Antimicrobial evaluation of Rhizome Extracts and Chemical Characterization of the hexane Extracts of Costuslucanusianus J. Braun&Shum

Abstract

Micro-organisms resistance to antimicrobial agents has prompted a quest for novel potent antimicrobial agents which are particularly derived from natural sources. Costuslucanusianus(J.Braun&Shum) is a plant generally utilized in traditional medicine for the treatment of innumerable infectious diseases including venereal diseases. However, there is limited information on the antimicrobial potency of its rhizome crude extracts and chemical compositions. This study is aimed at determining the chemical composition and antimicrobial potency of C. lucanusianus rhizome organ. The antimicrobial potency of various concentrations (12.5-100 μg/mL) of the ethyl acetate, hexane and methanol extracts of the rhizome was evaluated against six bacterial and four fungal strains using the Agar well diffusion techniques. Minimum inhibition concentration (MICs) of the most potent extracts was determined using Agar Microdilution method. The most potent plant extract was further subjected to chromatographic separation and then structural elucidation using NMR spectroscopy. The extracts displayed varying antimicrobial activity against the micro-organisms, and MICs for the most potent extracts ranged from 3.125 µg /ml to 6.25 µg/ml. Chromatographic studies of the hexane extract led to the isolation of a compound Z, a mixture of isonuatigenin and diosgenin whose structures were established with NMR and comparison with literature data. The in vitro antimicrobial activity displayed by the crude extracts from C. lucanusianus rhizomes highlights its potential for the treatment of infectious diseases in ethnomedicine.