25 N Save Nature to Survive 6(1) : 25-28, 2011 www.thebioscan.in ANTIMICROBIAL ACTIVITY OF THREE INDIAN MEDICINAL PLANTS – AN IN VITRO STUDY K. J. UMADEVI, V. VANITHA, AND K. VIJAYALAKSHMI* Department of Biochemistry, Bharathi Women’s College, Chennai - 600 108, T.N. E-mail: umaishaa@gmail.com INTRODUCTION Infectious diseases are the leading cause of death world-wide. For a long period of time plants have been valuable sources of natural products for maintaining human health, especially in the last decade, with more intensive studies for natural therapies. The use of plant compounds for pharmaceutical purposes has gradually increased in India. Many works have been done which aim at knowing the different antimicrobial and phytochemical constituents of medicinal plants using them for the treatment of microbial infections as possible alternatives to chemically synthetic drugs to which many infectious microorganisms have become resistant. During the last ten years the pace of development of new antimicrobial drugs has slowed down while the prevalence of resistance has increased astronomically (Hugo and Russell, 1984). Literature reports and ethnobotanical records suggest that plants are the sleeping giants of pharmaceutical industry (Hostettmann and Hamdurger, 1991). Natural products, either as pure compound or as standardized plant extracts, provide unlimited opportunities for new drug leads, because of the unmatched availability of chemical diversity. There is continuous and urgent need to discover new antimicrobial compounds with diverse chemical structures and novel mechanisms of action for new and re- emerging infectious diseases (Rojas et al., 2003). Therefore, researchers are increasingly turning their attention to folk medicine, looking for new leads to develop better drugs against microbial infections. The increasing failure of chemotherapeutics and antibiotic resistance exhibited by pathogenic microbial infectious agents has led to the screening of several medicinal plants for their potential antimicrobial activity (Colombo and Bosisio, 1996). In recent years, secondary plant metabolites (phytochemicals), previously with unknown pharmacological activities, have been extensively investigated as a source of medicinal agents (Krishnaraju et al., 2005). Thus it is anticipated that phytochemicals with adequate antibacterial efficacy can be used for the treatment of bacterial infections (Balandrin et al., 1985). Since time immemorial, it has been suggested that ethanolic extract from plants used in allopathic medicines are potential sources of antiviral, antitumoral and antimicrobial agents (Negi et al., 1993). Annona squamosa Linn, commonly known as Sugar apple, belonging to the family Annonaceae, is said to show varied medicinal effects, including insecticide, antiovulatory and abortifacient. A bark is used to prevent diarrhoea, the root is used in the treatment of dysentery. A decoction of the leaves is used for cold and to clarify urine, to treat hysteria and fainting spells (Asolkar et al., 1992). The fruits of Annona are haematinic, cooling, sedative, stimulant, expectorant, maturant tonic. The bark and leaves contain annonaine, an alkaloid (Vohora et al., 1975) which is found to posses many of these properties. Aegle marmelos, commonly known as bael, is a spiny tree belonging to the family Rutaceae. The leaves, roots, bark, seeds and fruits of Aegle marmelos are edible. The medicinal properties of this plant have been described in the Ayurveda. In fact, as per Charaka (1500 B.C.), no drug has been longer or ABSTRACT The alcoholic leaf extract of the three Indian medicinal plants Annona squamosa, Aegle marmelos and Citrus limon were screened for its antimicrobial activity using disc diffusion method. They were tested against four gram positive bacteria (Staphylococcus aureus, Staphylococcus epidermidis, Bacillus cereus, Bacillus subtilis), three gram negative bacteria (Escherichia coli, Pseudomonas aeruoginosa, Klebsiella pneumonia) and against three fungi (Aspergillus niger, Aspergillus fumigates,Candida albicans). It was observed that all the three alcoholic leaf extracts showed antibacterial and antifungal activity. The alcoholic leaf extract of Annona squamosa was found to be most active against S. aureus, B. cereus, K. pneumonia, A. niger and A.fumigates. The alcoholic leaf extract of Aegle marmelos was found to be active against B. subtilis, E. coli, P.aeuroginosa and C. albicans. The alcoholic leaf extract of Citrus limon was most active against S.epidermidis and E. coli. The susceptibility of the microorganisms to the extracts of these plants was compared with each other and with the standard antibiotics ciprofloxacin and ketoconozole. The antimicrobial activities of the three alcoholic leaf extracts are discussed according to their phytochemical components. It is concluded that these three Indian medicinal plants may serve as a valuable source of compounds with therapeutic potential. KEY WORDS Antimicrobial activity Annona squamosa Aegle marmelos Citrus limon Received on : 27.09.2010 Accepted on : 18.12.2010 *Corresponding author