Crystal structure of 1,5,8-trihydroxyl-3-methoxy xanthone from Swertia chirayita

In order to study the relationship between biological and pharmacological activities with their structures, a series of tri-, tetra-oxygenated xanthones including 1-hydroxyl- 2,3,4,7-tetramethoxy xanthone 1, 1-hydroxyl- 2,3,4,5-tetramethoxyl xanthone 2, 1-hydroxyl- 3,5dimethoxy xanthone 3, 1,8-dihydroxyl-3,5-dimethoxyl xanthone 4, 1,5,8-trihydroxyl-3-methoxy xanthone 5 has been isolated from Swertia chirayita. Their structures were established on the basis of spectral and chemical evidence. The crystal structure of 5 was also investigated by single crystal X-ray diffraction analysis. It crystallizes in the triclinic system, space group P (1) over bar, with a = 7.1540( 10) angstrom, b = 7.520( 2) angstrom, c = 10.671( 2) angstrom, V = 562.7( 2) angstrom(3), alpha = 86.50( 3)., = 80.06( 3)degrees, beta = 85.00(3)degrees, Z = 2, D-c = 1.618 g m(-3), R-int = 0.0230, wR(F-2) = 0.1028, F(000) = 284. The molecular structure is nearly plane and four substituents are much closer to the plane of the molecule. Compound 5 also shows three intermolecular hydrogen bonds. A recent study shows that phenolic hydroxyls in xanthones are the main active groups capable of scavenging (OH)-O-center dot and O-2(center dot).