Two new coumarins and a new xanthone from the leaves of Rhizophora mucronata

Abstract Two new coumarins ( 1 , 2 ) and a new xanthone ( 3 ), together with 14 known compounds—eight coumarins ( 4 , 5 , 9 , 10 , 12 – 15 ), three xanthones ( 11 , 16 , 17 ), a benzoic acid ( 6 ) and two flavonones ( 7 , 8 )—were isolated from the leaves of Rhizophora mucronata . The structures of the compounds were elucidated by spectroscopic (IR, MS, and NMR) analyses. The isolated compounds were tested for cytotoxicity against human cancer cell lines HL-60 and HeLa. Among these compounds, only compound 16 inhibited the growth of both HeLa (IC 50  = 4.8 μM) and HL-60 (IC 50  = 1.0 μM) cells. Compounds 4 , 7 , 10 , and 12 exhibited moderate activity against HeLa cells (IC 50  = 3.8–8.3 μM). Compounds 5 , 9 , 11 , and 17 showed moderate activity against HL-60 cells (IC 50  = 2.2–6.3 μM). Higher selectivity against HL-60 cell lines was observed for compounds 5 , 9 , 11 , and 16 with SI values (NIH 3T3/HL-60) of 8.6, 19.2, 9.4, and 10.2, respectively.