ABSTRACTMedicinalplants contain bioactive compounds or plant metabolites that serve an importanttherapeutic role in curing and healing some human maladies such as microbialdiseases. Some of these bioactive compounds exhibit especially goodantimicrobial effects upon pathogenic agents that have become a major publichealth problem around the world causing death and upsurge of resistance todrugs commonly used. Plantmetabolites such as flavonoids have been reported to display antimicrobialproperties against some microbe strains whereas genus the Tephrosia is known to be rich in flavonoids. In the search toisolate from medicinal plants the compounds that exhibit antimicrobial effects,Tephrosia hildebrandtii aerial partwas phytochemically analyzed.
Thephytochemical investigation on this plant material led to the isolation of fiveflavones derivatives, a sterol, a triterpene and a carotenoid. Five of theisolated compounds were new and their structures were established using acombination of techniques including NMR, UV and MS.Boththe MeOH/CH2Cl2 (1:1 v/v) crude extract and the isolatedcompounds were tested for antimicrobial activity against Escherichia coli (gram negative bacterium), Bacillus cereus (gram positive bacterium) and Candida albicans (fungus).
The crude extract, compound (90) and compound (91) showed significant activity against Escherichia coli with ZI values of 15, 18 and 15 mm respectivelyand MIC values of 2.50, 0.25 and 0.
50 mg/mL respectively. The crude extract andcompound (90) also exhibited goodactivity against Candida albicanswith ZI values of 18 and 21 mm respectively and MIC values of 2.50 and 0.25mg/mL respectively while compounds (94),(95) and (96) showed a moderate activity with ZI values of 13, 14 and 14 mmrespectively and MIC values of 0.50, 0.50 and 0.50 mg/mL respectively.
Compound(90) and the mixture of compounds (92,93) showed good activities against Bacilluscereus with ZI values of 14 and 17 mm respectively and MIC values of 0.50and 0.25 mg/mL respectively while the crude extract and compound (91) were moderately active with ZIvalues of 11 and 11 mm respectively and MIC values of 5.
00 and 0.50 mg/mLrespectively.Pyrazolineand guanidine derivatives of compound (94)have been prepared on the treatment with guanidine hydrochloride and hydrazinehydrate in presence of alkali respectively. structures