ABSTRACT
A total of five compounds, namely lupeol (1), α-amyrin (2), stigmasterol (3), β-sitosterol (4) and 7,3′-dimethoxyluteolin (5) were isolated from a methanol extract of Albizia chinensis stem bark. The structures of the isolated compounds were established using nuclear magnetic resonance (NMR) spectroscopic studies, as well as using comparative thin layer chromatography (co-TLC) with standards. The methanol extract of the A. chinensis stem bark and its n-hexane-, carbon tetrachloride-, chloroform- and aqueous-soluble partitionates were evaluated for antioxidant activity with 1,1-diphenyl- 2-picrylhydrazyl (DPPH), Folin-Ciocalteu reagent and phosphomolybdenum total antioxidant assays, where butylated hydroxytoluene (BHT) and ascorbic acid were used as standards. The carbon tetrachloride-soluble fraction contained a moderate amount of phenolic compounds (60.76 ± 0.45 mg of GAE/g of extract) and it exhibited significant free radical-scavenging activity (IC50 10.21 ± 0.84 μg ml–1). A positive correlation was observed between the total phenolic content and the total antioxidant capacity of A. chinensis. The general toxicity was determined using a brine shrimp lethality bioassay, where the carbon tetrachloride (LC50 0.608 ± 0.19 μg ml–1) and hexane (LC50 0.785 ± 0.26 μg ml–1) soluble partitionates had considerable bioactive properties. The crude extract and its chloroform- and aqueous-soluble fractions displayed significant antimicrobial activity against eighteen microorganisms with inhibition zones ranging from 7.0 mm to 26.0 mm.
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