Anti-inflammatory Properties of Cowpea Phenotypes with different Phenolic Profiles

Abstract

Cowpea (Vigna unguiculata) is a highly nutritious, drought tolerant crop with several agronomic advantages over other legumes. This study demonstrated the association of different cowpea phenotypes with specific phenolic profiles, antioxidants activity, anti-inflammatory properties on non-malignant colonic (CCD18co) cells challenged with a lipopolysaccharide (LPS), and the effect of boiling on their individual and total flavonoid content.

Only the black and green phenotypes had detectable anthocyanins; and their levels were highest in the black IT95K-1105-5 variety. The red cowpea phenotypes had the highest level of flavonols (858 - 941 micrograms/g cowpea flour) and white Early Acre variety had the least. Quercetin derivatives were the major flavonols detected, followed by myricetin derivatives. Monomeric, dimeric and polymeric procyanidins also made up a large proportion of cowpea phenolics. The light brown 09FCV-CC27M cowpea variety had the highest average flavan-3-ol content (13,464 micrograms/g cowpea flour); whereas white and green varieties did not contain detectable levels of flavan-3-ols. Thus, seed-coat color was a good indicator of the accumulation of specific flavonoids in cowpeas.

The black, red and light-brown cowpeas had the highest antioxidant activity measured by ORAC and ABTS methods, correlating with their higher total phenol content (TPC) and condensed tannin content (CTC); whereas the white and green varieties had the least. Boiling significantly affected the phenolic profiles, TPC and CTC of all cowpea varieties studied, as well as the antioxidant activity associated with these compounds. The net reduction in antioxidant activity after boiling was less than the net TPC reduction, indicating that the heat-induced phenolic products may still have radical scavenging capacity.

Overall, proinflammatory genes regulation, intracellular ROS inhibition, and modulation of miR-126 and its target gene VCAM-1 by cowpea were found to be dependent on cowpea variety, phenolic composition and concentrations. The underlying mechanism by which cowpea induced miR-126 may be associated with inhibition of ROS and down-regulation of transcription factor NF-These results emphasize the importance of the cancer inhibitory potential of phenolic compounds from cowpea and their possible role in preventing anti-inflammatory disorders. Further in vivo studies with cowpea diets are required to validate their clinical relevance to human health.