ANTIOXIDANT POTENCY, pH AND HEAT STABILITY OF SELECTED PLANT EXTRACTS

The potential of methanolic extracts of six green leafy vegetables, viz. Punica granatum, Ipomoea batatas L., Beta vulgaris, Daucus carota, Amaranthus paniculatus and Peucedanum graveolens, as a natural antioxidant was assessed. Two experimental models, namely 1,1-diphenyl-2-picrylhydrazyl radical-scavenging activity and iron (III) reducing capacity, were used to evaluate the antioxidant activity (AOA) of green leafy vegetables. The stability of extracts to pH (4, 7 and 9) and temperature (100C) was investigated. All the extracts showed varying degrees of antioxidant efficacy in a dose-dependent manner. P.granatum had high glutathione and polyphenols, and D.carota had higher ascorbic acid and -carotene. The AOA of D.carota leaves, A.paniculatus and P.graveolens almost remained the same at pH7 and 9. The extracts of D.carota leaves, A.paniculatus and P.graveolens showed increasing AOA after heat treatment. P.granatum was more heat stable than other extracts. PRACTICAL APPLICATIONS Recently, natural plants have received more attention as sources of biologically active substances, including antioxidants, antimutagens and anticarcinogens. Scientific information on the antioxidant properties of various plants that are less widely used in culinary and medicine is scarce. Therefore, six green leafy vegetables (Punica granatum, Ipomoea batatas L., Beta vulgaris, Daucus carota, Amaranthus paniculatus and Peucedanum graveolens) were selected for their antioxidant properties, antioxidant compounds and stability to pH and temperature. P.granatum L. (polyphenol-rich) can be used in food industries, especially in food systems with varied pH. The extracts proved to be better radical scavengers rather than electron donors (reducing power), which depicts the mechanism through which they act as antioxidants. P.graveolens, A.paniculatus, D.carota and P.granatum, due to their heat stability, can be considered as antioxidants in formulations requiring heat treatment.