Background – Diet based strategies to promote cardiovascular health are becoming increasingly popular, and recent studies have identified potential therapeutic roles in human health for specific dietary components (bioactives). At present, the main heart health ingredients are those with strong scientific evidence for their efficacy (eg n-3 PUFAs; plant sterols). The market for foods to promote heart health is expected to grow 60% in the next 5 years, and therefore high demand exists for novel bioactives so long as they are backed by good scientific evidence.
Objective – 1) To develop a robust bioactive discovery process spanning from identification of target mechanisms, in vitro screening assays to pre-clinical substantiation in animal models prior to validation in humans; 2) To assess vascular relaxation actions of different plant and grape seed extract (GSE) and fractions on different blood vessel preparations representing conductance and resistance vessels of the normotensive WKY (Wistar-Kyoto) rat.
Design – Thoracic aorta, intact mesenteric vascular bed and the third arcade of mesenteric arteries (250-350 micron diameter) were isolated from 20 week old rats. Aortic rings (3 mm) were mounted under 4 g resting tension while the mesenteric bed was perfused continuously with oxygenated Krebs-Henseleit buffer. The micro-vessels were studied using a myograph. Test extracts were added cumulatively to vascular preparations pre-contracted with noradrenaline and the extent of relaxation recorded. GSE extracts were provided by Tarac Technologies (SA).
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Outcomes – In the aortic ring preparation, different GSE extracts - polymeric fraction and Vinlife – caused the
greatest relaxation (80-90%) followed by the oligomeric fraction while the monomeric fraction was least effective as evident by a rightward shift in the dose-response curve. Similar profile was apparent for the perfused mesentery.
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Only the Vinlife preparation resulted in a dose-dependant relaxation of the micro-vessels. Several other plant
extracts caused relaxations in aortic rings ranging from 30-97% that were endothelium dependant. Lemongrass extract showed preferential relaxation in the mesenteric bed that may be mediated via cannabinoid (CB1) receptors. Conclusions – The observed differences in vascular relaxation among different GSE preparations may be due to compositional differences in the polyphenols.