Relationship among colors, pigments, and antioxidant activities of pineapple leaves

Twenty-two pineapple (Ananas comosus) cultivars were used to study the relationships among five color parameters (L^*, a^*, b^*, c^*, and h^* values), five pigment types (chlorophyll, carotenoids, anthocyanins, flavonoids, and total phenols), and three antioxidant activity indices (ABTS, DPPH, and nitrite assay) of leaves. The results indicated that color parameters a^* and h^* were important indicator indices for color, main pigment content, and antioxidant activity of pineapple leaves. The main pigment composition of the pineapple leaves was chlorophyll, flavonoids, and total phenols, with a small amount of anthocyanins and almost no carotenoids. Correlation analysis indicated that antioxidant activity was significantly positively correlated with flavonoid and total phenol content, but chlorophyll content was not significantly correlated with the other indicators. Flavonoids and total phenols were the main active compounds of antioxidant activity in pineapple leaves.