Natural Antioxidants from Plant Material

Abstract

Natural antioxidants in foods may be from (a) endogenous compounds in one or more components of the food; (b) substances formed from reactions during processing; and (c) food additives isolated from natural sources. Most natural antioxidants are from plants. Most plants contain compounds that possess antioxidant activity. They are polyphenolics that occur in all parts of the plant - wood, bark, stems, leaves, fruit, roots, flowers, pollen and seeds. The antioxidant activities in these plants range from extremely slight to very great. Natural antioxidants may function (a) as reducing agents, (b) as free radical scavengers, (c) as complexers of pro-oxidant metals, and (d) as quenchers of the formation of singlet oxygen. The most common natural antioxidants are flavonoids (flavanols, isoflavones, flavones, catchins, flavanones), cinnamic acid derivatives, coumarins, tocopherols, and polyfunctional organic acids. The antioxidants of plants are phenolics. Some form complexes with metals. However, the major value is in their primary antioxidant activity (i.e., as free radical acceptors and as chain breakers.)