Chem. Pharm. Bull. 54(10) 1433—1436 (2006)

consisting of about 47 species distributed in south-eastern Asia and the Pacific, and some species are cultivated throughout the tropics. A number of Artocarpus species, including A. rigidus BLUME subsp. rigidus are found wild in the southern part of Thailand. No phytochemical investigation of this plant species has been reported to date. It should be noted that this plant species is different from A. rigida, the latter of which has been extensively investigated. As part of an ongoing project on bioactive compounds from Thai plants for the treatment of tropical diseases, the plant species was investigated and it was found that the CHCl3 and MeOH extracts exhibited antiplasmodial and antimycobacterial activities. Both crude extracts also showed cytotoxic activity against human epidermoid carcinoma of the nasopharynx (KB), human breast cancer (BC), and human small cell lung cancer (NCI-H187) cells. The present report deals with the isolation and antiplasmodial, antimycobacterial, and cytotoxic activities of the isolated new compounds 1 and 2, and the known compounds 3—6. Investigation of the chemical constituents of the root bark of A. rigidus subsp. rigidus resulted in the isolation of six compounds. These included two new phenolics with modified skeletons, the flavonoid 7-demethylartonol E (1) and the chromone artorigidusin (2), together with four, known, structurally modified phenolics, the xanthone artonol B (3), the flavonoid artonin F (4), the flavonoid cycloartobiloxanthone (5), and the xanthone artoindonesianin C (6). Compounds 3 and 4 were identified as artonol B and artonin F isolated previously from A. communis on the basis of spectroscopic (Hand C-NMR spectral) comparisons. On the same basis, compounds 5 and 6 were identified as cycloartobiloxanthone and artoindonesianin C isolated from A. nobilis and A. teysmanii respectively. Compound 1 was obtained as a pale brownish yellow powder, mp 224—226 °C. The IR spectrum showed absorptions for the hydroxyl (3535, 3434 cm ) and conjugated keto (1662 cm ) groups. The HR-FAB-MS (positive ion mode) gave an [M H] ion at m/z 435.1446, corresponding to a molecular formula of C25H22O7. The H-NMR spectrum of 1 (Table 1) revealed two doublets (J 1.9 Hz) at d 6.24 and 6.56 corresponding, respectively, to the characteristic H-6 and H-8 signals of a flavonoid. The 5,7-dihydroxyl substituted pattern was confirmed by HMBC correlations as shown October 2006 1433 Chem. Pharm. Bull. 54(10) 1433—1436 (2006)