New Phenylpropanoid-Substituted Flavan-3-ols from the Leaves of Castanopsis sclerophylla

In the course of a chemotaxonomical study of Chinese Castanopsis species, two previously unknown flavan-3-ols, named sclerophynins A and B, were isolated from the leaves of C. sclerophylla, together with five related known compounds. On the basis of spectroscopic analysis, the new compounds were characterized to be (4S,8R,9S)-4-(3,4-dihydroxyphenyl)-8-(3,4, 5-trihydroxyphenyl)-3,4,9,10-tetra-hydro-5,9-dihydroxy-2H,8H-benzo[1,2-b:3,4-b']dipyran-2one and (4S,7S,8R)-4,8-bis(3,4-dihydroxyphenyl)-3,4,6,7-tetrahydro-5-glucopyranosyloxy-7-hydroxy-2H,8H-benzo[1,2-b:5,4-b']dipyran-2-one, respectively. The genus Castanopsis belongs to the family Fagaceae and contains approximately 120 species. Over 50 species have been recorded in East Asia, many of which are important as ornamental trees and for use as construction materials. Seeds of some species are edible and the leaves and bark have been used medicinally. Despite the large number of species, however, few chemotaxonomical studies have been performed. Previously, characteristic triterpene hexahydroxydiphenoyl (HHDP) esters were isolated from the leaves of C. cuspidata var. sieboldii and C. hystrix. The triterpene HHDP esters have been found only in these Castanopsis species and have been shown to have chemotaxonomical significance. Thus, we began a phytochemical study of the phenolic constituents of the Chinese Castanopsis species. C. sclerophylla is an evergreen tree distributed throughout Southern China. The leaves and seeds are rich in tannins and are used for the treatment of hemorrhage, chronic ulcers and diarrhea. Our preliminary analysis, using HPLC and TLC, indicated that the leaves do not contain triterpene HHDP esters. It did, however, reveal the presence of unusual flavan-3-ols. This paper presents the structure determination of two previously unknown compounds.