Antifungal and antileishmanial activities of fractions and isolated isoflavanquinones from the roots of Abrus precatorius

Neglected tropical diseases hinder social and economic growth in many tropical areas. We report leishmanicidal activities of isoflavanquinones and antifungal potentials of fractions from methanol root extract of Abrus precatorius. Agar dilution method was used to determine antifungal properties while 96-well dilution protocol was adopted for antileishmanial activities. Ethyl acetate fraction of A. precatorius root extract showed moderate activity against M. canis and F. solani with percentage inhibition of 42.5% and 55.0% respectively while other fractions were inactive. Crude extract, n-hexane, and ethyl acetate fractions demonstrated potent antileishmanial activities with IC₅₀ values of 22.20 ± 0.540 μg/mL, 19.35 ± 0.670 μg/mL, and 6.32 ± 0.001 μg/mL respectively, against L. major. The ethyl acetate fraction, which was the most active fraction, was subjected to successive column chromatography followed by preparative recycling HPLC in order to isolate the active constituents. Structures were established by HR-ESIMS, 1D and 2D NMR (1H, 13C, COSY, NOESY, HMBC, HSQC) spectroscopy. Two compounds were obtained and identified as isoflavanquinones: abruquinone A (1) and abruquinone B (2). Compounds 1 and 2 demonstrated significant (p < 0.05) antileishmanial activity against L. major (IC₅₀ 6.35 ± 0.005 μg/mL and 6.32 ± 0.008 μg/mL respectively) and L. tropica (IC₅₀ 6.29 ± 0.015 μg/mL and 6.31 ± 0.005 μg/mL, respectively). This appears to be the first report of antileishmanial activity of compounds 1 and 2 from the genus Abrus against cutaneous leishmaniasis and validates the use of A. precatorius in treating dermatology diseases.