Antibacterial and antifungal activity of selected medicinl plants available in Kerala

Abstract

In the present study cold ethanolic extract and fresh juice of five medicinal plants were screened for their in vitro antibacterial and antifungal activities. The plants were Annona squamosa (Aatha), Cassia alata (Anathakara), Coleus amboinicus (Panicoorka), Myristica fragrans (Nutmeg) and Tectona grandis (Teak). Antimicrobial activity was tested against Staphylococcus aureus subsp.aureus (MTCC 96), Salmonella enteritidis (MTCC 3219), Escherichia coli (MTCC 723), Pasteurella multocida subsp.multocida (MTCC 1161), Pseudomonas aeruginosa (MTCC 741), Aspergillus fumigatus (MTCC 870), Candida albicans (MTCC 227) and Cryptococcus neoformans var neoformans (MTCC 4404). Phytochemical analysis was conducted for the presence of routine secondary plant metabolites. The diameter of inhibitory zone at various concentrations of the extract, minimum inhibitory concentration (MIC), minimum bactericidal concentration (MBC) and minimum fungicidal concentration (MFC) were used to evaluate the in vitro antimicrobial activity of the above mentioned plants. Disc diffusion method, microtitre plate dilution technique and broth dilution technique were used. The reference drugs used in this study were penicillin G, furazolidone, ketoconazole and clotrimazole. The maximum yield was obtained from ethanolic extract of A. squamosa leaves (18.07 per cent). Leaves of C. amboinicus produced the maximum amount of fresh juice among the five plants (8 ml from 10 g of the fresh tender leaves). Phytochemical analysis reported the presence of steroids, alkaloids, tannins, flavonoids, glycosides, phenolic compounds, diterpenes, triterpenes and saponins in the leaves of A. squamosa and C. alata. Alkaloids, tannins, flavonoids, glycosides, steroids and saponins were present in the leaves of C. amboinicus. M. fragrans leaves contain glycosides, flavonoids, saponins and phenolic compounds. Qualitative chemical tests revealed the presence of tannins, flavonoids, glycosides, phenolic compounds and saponins in the leaves of T. grandis. All the extracts showed varying degrees of antimicrobial activity on the microorganisms tested. The antimicrobial screening revealed the susceptibility of E. coli to A. squamosa, C. amboinicus and T. grandis. The growth of S. aureus, P. multocida and P. aeruginosa was inhibited by all the five plants. S. enteritidis was found to be susceptible to T. grandis, M. fragrans and C. amboinicus. MIC values ranged from 200-1000 µg/ml and MBC values ranged from 500-1000 µg/ml. In case of A. squamosa, MBC value against E. coli was more than 1000 µg/ml. The antifungal screening revealed that the growth of C. albicans was inhibited by C. alata, C. amboinicus, M. fragrans and T. grandis. A. squamosa and C. alata inhibited the growth of C. neoformans. A. fumigatus appeared to be susceptible to A. squamosa, C. alata and C. amboinicus. MIC values ranged from 250-1000 µg/ml for the fungal strains. MFC values ranged between 500-1000 µg/ml except for A. squamosa and C. alata. MFC of C. alata against A. fumigatus and C. albicans was more than 1000 µg/ml. MFC of A. squamosa against C. neoformans was found to be more than 1000 µg/ml. The growth of S. aureus was inhibited by fresh juice of A. squamosa, C. amboinicus, M. fragrans and T. grandis leaves. E. coli was susceptible to fresh juice of C. amboinicus leaves. Fresh juice of C. alata was found to be effective against C. albicans. P. aeruginosa was inhibited by fresh juice of M. fragrans leaves. All the plants under the study were found to possess antimicrobial properties, thereby justifying their popular use in the treatment of infectious diseases caused by resistant microorganisms. Further study is required to assess the in vivo efficacy of these plants for the said action.