Laccase-generated tetramethoxy azobismethylene quinone (TMAMQ) as a tool for antioxidant activity measurement

The potential of laccase-generated tetramethoxy azobismethylene quinone (TMAMQ) for measuring antioxidant activity of a wide range of structurally diverse molecules present in food and humans was investigated for the first time. All the tested antioxidants including simple phenolics, polyphenols and vitamins quenched TMAMQ. The antioxidant activity of phenolics and polyphenolics depended on the position and number of hydroxyl groups on the benzene ring. Equally interesting was the ability of amino acids like cysteine, tryptophan and methionine as well as peptides (glutathione) and proteins (albumin) to quench TMAMQ, demonstrating the great potential of TMAMQ for analysis of antioxidant activity of serum samples. Further, TMAMQ is promising is a more reliable tool for measuring antioxidant activity of amino acids when considering conflicting reports on antioxidant activity of some of the amino acids. The extracts from various food samples showed varying antioxidant activity with highest for spinach (4.36 mg methanol extract/mmol TMAMQ) followed by kiwi (13.95 mg methanol extract/mmol TMAMQ) and lettuce (40 mg methanol extract/mmol TMAMQ). The use of the laccase generated TMAMQ can be exploited for the development of laccase based biosensors for complex and coloured samples thereby facilitating online monitoring of antioxidants in food, cosmetic and health industries.