Anti-malarial activity of some xanthones isolated from the roots of Andrographis paniculata

Abstract

Four xanthones were isolated from the roots of Andrographis paniculata using a combination of column and thin-layer chromatographic methods. They were characterized as (i) 1,8-di-hydroxy-3,7-dimethoxy-xanthone, (ii) 4,8-dihydroxy-2,7-dimethoxy-xanthone, (iii)1,2-dihydroxy-6,8-dimethoxy-xanthone and (iv) 3,7,8-trimethoxy-1-hydroxy xanthone by IR, MS and NMR spectroscopic methods. In vitro study revealed that compound 1,2-dihydroxy-6,8-dimethoxy-xanthone possessed substantial anti-plasmodial activity against Plasmodium falciparum with its IC₅₀ value of 4 μg ml⁻¹. Xanthones bearing hydroxyl group at 2 position demonstrated most potent activity while xanthones with hydroxyl group at 1,4 or 8 position possessed very low activity. In vivo anti-malarial sensitivity test of this compound on Swiss Albino mice with Plasmodium berghei infection using Peters' 4-0day test gave substantial reduction (62%) in parasitaemia after treating the mice with 30 mg kg⁻¹ dose. In vitro cytotoxicity against mammalian cells revealed that 1,2-dihydroxy-6,8-dimethoxy-xanthone is non-cytotoxic with its IC50 > 32 μg ml⁻¹.