Evaluation of Antimicrobial (Antibacterial and Antifungal) potential  of root extracts of Spilanthes acmella Murr. – An Important Medicinal Plant

Plants produce many secondary metabolites which constitute an important source of antimicrobial, anticancer and pharmaceutical activities. Plant extracts which inhibit the pathogenic microorganisms have potential use as therapeutic drugs. Spilanthes acmella. (Family : Asteraceae) is an important medicinal plant with major chemical compound spilanthol which is having many bioactive properties. The present study has been under taken to evaluate the antimicrobial potential of  root extract of S.acmella. In the present study, the methanolic extract of roots of S.acmella was tested for its antibacterial and antifungal activity by Agar cup bioassay method.. The antibacterial activity of root extract of S.acmella was studied against gram positive bacteria Bacillus subtilis, Staphylococcus aureus and gram negative bacteria Escherichia coli, Pseudomonas aeruginosa. The various concentrations of methanolic root extract (500, 1000, 1500, 2000 µg ) were tested and high activity was observed at 2000 µg. Among the test organisms, Pseudomonas aeruginosa showed highest zone of inhibition (3.3cm) followed by E.coli (2.8cm). Lesser activity was seen against Bacillus subtilis (2.6cm) and Staphylococcus aureus (2.1 cm). The antifungal activity of root extract of S.acmella was tested against five different fungal species i.e. Macrophomina phaseolina, Rhizoctonia solani, Fusarium oxysporum, Alternaria alternata and Colletotrichum capsicii. The various concentrations of methanolic root extract (500, 1000, 1500, 2000 µg) were tested and maximum activity was observed at 2000 µg. All the five organisms were inhibited by the test solution with varying sensitivity. Among all, high inhibition zones were observed in Fusarium oxysporum (2.8 cm) followed by Colletotrichum capsicii (2.5cm), Rhizoctonia solani (2.2cm.). The Alternaria alternata and Macrophomina phaseolina showed low inhibition zones of 2.0 cm and 1.8 cm respectively.