Triterpenoids from Gutenbergia nigritana(Benth).Oliv and Hiern
Gutenbergia nigritana (Benth).Oliv and Hein (Asteraceae) is a Nigerian ethnomedicinal plant which has long being used medicinally in traditional systems of medicine.The plant has diverse ethnomedicinal uses which include: The Plant is used in the Ijaw area of Niger Delta region of Nigeria to treat Malaria,convulsion,diarrhea and as a remedy for skin infection. The antibacterial study on dichloromethane extract and chromatographic fractions:dichloromethane soluble part(DC1),ethyl acetate soluble part(E1) and N-butanol soluble portions of methanolic extract were investigated using agar diffusion assay method by measuring the zone of inhibition against clinical isolates: Bacillus subtillis,Escherichia coli,Staphylococcus aureus and Pseudomonas aeruginosa.Extensive Chromatographic separation and preparative TLC were employed in the isolation steps. Column chromatograpy of the dichloromethane extract, gel filteration on sephadex and preparative TLC led to the isolation of two triterpenoids: Lupenol(1) and Lupenol acetate(2). The structures were elucidated
by NMR spectroscopy and compared with literature. The dichloromethane extract exhibited antibacterial activity against all the test microorganisms with zones of inhibition ranging between 12-26mm. The chromatographic fraction (Fr-6) exhibited activity against E.coli,Ps.aeruginosa and S.aureus but in-active against B.subtilis, while the methanol soluble portions:
dichloromethane and ethyl acetate showed weak activity while the n-butanol portion was in active. Dichloromethane extract of Gutenbergia nigritana leaves exhibited anti-bacterial activity, though the compounds isolated did not show activity, it is likely that the activity might reside in other components present in the dichloromethane extract.
Key words: Lupenol, Lupenol acetate,antibacterial activity.