A new benzophenone, and the antiplasmodial activities of the constituents of Securidaca longipedunculata fresen (Polygalaceae)

Abstract

Extracts from Securidaca longipedunculata showed antiplasmodial activities against reference clones and clinical isolates using SYBR Green I method. A new benzophenone, 2,3,4,5-tetramethoxybenzophenone (1) was isolated and characterized along with seven known compounds: 4-hydroxy-2,3-dimethoxybenzophenone (2); 3-hydroxy-5-methoxybiphenyl (3), methyl-2-hydroxy-6-methoxybenzoate (4), benzyl-2-hydroxy-6-methoxybenzoate (5), 2-hydroxy-6-methoxybenzoic acid (6), 2,4,5-trimethoxybenzophenone (7) and 2-methoxy-3,4-methylenedioxybenzophenone (8). Compounds 1 and 2 showed ex vivo antiplasmodial activities (IC₅₀ 28.8 μM and 18.6 μM, respectively); while 5 and 8 showed in vivo activities (IC₅₀ 19.7 μM and 14.5 μM, respectively) against D6 strain. In a cytotoxicity assay, all the extracts (with an exception of the MeOH extract of the leaves) and pure compounds were not toxic to the normal LO2 and BEAS cell-lines, while the methanol roots extract (IC₅₀ 66.4 µg/mL against A549, and 77.4 µg/mL against HepG2), compounds 6 (IC₅₀ 22.2 µM against A549) and 7 (IC₅₀ 45.2 µM against HepG2) were weakly active against cancerous cell-lines.

Keywords: 2,3,4,5-tetramthoxybenzophenone; Antiplasmodial; Securidaca longipedunculata; benzophenone; cytotoxicity; ex vivo.