Chem. Pharm. Bull. 54(5) 745—747 (2006)

belonging to the family Guttiferae. Some species of Cratoxylum have been used as traditional medicine. Previous chemical investigations of this genus have revealed the presence of xanthones, triterpenoids and flavonoids. In the course of our ongoing search for bioactive compounds from natural sources, hexane extract of the roots of C. cochinchinense exhibited cytotoxic activity against the NCI-H187 cell line and antimalarial activity against Plasmodium falciparum. Bioassay-guided investigation of this extract resulted in the identification of a new xanthone, 5-O-methylcelebixanthone (1), together with six known compounds (2—7). In this paper we report the isolation and structural elucidation of the new compound (1). The biological evaluation of all compounds is also reported. In addition, the full assignment of Hand CNMR spectral data of 2 (Table 1) is also reported herein for the first time. Compound 1 was deduced to have a formula of C20H20O6 by HR-EI-MS, which showed a molecular ion peak at m/z 356.1229 (Calcd 356.1259). The IR spectrum showed absorption bands at 3357 cm 1 for hydroxyl group and 1646 cm 1 for conjugated carbonyl functionality which was also confirmed by the C-NMR spectrum (Table 1) at d 183.6 (C-9). This carbonyl moiety formed a hydrogen bond with a hydroxyl group, as evidenced by a proton signal at d 13.10 (1-OH). The H-NMR (Table 1) and COSY spectral data revealed two methoxyl groups at d 4.10 (3H, s) and 3.82 (3H, s), one prenyl unit observed at d 5.21 (1H, m, H-2 ), 4.04 (2H, d, J 6.6 Hz, H-1 ), 1.85 (3H, s, H-5 ), and 1.69 (3H, d, J 1.5 Hz, H-4 ) and a 1,2,3-trisubstituted benzene ring at d 7.53 (1H, t, J 8.4 Hz, H-3), 6.91 (1H, dd, J 8.4, 0.9 Hz, H-4), and 6.78 (1H, dd, J 8.4, 0.9 Hz, H-2). In the May 2006 745