beta-Carbolines that accumulate in human tissues may serve a protective role against oxidative stress

beta-Carbolines are tricyclic nitrogen heterocycles formed in plants and an imals as Maillard reaction products between amino acids and reducing sugars or aldehydes. They are being detected increasingly in human tissues, and t heir physiological roles need to be understood. Two beta-carboline carboxyl ates have been reported to accumulate in the human eye lens. We report here on the identification of another beta-carboline, namely 1-methyl-1-vinyl - 2,3,4 trihydro-beta-caboline-3-carboxylic acid, in the lenses of some catar act patients from India. Analysis of these three lenticular beta-carbolines using photodynamic and antioxidant assays shows all of them to be inert as sensitizers and effective as antioxidants; they quench singlet oxygen, sup eroxide and hydroxyl radicals and inhibit the oxidative formation of higher molecular weight aggregates of the test protein, eye lens crystallin. Such antioxidative ability of beta-carbolines is of particular relevance to the lens, which faces continual photic and oxidative stress. The beta-carbolin e diacid TV is also seen to display an unexpected ability of inhibiting the thermal coagulation of gamma-crystallin and the dithiothreitol-induced pre cipitation of insulin. These results offer experimental support to earlier suggestions that one of the roles that the beta-carbolines have is to offer protection against oxidative stress to the human tissues where they accumu late.