Sensory Characteristics and Impact of Flavanol-Rich Grape and Blueberry Extract on Blood Flow Velocity and Oxidative Stress.

Background: Several epidemiological studies and intervention trials have demonstrated that grapes and blueberries, which are rich in flavanols, can lower the risk of cardiovascular disease. However, the mechanisms of action of these compounds remain unclear due to their low bioavailability.

Objective: This study aimed to characterize the sensory properties, blood flow velocity, and oxidative stress of a polyphenol rich grape and blueberry extract (PEGB) containing approximately 16% flavanols (11% monomers and 4% dimers).

Method: A sensory property of PEGB was compared with quercetin at uniform concentration using healthy young subjects. In addition, the reactivity of PEGB with O₂^•- was also compared with quercetin utilizing a luminescence method. Furthermore, the effect of a single administration of PEGB on the blood flow velocity of skeletal muscle arterioles was investigated using a laser Doppler method in rats.

Results: At a concentration where quercetin was barely tasteful, flavanol in PEGB exhibited a robust astringent taste. Furthermore, under pH conditions mimicking the oral cavity and intestinal tract, PEGB promoted O₂^•- production at low concentrations and scavenging O₂^•- at high concentrations. In contrast, quercetin demonstrated antioxidant activity. A single oral administration of PEGB significantly increased the blood flow velocity of skeletal muscle arterioles.

Conclusion: The results demonstrate that PEGB exhibited a pronounced astringent taste, O₂^•- production at low concentrations in neutral pH environments, and significantly enhanced blood flow to skeletal muscle following a single administration to rats. These findings highlight the necessity for further investigation into the causal relationships between oral perception, redox properties, and bioactivity of polyphenols.