Isolation and Characterisation of Bioactive Principles from Sapwood of Pterocarpus santalinoides

Abstract

Pterocarpus santalinoides is a medicinal plant widely employed in traditional Nigerian medicine for managing diverse health conditions. The present study focuses on the isolation and characterisation of biologically active compounds from the sapwood of Pterocarpus santalinoides.

. Sequential extraction was carried out using n-hexane, ethyl acetate, and methanol, followed by purification of the ethyl acetate extract through column chromatography. Thin Layer Chromatography (TLC) was employed for fraction monitoring, while the structures of isolated compounds were elucidated using ¹H, ¹³C, and 2D NMR techniques, including HMBC, HSQC, and COSY, in comparison with existing literature. The identified compounds included lupeol, a mixture of β-sitosterol and stigmasterol, a 1,2-diacylglycerolipid containing polyunsaturated ω-6 and ω-3 acyl chains, a diacylglycerol with one polyunsaturated and two saturated/monounsaturated chains, and oleanolic acid. Crude extracts of Pterocarpus santalinoides, including ethyl acetate, methanol, and hexane, exhibited significant antimicrobial activity against both Gram-positive and Gram-negative microorganisms. Notably, fraction EPs14 demonstrated superior efficacy, with inhibition zones of 23 mm to 27 mm against various fungi and bacteria. EPs26 and EPs36 showed the highest inhibition zones of 29 mm and 30 mm, respectively, against Phaeolus schweinitzii and Coniophora puteana. Minimum inhibitory concentrations (MIC) for these fractions were as low as 6.25 µg/mL. These findings support the traditional use of P. santalinoides in the treatment of diarrhoea, placentitis, skin infections, and gastrointestinal disorders, marking the first report of these bioactive compounds from the plant’s sapwood.