Phenolic composition and mammary cancer cell inhibition of extracts of whole cowpeas ( Vigna unguiculata) and its anatomical parts

Abstract

The phenolic profile and anticancer properties of extracts from whole cowpeas, seed coats and cotyledons were determined. Seed coats contained at least 5 and 10 times more free and bound phenolics compared to whole seeds (75.6 and 31.7 mg/100 g of free and bound phenolics, respectively). Seed coats and cotyledons contained about 50% and 95% of free phenolics, respectively. The major phenolics associated to seed coats were gallic and protocatechuic acid, whereas in cotyledons p-hydroxybenzoic acid was prevalent. Seed coats contained approximately 10 times more flavonoids compared to whole seeds and cotyledons were practically free of flavonoids. After acid hydrolysis, myricetin, quercetin and kaempferol were identified in seed coats. Most of the antioxidant activity determined with the 2,2′-azino-bis(3-ethylbenzothiazoline-6-sulfonic acid) (ABTS) and oxygen radical absorbance capacity (ORAC) assays was exerted by free phenolics. The free phenolic extract of whole seeds at a concentration of approximately 100 mg gallic acid equiv. (GAE)/l inhibited 65% the proliferation of hormone-dependent mammary (MCF-7) cancer cells. Extracts of seed coats or cotyledons also inhibited cell proliferation but to a significantly lesser extent, thus indicating synergistic effects between phenolics and other phytochemicals associated to these anatomical parts.