Potent inhibition of fatty acid synthase by parasitic loranthus [Taxillus chinensis (DC.) Danser] and its constituent avicularin

Abstract

The medicinal herb parasitic loranthus in a screen was found to inhibit fatty acid synthase (EC 2.3.1.85, FAS) and reduce body weight of rats in our previous study. Now we have determined the inhibitory characteristics and kinetic parameters of extracts of parasitic loranthus [Taxillus chinensis (DC.) Danser]. The parasitic loranthus extracts (PLE) inhibits FAS reversibly and irreversibly and with an IC₅₀ value of 0.48 μg/ml, appears to be the most potent inhibitor reported to date. PLE contains various potent inhibitors and may react with different sites on FAS. The irreversible inhibition exhibits a time-dependent biphasic process including a speedy fast-phase during the initial several minutes. The fast-phase inhibition seems to be caused by some potent but low-concentration component(s) in the extracts. In addition, we have found that avicularin existing in this herb can potently inhibit FAS. This glycosylated flavonoid and quercetin play an effective role in inhibiting FAS by parasitic loranthus.

Keywords::

• Fatty acid synthase
• inhibition
• kinetics
• parasitic loranthus (Taxillus chinensis)
• avicularin

Acknowledgements

This work is supported by Grant 30270324 of China National Science Foundation and the Procter & Gamble Company (Mason, OH, USA). We appreciate the assistance of Prof. Liangwei Zhong (Graduate University of Chinese Academy of Sciences, Beijing, China) in the completion of this manuscript.