Int. J. Pharm. Sci. Rev. Res., 23(1), Nov – Dec 2013; nᵒ 24, 116-120 ISSN 0976 – 044X International Journal of Pharmaceutical Sciences Review and Research Available online at www.globalresearchonline.net 116 Munmi Borkataky 1* , Bibhuti Bhusan Kakoty 2 , Lakhi Ram Saikia 3 1,3 Department of Life Sciences, Dibrugarh University, Dibrugarh, Assam, India. 2 Department of Pharmaceutical Sciences, Dibrugarh University, Dibrugarh, Assam, India. *Corresponding author’s E-mail: mbk139@gmail.com Accepted on: 21-08-2013; Finalized on: 31-10-2013. ABSTRACT Plants have been utilized as a source of nutrition and healthcare products since ancient times. A weed is a collective name given to plants are that grow and compete with the cultivated crops and are found to be resistant to most of the microbial diseases when compared to the cultivated crops. Ageratum conyzoides, Eupatorium odoratum and Mikania micrantha are members of Asteraceae, which is an exceedingly large and widespread family of some common well known weeds. Phytochemicals are secondary metabolites and are known to exert profound influence on various activities of plants. Methanolic extract of the plants revealed the presence of major phytochemicals in all of them.The antimicrobial potential of the plant extracts was evaluated against standard test strains and compared to the standard drug by the Activity Index (A.I.). It revealed that M. micrantha showed highest inhibition of B. cereus among the three plants. E.odoratum exhibited the highest antifungal activity followed by A. conyzoides. The antimicrobial potential of the three plants was compared in terms of the Proportion Index (P.I.). Although E. odoratumand M. micrantha exhibited to be equally potent in inhibiting the test strains, E. odoratum showed activity against both bacteria and fungi while M. micrantha showed only antibacterial activity. A. conyzoides exhibited a lower inhibitory potential but exhibited both antibacterial and antifungal activities. Keywords: Activity Index, Antimicrobial Activity, Asteraceae, Phytochemical Screening, Weeds. INTRODUCTION lants, since ancient times have been utilized as a source of nutrition and healthcare products. Plants are a reservoir of diverse kinds of bioactive chemical agents and have often been utilized either in the form of traditional preparations or as pure active principles. It is reasonable to make use of locally available plants, domesticated or wild, that could substitute the synthetic preparations.The healing powers of traditional herbal medications have been validated by various workers. The use of herbs as complementary and alternative medicine has increased dramatically in the last 20–25 years. 1 Moreover, emergence of multiple drug resistant strains of microorganisms due to indiscriminate use of antibiotics has generated a renewed interest in herbal medicines. 2 Weeds, commonly defined as a plants that grows out of place and are competitive, persistent and pernicious 3 , have been a part of civilization and many ancient documents mention about humans battling weeds in the crop fields. Traditional healers recognized their medicinal potential and utilized them for the treatment of human ailments. Weeds are also found to be resistant to most of the microbial diseases when compared to the cultivated crops. 4 The resistance of weeds towards the microbial diseases provoked many workers to explore the reasons for such potency. Antimicrobial potential of different types of weeds is being studied extensively all over the world. 5-11 The present study was conducted to know the major phytoconstituents of the plants and further analysis was conducted to explore the antibacterial and antifungal potentials of common Asteraceae weeds. Asteraceae or Compositae, commonly referred to as the aster, daisy, or sunflower family, is an exceedingly large and widespread family of Angiospermae. The members have a wide range of adaptation to suit the different ecological niche and can thrive well even in inhospitable areas. The plants of this family are mostly herbs, some are climbers but shurbs and trees are very rare.This family has a remarkable ecological and economic importance. 12 Some members of this family are in famous as important weeds. Three well known examples are- Ageratum conyzoides Linn., Eupatorium odoratum Linn., Mikania micrantha H. B & K. Ageratum conyzoides Linn. (Common name- Goat weed; Vernacular name- Gondhwabon) It is an annual herb, 30- 40 cm. high, stems erect, hairy-green or purple. Leaves opposite, broadly ovate, creanate, coarsely hairy on both sides, 3- nerved at the base. The inflorescence is a terminal corymb of many small heads; flowers violet or white. The juice from the fresh plant and the extract of the dried plant are used for the cure of allergic rhinitis and sinusitis, in aqueous solution for nasal instillation. The juice is also useful in post-partum uterine fragrant. A hair-wash consisting of a decoction of the fresh plant makes the hair fragrant, soft and dandruff-free. The plant extract is also known to prevent tetanus. 13 Eupatorium odoratum Linn. (Common name- Siam weed; Vernacular name- German habi). A scandent semi-woody annual plant with perennial root stock and pungent smell. Antimicrobial Activity and Phytochemical Screening of Some Common Weeds of Asteraceae Family P Research Article