The influence of polyphenol oxidase and ascorbate oxidase on radical-scavenging activity and contents of total phenol, chlorogenic acid, and ascorbic acid in vegetables during the cooking process were investigated. In the case of burdock and lettuce, which have a high activity of polyphenol oxidase, the radical-scavenging activity and the content of total phenol and chlorogenic acid decreased drastically within 1 min. In the case of broccoli, however, only a small decrease of radical-scavenging activity was observed, and total phenol and chlorogenic acid decreased almost not at all. The decrease of the activity in broccoli depended on the oxidation of ascorbic acid by ascorbate oxidase. None of these compounds decreased after the enzymes had been inactivated by heating.

Epidemiological studies have suggested a protective effect of lycopene and lycopene-rich tomatoes against various cancers. Here, the inhibition of colon carcinogenesis by lycopene and tomato juice was investigated. Seven-week-old female F344/NSlc rats received an intrarectal dose of 2 mg (experiment I) or 4 mg (experiment II) of N-methylnitrosourea 3 times a week for 3 weeks, and had free access to one of 4 drinking fluids: plain water (control group), 17 ppm lycopene water solution (Ly group), and diluted tomato juice containing 17 ppm (Tj group) or 3.4 ppm (tj group) lycopene, throughout the experiments. The colon cancer incidence at week 35 was significantly lower in the Tj group, but not in the Ly group, than in the control group: 21% and 33% vs. 54%, in experiment I (24 rats in each group). It was significantly lower in the Tj group than in the tj and control groups, 40% vs. 72% and 84%, in experiment II (25 rats in each group). An appreciable amount of lycopene (0.02 µ µ µ µg/g) was detected in the colon mucosa of rats in the Tj group, but not in the tj group. The results suggest that tomato juice rich in lycopene may have a protective effect against colon carcinogenesis.

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We determined the serum uric acid-lowering effects of combined daily supplementation of glycine and tryptophan in patients with mild hyperuricemia using a randomized, double-blind, placebo-controlled, crossover clinical trial design. Japanese healthy adult males and females with mild hyperuricemia (fasting serum uric acid of 6.6–7.9 mg/dL) ingested a powder mixture containing 3.0 g of glycine and 0.2 g of tryptophan or a placebo powder once daily at bedtime for 6 weeks. Combined supplementation with glycine and tryptophan significantly decreased serum uric acid levels (from 7.1 mg/dL to 6.7 mg/dL, p = 0.004) before and after the trial. Serum uric acid concentrations significantly decreased in the subjects supplemented with the amino acid mixture compared with those in placebo-treated subjects (p = 0.028). In addition, the combination treatment with glycine and tryptophan decreased serum triglyceride levels (from 119 mg/dL to 86 mg/dL, p = 0.002). Increased solubility of uric acid caused by urinary pH were likely contributors to the serum uric acid-lowering effects of the amino acid mixture.

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