Heptaoxygenated xanthones as anti-austerity agents from Securidaca longepedunculata

In a course of our search for anticancer agent based on a novel anti-austerity strategy, we found that the CHCl3 extract of the roots of Securidaca longepedunculata (Polygalaceae), collected at Democratic Republic of Congo, killed PANC-1 human pancreatic cancer cells preferentially in nutrient-deprived medium (NDM). Phytochemical investigation on the CHCl3 extract led to the isolation of 28 compounds including five new polymethoxylated xanthones [1,6,8-trihydroxy-2,3,4,5-tetramethoxyxanthone (1), 1,6-dihydroxy-2,3,4,5,8-pentamethoxyxanthone (2), 8-hydroxy-1,4,5,6-tetramethoxy-2,3-methylenedioxyxanthone (3), 4,6,8-trihydroxy-1,2,3,5-tetramethoxyxanthone (4), 4,8-dihydroxy-1,2,3,5,6-pentamethoxyxanthone (5)] and a new benzyl benzoate [benzyl 3-hydroxy-2-methoxybenzoate (6)]. Among them, 1,6,8-trihydroxy-2,3,4,5-tetramethoxyxanthone (1) and 1,6-dihydroxy-2,3,4,5,8-pentamethoxyxanthone (2) displayed the potent preferential cytotoxicity with PC50 of 22.8 and 17.4 μM, respectively. They triggered apoptosis-like PANC-1 cell death in NDM with a glucose-sensitive mode.