diffusion method against Bacillus subtilis, Escherichia coli, Klebsiella aerogenes, Proteus vulgaris, Pseudomonas aerogenes and Staphylococcus aureus. Twenty plant species showed activity against one or more species of bacteria used in this assay; among them the leaf extracts of Cassia occidentalis and Cassia auriculata exhibited significant broad spectrum activity against B. subtilis and S. aureus. Ten plant species were not found active against all tested bacteria. These results were compared with results obtained using standard antibiotics, chloramphenicol (30 microg/disc) and streptomycin (30 microg/disc) which served as a reference for inhibition zone diameter.     

Screening of some Siberian medicinal plants for antimicrobial activity

The antimicrobial activity of crude ethanolic extracts of 16 Siberian medicinal plants was tested against five species of microorganisms: Bacillus cereus, Escherichia coli, Staphylococcus aureus, Pseudomonas aeruginosa, and Candida albicans. Of the 16 plants tested, 12 showed antimicrobial activity against one or more species of microorganisms. The most active antimicrobial plants were Bergenia crassifolia, Chelidonium majus, Rhaponticum carthamoides, Sanguisorba officinalis, and Tussilago farfara.     

Antimicrobial activity of Streblus asper leaf extract

Bactericidal activity was found in the 50% ethanol (v/v) extract of Streblus asper leaves. The extract possessed a selective bactericidal activity towards Streptococcus, especially to Streptococcus mutans which has been shown to be strongly associated with dental caries. The extract had no effect on cultures of Escherichia coli, Staphylococcus aureus and Pseudomonas aeruginosa, Staphylococcus coagulase positive, Staphylococcus coagulase negative, Serratia marcescens, Klebsiella pneumoniae, Enterobacter, Pseudomonas aeruginosa, Burkholderia pseudomeallei and Candida albicans. The minimum growth inhibitory concentration and the minimum bactericidal concentration of S. asper extract against 10(8) CFU/mL of S. mutans was 2 mg/mL. The active compound is partially polar, partially heat labile, precipitated by 80% ammonium sulphate, and possesses a molecular weight larger than 10 000 Da. The potential for using S. asper extract as a natural product for controlling dental caries is discussed.     

Antimicrobial activities of the stembark of Kigelia pinnata.

Chemical investigation showed that the aqueous extracts of the stembark of Kigelia pinnata contain iridoids as major components. In the light of the traditional uses of this plant, antimicrobial activities of the aqueous extracts and two major iridoids were tested against Bacillus subtilis, Escherichia coli, Pseudomonas aeruginosa, Staphylococcus aureus and Candida albicans. The crude aqueous extracts showed significant antimicrobial activity which could be partially explained by the activity of the iridoids present.