Abstract: 1,2,3,4-Tetrahydro-β-carboline derivatives
(THβCs) are formed through Pictet-Spengler chemical
condensation between tryptophan and aldehydes during food production, storage
and processing. In the present study, in order to identify the antioxidants in
aged garlic extract (AGE), we fractionated it and identified four
THβCs;
1-methyl-1,2,3,4-tetrahydro-β-carboline-3-carboxylic
acids (MTCC) and
1-methyl-1,2,3,4-tetrahydro-β-carboline-1,3-dicarboxylic
acid (MTCdiC) in both diastereoisomers using liquid chromatography mass
spectrometry (LC-MS). Interestingly, these compounds were not detected in raw
garlic, but the contents increased during the natural aging process of garlic.
In in vitro assay systems, all of these compounds have shown strong
hydrogen peroxide scavenging activities. (1S, 3S)-MTCdiC was found to be
stronger than the common antioxidant, ascorbic acid. MTCC and MTCdiC inhibited
AAPH-induced lipid peroxidation. Both MTCdiCs also inhibited LPS-induced
nitrite production from murine macrophages at 10–100 μM.
Our data suggest that these compounds are potent antioxidants in AGE, and thus
may be useful for prevention of disorders associated with oxidative stress.
