Occurrence of 1,2,3,4-tetrahydro-β-carboline-3-carboxylic acid and 1-methyl-1,2,3,4-tetrahydro-β-carboline-3-carboxylic acid in fruit juices, purees, and jams

1,2,3,4-Tetahydro-beta-carboline-3-carboxylic acid (THCA) and 1-methyl-1,2,3,4-tetrahydro-beta-carboline-3-carboxylic acid (MTCA) as two diastereoisomers (1S,3S and 1R,3S), occur in fruit juices, juices and fruit purees for infants, and jams. Concentrations in commercially prepared fruit juices were in the ranges 0.01-1.45, 0.02-9.1, and 0.01-2.48 mu g/g for THCA, 1S,3S-MTCA, and 1R,3S-MTCA, respectively. The content was higher in citrus juices (orange, grapefruit) than in other juices (grape, apple, pineapple, peach, banana, pear, tomato). Commercially prepared infant juices contained 0.14, 0.52, and 0.16 mu g/g on average, for THCA, 1S,3S-MTCA, and 1R,3S-MTCA, respectively. Commercial infant fruit purees averaged 0.04, 0.35, and 0.11 mu g/g for THCA, 1S,3S-MTCA, and 1R,3S-MTCA. Jams and marmalades averaged 0.23, 0.76, and 0.25 mu g/g for THCA, 1S,3S-MTCA, and 1R,3S-MTCA, respectively. The reported endogenous presence of these substances in humans could be influenced by their exogenous ingestion in the diet. This is the first specific report on THCA and MTCA in fruit products.