Cacao polyphenolic substances. I. Fractionation of the fresh bean

Ingestion of Proanthocyanidins Derived from Cacao Inhibits Diabetes-Induced Cataract Formation in Rats

Proanthocyanidins derived from cacao (CLP) have various antipathophysiological functions. We have tested whether dietary supplementation with CLP prevents cataract formation in rats with diabetes induced by streptozotocin (STZ), using histological, histochemical, and biochemical analyses. Starting at 7 days after the streptozotocin challenge, the animals were fed either a normal diet or a diet containing 0.5% w/w CLP over 10 weeks. There were no significant differences in plasma and urine glucose concentrations, plasma fructose amines, and plasma thiobarbituric reactive substances (TBARS) between the two dietary groups. Antioxidant status as assessed by measuring lipid peroxide production in plasma in response to azocompounds was lower in the STZ-rats fed control diet than in animals fed CLP. Opacity was first detected in the lenses of the control dietary group 5 weeks after STZ injection and cataracts had developed in the majority of these animals by 10 weeks. These changes were rarely seen in the STZ/CLP diet group. Histological examinations of the eyes of the STZ-treated normal diet group revealed focal hyperplasia of the lens epithelium and liquefaction of cortical fibers. There were similar but considerably less severe changes in the animals fed CLP. Hydroxynonenal (HNE), a marker of oxidative stress, was detected immunohistochemically in the lenses of the STZ-treated normal diet group, but not of those receiving CLP. Our findings suggest that CLP inhibits diabetes-induced cataract formation possibly by virtue of its antioxidative activity.

CONVERSION OF LEUCOANTHOCYANINS INTO THE CORRESPONDING ANTHOCYANIDINS

Purified preparations of leucoanthocyanins from several sources were heated in butanol-hydrochloric acid solutions from 50 degrees to 90 degrees C and the rate of production of cyanidin was measured. From the temperature dependence of this rate, the calculated energy of activation was of the order of magnitude of 20,000 calories. The rate-limiting step in this reaction was similar for two preparations tested, and of lower energy for a third, presumably of lower degree of polymerization.