title: Potent microbial and tyrosinase inhibitors from stem bark of Bauhinia rufescens (Fabaceae).
abstract: The stem bark extracts of Bauhinia rufescens Lam. (Fabaceae) yielded 6-methoxy-7-methyl-8-hydroxydibenz[b,f]oxepin, alpha-amyrin acetate, beta-sitosterol 3-O-beta-D-xylopyranoside, 4-(2'-Hydroxyphenethyl)-5-methoxy-2-methylphenol, menisdaurin and sequoyitol. Their structures were determined using spectroscopic methods and comparisons with the literature data. For the antimicrobial assay Gram-positive and Gram-negative bacterial and fungal strains were tested, while the tyrosinase inhibition assay utilized L-DOPA as a substrate for the tyrosinase enzyme. 6-Methoxy-7-methyl-8-hydroxydibenz[b,f]oxepin, a-amyrin acetate, beta-sitosterol 3-O-D-xylopyranoside, menisdaurin and sequoyitol showed weak to moderate activities with minimum inhibition concentration (MIC) values in the range of 112.5-900 microg/mL against all bacterial strains, while the MIC values for the fungal strains were in the range of 28.1-450 microg/mL. In the tyrosinase inhibition assay, a-amyrin acetate was found to be moderately active against tyrosinase with an inhibition of 62% at 0.1 mg/mL. This activity was lower than that of the positive control, kojic acid (85%).
authors.affiliation: Department of Chemistry, Faculty of Science, Universiti Teknologi Malaysia, 81310 Skudai, Johor Bahru, Malaysia.
authors.forename: Aminu
authors.initials: A
authors.lastname: Muhammad
authors.affiliation: Department of Chemistry, Faculty of Science, Universiti Teknologi Malaysia, 81310 Skudai, Johor Bahru, Malaysia.
authors.forename: Hasnah Mohd
authors.initials: HM
authors.lastname: Sirat
mesh_terms: D000900:Anti-Bacterial Agents / Q000737:chemistry / Q000302:isolation & purification*; D036481:Bauhinia / Q000737:chemistry*; D006027:Glycosides / Q000302:isolation & purification; D007294:Inositol / Q000031:analogs & derivatives / Q000302:isolation & purification; D008826:Microbial Sensitivity Tests; D014442:Monophenol Monooxygenase / Q000037:antagonists & inhibitors*; D009828:Oleanolic Acid / Q000031:analogs & derivatives / Q000302:isolation & purification; D010082:Oxepins / Q000302:isolation & purification; D024301:Plant Bark / Q000737:chemistry; D018547:Plant Stems / Q000737:chemistry; D010946:Plants, Medicinal / Q000737:chemistry; D013267:Stilbenes / Q000737:chemistry / Q000302:isolation & purification*; D000081014:Dihydrostilbenoids
chemical_list: D000900:Anti-Bacterial Agents; D006027:Glycosides; D007294:Inositol; D014442:Monophenol Monooxygenase; D009828:Oleanolic Acid; D010082:Oxepins; D013267:Stilbenes; C572459:5-O-methyl-myo-inositol; C504636:menisdaurin; C038546:1,2-dihydrostilbene; D000081014:Dihydrostilbenoids; C036380:beta-amyrin