Diarylheptanoids, new phytoestrogens from the rhizomes of Curcuma comosa: Isolation, chemical modification and estrogenic activity evaluation

Five new naturally occurring and nine known diarylheptanoids were isolated. Some of them exhibited higher estrogenic activity than the phytoestrogen genistein. Three new diarylheptanoids, a 1:2 mixture of (3 S)- and (3 R)-1-(4-methoxyphenyl)-7-phenyl-(6 E)-6-hepten-3-ol ( 13a and 13b) and 1-(4-hydroxyphenyl)-7-phenyl-(6 E)-6-hepten-3-one ( 15), together with two synthetically known diarylheptanoids 1,7-diphenyl-(1 E,3 E,5 E)-1,3,5-triene ( 9) and 1-(4-hydroxyphenyl)-7-phenyl-(4 E,6 E)-4,6-heptadien-3-one ( 16), and nine known diarylheptanoids, 2, 8, 10– 12, 14, a 3:1 mixture of 17a and 17b, and 18, were isolated from the rhizomes of Curcuma comosa Roxb. The absolute stereochemistry of the isolated compounds has also been determined using the modified Mosher’s method. The isolated compounds and the chemically modified analogues were evaluated for their estrogenic-like transcriptional activity using RT-PCR in HeLa cell line. Some of the isolated diarylheptanoids and their modified analogues exhibited estrogenic activity comparable to or higher than that of the phytoestrogen genistein. Based on the transcriptional activation of both estrogenic targets, Bcl-xL and ERβ gene expression, the structural features for a diarylheptanoid to exhibit high estrogenic activity are the presence of an olefinic function conjugated with the aromatic ring at the 7-position, a keto group at the 3-position, and a phenolic hydroxyl group at the p-position of the aromatic ring attached to the 1-position of the heptyl chain.