Changes in pigments, total polyphenol, antioxidant activity and color parameters of red and green edible amaranth leaves under different shade levels

This study was conducted to determine the betacyanin, chlorophyll, total polyphenol, antioxidant activity and leaf color parameters of three edible amaranth (Amaranthus tricolor L. subsp. mangostanus L. Allen) cultivars grown under five different shade levels. Red-fleshed leaf cultivars Rocto Alta and Altopati and a greenfleshed leaf cultivar SAT-072 were grown in the open field (no shading) and four selected shading regimes covered by one layer of white, one layer of black, two layers of black and four layers of black neutral density synthetic shading clothes, respectively. The contents of betacyanin, chlorophyll and total polyphenol and antioxidant activity were measured from leaf extracts. Leaf pigments were evaluated in relation to leaf color parameters: lightness (L*), redness (a*) yellowness (b*), chroma (C*) and hue angle (H(0)). The highest content of betacyanin, chlorophyll and total polyphenol and antioxidant activity were found in red-fleshed leaf cultivars grown in full sunlight (open shade). Comparatively, red-fleshed leaf cultivars contained higher amount of pigments, total polyphenol and antioxidant activity than green-fleshed leaf cultivar when exposed to different levels of shade. Highly and strong positive correlations were observed among betacyanin, chlorophyll, total polyphenol and antioxidant activity in red-fleshed leaf cultivars compared to green-fleshed leaf cultivar under different shading conditions. The leaf color of `Rocto Alta' and 'Altopati' gradually changed from red to green with the increasing levels of shade. The variations of pigments caused the wider range of color parameters on red leaf cultivars than on green leaf cultivar.