Cyril Auger

The absorption, metabolism and excretion of flavan-3-ols and procyanidins following the ingestion of a grape seed extract by rats

Rats were fed a grape seed extract (GSE) containing (+)-catechin, (-)-epicatechin and dimers, trimers, tetramers and polymeric procyanidins. Liver, kidney, brain and gastrointestinal (GI) tract together with plasma, urine and faeces were collected over a 24 h period and their flavan-3-ol content was analysed by HPLC with tandem mass spectrometry and diode array detection. Small amounts of the GSE flavan-3-ols moved out of the stomach and into the duodenum/jejunum, and to a greater extent the ileum 1 h after ingestion, and into the caecum after 2 h with relatively small amounts being detected in the colon after 3 h. The GI tract contained the parent GSE flavan-3-ols and procyanidins with only trace amounts of metabolites and there were no indications that proanthocyanidins were depolymerised in the GI tract releasing monomeric flavan-3-ols. Plasma contained exclusively catechin glucuronides and methylated glucuronide metabolites which were also detected in the liver and kidneys. These metabolites were also present in urine together with sulphated metabolites and low amounts of the procyanidin dimers B1, B2, B3 and B4 as well as the trimer C2 and an unknown GSE trimer. The amounts of (+)-catechin and (-)-epicatechin metabolites excreted in urine relative to the quantity of the monomers ingested were 27 and 36 %, respectively, after 24 h. This is similar to the levels of urinary excretion reported to occur by other investigators after feeding (-)-epicatechin to rats and provides further, albeit indirect, evidence that the procyanidin oligomers in the GSE were not depolymerised to monomers to any extent after ingestion. No convincing analytical data were obtained for the presence of flavan-3-ol metabolites in the brain.

Phenolics from purple grape, apple, purple grape juice and apple juice prevent early atherosclerosis induced by an atherogenic diet in hamsters.

Knowledge of the effects of processing on the antioxidant properties of fruits is limited. We investigated the processing of apple (A) and purple grape (PG) and their juices (AJ and PGJ) in hypercholesterolemic hamsters. Five groups of eight hamsters each were fed an atherogenic diet for 12 wk. They received daily by gavage either 7.14 mL/(kg x day) of mashed A or PG, or the same volume of AJ or PGJ, or water as control. Plasma cholesterol, non-HDL cholesterol, liver superoxide dismutase and glutathione peroxidase activities, and thiobarbituric acid reactive substances were efficiently reduced by the fruits and their juices compared with controls, whereas plasma antioxidant capacity was increased and aortic fatty streak area was decreased from 48 to 93%. For each of these parameters, the efficacy was PGJ > PG > AJ > A. The results show for the first time that long-term consumption of antioxidants supplied by apple and purple grape, especially phenolic compounds, prevents the development of atherosclerosis in hamsters, and that processing can have a major impact on the potential health benefits of a product. The underlying mechanism is related mainly to increased antioxidant status and improved serum lipid profile.

The effect of black tea on risk factors of cardiovascular disease in a normal population

OBJECTIVES A prospective randomized controlled clinical trial determined the effect of Mauritian black tea consumption on fasting blood plasma levels of glucose, lipid profiles and antioxidant status in a normal population. METHODS The study group (71%) consumed 3 x 200 ml of black tea infusate/day for 12 weeks without additives followed by a 3 week wash-out. The control group (29%) consumed equivalent volume of hot water for same intervention period. RESULTS The tea used had high levels of gallic acid derivatives (50 ± 0.4 mg/L), flavan-3-ols (42 ± 2 mg/L), flavonols (32 ± 1 mg/L) and theaflavins (90 ± 1 mg/L). Daily 9 g supplementation of black tea infusate induced, in a normal population, a highly significant decrease of fasting serum glucose (18.4%; p<0.001) and triglyceride levels (35.8%; p<0.01), a significant decrease in LDL/HDL plasma cholesterol ratio (16.6%; p<0.05) and a non significant increase in HDL plasma cholesterol levels (20.3%), while a highly significant rise in plasma antioxidant propensity (FRAP: 418%; p<0.001) was noted . CONCLUSION Black tea consumed within a normal diet contributes to a decrease of independent cardiovascular risk factors and improves the overall antioxidant status in humans.