Polyanthumin, a novel cyclobutane chalcone trimmer from Memecylon polyanthum

Abstract

A novel unusual trimmer chalcone, polyanthumin (1), together with five known compounds myricetin 3-O-(3″-O-galloyl)-α-l-rhamnopyranoside (2), sulfuretin (3), fustin (4), gallic acid (5), and ethyl gallate (6), was isolated from the dry stems of Memecylon polyanthum H.L. Li. Among them, compound 1 is a new chalcone trimmer with a novel cyclobutane skeleton in nature. Compounds 3 and 4 are flavonoids carrying a single 7-OH in A ring, which provided the first example of these class flavonoids from the family Melastomataceae. In addition, the antitumor activities for 2–4 were reported for the first time in this study. The antitumor effects of the isolated compounds 1–6in vitro were assayed by the SRB method using human cancer K562 cells, with the inhibition rates ranging from 39.4% to 54.5% at 100 μg/ml. The IC₅₀ values of compounds 1 and 3 for the inhibition of K562 cell proliferation were determined to be 45.4 and 30.5 μg/ml, respectively. To the best of our knowledge, compound 1 was the second sample as chalcone trimer. In addition, the antitumor activities for 2–4 were reported for the first time in this study.

Keywords::

• cyclobutane chalcone trimmer
• structure determination
• antitumor activity
• Memecylon polyanthum
• Melastomataceae

Notes

Dedicated to Professor Xin-Sheng Yao on the occasion of his 80th birthday.