Relationship of phenolic composition of selected purple maize (Zea mays L.) genotypes with their anti-inflammatory, anti-adipogenic and anti-diabetic potential

This study aimed to investigate the associations between phenolic composition of selected purple maize genotypes and their anti-inflammatory, anti-adipogenic and anti-diabetic properties in vitro. Anthocyanin-rich water extracts (PMWs) from 20 purple maize genotypes were evaluated in RAW 264.7 macrophages and 3T3-L1 adipocytes under different conditions. Cyanidin-3-O-glucoside (C3G), pelargonidin-3-O-glucoside (Pr3G), peonidin-3-O-glucoside (P3G) and corresponding acylated forms were major anthocyanins in PMW, accompanied by ten tentatively identified non-anthocyanin phenolics. Correlation studies showed that C3G, P3G, and derivatives, but not Pr3G and its acylated form contributed to the biological properties of PMW. Besides anthocyanins, quercetin, luteolin, and rutin were the dominant anti-inflammatory and anti-diabetic components, in terms of down-regulating pro-inflammatory mediator production in inflamed macrophages and adipocytes, modulating diabetes-related key enzymes and improving insulin sensitivity in insulin-resistant adipocytes. Quercetin and phenolic acids, especially vanillic acid and protocatechuic acid, were closely associated with anti-adipogenic properties of PMW via inhibition of the preadipocyte-adipocyte transition.