Comparative profiling of polyphenols and antioxidants and analysis of antiglycation activities in rapeseed (Brassica napus L.) under different moisture regimes.

Genotype, growth stages, and moisture regimes affect polyphenols as beneficial compounds in rapeseed with edible and medicinal properties. The aims of this study were to assess the effects of tissue, genotype background and moisture on growth, pigment composition, phenolic acids, flavonoids, antioxidant, and antiglycation activities in rapeseed. Treatments included two moisture regimes (10% field capacity as drought-treated and 30% field capacity as control), tissue (leaf, flower and seed), and 12 rapeseed genotypes. The range of loss in growth traits under drought compared with control was between 23% and 47%. Drought reduced number of leaves, leaf area, fresh and dry weights by 23%, 31%, 37%, and 36%, respectively whilst increased chlorophylls, carotenoids, total pigment, phenolic compounds, flavonoids, and antioxidant activities. Analysis for antiglycation properties in two genotypes (G01 and G08) which accumulated higher phenolic compounds showed that higher antiglycation property was associated with higher epicatechin, and caffeic, and syringic acids. Flower extracts showed higher phenolics than leaf and seed suggesting flowering stage is a preferred timing to harvest a higher polyphenols from rapeseed. Overall, our results demonstrated role of specific polyphenols in antiglycation activities and the importance of growth stage and genotype in attaining higher polyphenols and antioxidants that affect edible and medicinal values of rapeseed under water limited conditions.