RESEARCH ARTICLE
Multifunctional Antioxidant Activities of Alkyl Gallates
Isao Kubo*, Noriyoshi Masuoka, Tae Joung Ha, Kuniyoshi Shimizu, Ken-ichi Nihei
Article Information
Identifiers and Pagination:
Year: 2010Volume: 3
First Page: 1
Last Page: 11
Publisher Id: TOBCJ-3-1
DOI: 10.2174/1874847301003010001
Article History:
Received Date: 14/4/2009Revision Received Date: 13/5/2009
Acceptance Date: 20/5/2009
Electronic publication date: 27/1/2010
Collection year: 2010
open-access license: This is an open access article licensed under the terms of the Creative Commons Attribution Non-Commercial License (http://creativecommons.org/licenses/by-nc/3.0/) which permits unrestricted, non-commercial use, distribution and reproduction in any medium, provided the work is properly cited.
Abstract
A series (C1 to C16) of alkyl gallates was tested for their antioxidant activity for food protection and human health. One molecule of alkyl gallate, regardless of alkyl chain length, scavenges six molecules of 1,1-diphenyl-2-picrylhydrazyl (DPPH). Alkyl gallates inhibited the linoleic acid peroxidation catalyzed by soybean lipoxygenase-1 (EC 1.13.11.12, Type 1) without being oxidized. The progress curves for enzyme reactions were recorded by both spectrophotometric and polarographic methods and the inhibitory activity was a parabolic function of their lipophilicity (log P) and maximized with alkyl chain length between C12 and C16. Tetradecanyl (C14) gallate exhibited the most potent inhibition with an IC50 of 0.06 µM. The inhibition kinetics of dodecyl gallate (C12) revealed competitive and slow-binding inhibition. Alkyl gallates chelate transition metal ions and this chelation ability should be of considerable advantage as antioxidants. Additionally, gallic acid was found to inhibit superoxide anion generated by xanthine oxidase (EC 1.1.3.22) but did not inhibit enzymatically catalyzed uric acid formation.