Thunberol, a new sterol from the Chinese brown alga Sargassum thunbergii

Abstract

A new sterol, named thunberol (1), along with four known analogs, 24-ethylcholesta-4,24(28)-dien-3-one (2), stigmasta-5,28-dien-3β-ol (3), cholesta-5,14-dien-3β-ol (4), and cholesta-5,23-dien-3β,25-diol (5), were isolated from the brown alga Sargassum thunbergii collected from China Sea. The structures of these metabolites were elucidated on the basis of detailed spectroscopic analysis and by comparison with the literature data. Thunberol (1) exhibited significant inhibitory activity against protein tyrosine phosphatase 1B, a potential drug target for the treatment of Type-II diabetes and obesity, with an IC₅₀ value of 2.24 μg/ml.

Keywords::

• brown alga
• Sargassum thunbergii
• sterol
• oxygenated steroid

Acknowledgments

This research work was financially supported by the Natural Science Foundation of China (Nos 41306130, 21072204, 21021063, and 81273430), the National Marine “863” Project (Nos 2011AA-09070102 and 2013AA092902), and China Postdoctoral Foundation Grant (No. 2012M520956). The authors thank Dr Wan-Dong Chen of Nanji Island National Reserve Administration for identification of the specimen.