In this study, five compounds, lupeol (1), epilupeol (2), β-sitosterol (3), stigmasterol (4) and p-methoxybenzaldehyde (5) were isolated from the petroleum ether and dichloromethane fractions of a methanolic extract of the stem bark of Delonix regia. Antimicrobial screening of the different extracts (15 μg mm-2) was conducted by the disc diffusion method. The zones of inhibition demonstrated by the petroleum ether, carbon tetrachloride and dichloromethane fractions ranged from 9-14 mm, 11-13 mm and 9-20 mm, respectively, compared to kanamycin standard with the zone of inhibition of 20-25 mm. In brine shrimp lethality bioassay, the carbon tetrachloride soluble materials demonstrated the highest toxicity with LC50 of 0.83 μg mL-1, while petroleum ether and dichloromethane soluble partitionates of the methanolic extract revealed LC50 of 14.94 and 3.29 μg mL-1, respectively, in comparison with standard vincristine sulphate with LC50 of 0.812 μg mL-1. This is the first report on compounds separation from D. regia, their antimicrobial activity and cytotoxicity.
