Stigmasterol as Antimicrobial Agent from Root Extracts of Cola millenii

Abstract

Cola millenii is a plant found in the North central Nigeria used in the treatment of many diseases like dysenterie, gonorrhoea, skin infection, typhoid fever etc. Phytochemical and antimicrobial studies were carried out on the root part of the plant. The phytochemical screening was carried out using standard procedures and the antimicrobial activity was tested against some pathogens using the tube dilution and agar diffusion method outlined by the National Committee for clinical laboratory studies (NCCLS). The result of the phytochemical screening of n-hexane, ethyl acetate and methanol extracts revealed the presence of cardiac glycoside, saponins, steroids and triterpenes, flavonoids, Tannins and Alkaloids. The results of the antimicrobial activity as indicated by the zone of inhibition of growth of microorganisms ranged from 16mm to 20mm for n-hexane extract, 24mm to 31mm for ethyl acetate extract and 20mm to 27mm for methanol extract. The MIC result for the n-hexane, ethyl acetate and methanol extracts ranged from 7.5mg/ml to 15mg/ml while the MBC result for the extracts ranged from 15mg/ml to 60mg/ml. Extensive chromatographic separation of the ethyl acetate extract (being the most active of all the extracts) led to the isolation of a compound considered to be stigmasterol by spectroscopy. The structure of the compound was established by spectral analysis including 1D and 2D NMR. The antimicrobial activity of the isolated compound as indicated by the zone of inhibition ranged from 26mm to 35mm on staphylococcus aureus, streptococcus pyogenes, E.coli, shigelladysenterie and klebseliapnuemoniea. The antimicrobial results as indicated by the zone of inhibition of the extracts and the isolated substance showed Cola millenii had a fair broad spectrum of activity. The medicinal use of the plant was therefore justified.