FIG. 1.

Classification of plant phenols. Here, phenols of plant origin are broadly divided into three major groups such as (i) phenolic acids, (ii) flavonoids, and (iii) nonflavonoid polyphenols. Flavonoids are further divided into several classes. Flavonoids such as kaempferol, quercetin, and myricetin fall under the class of flavonols. Genistein and daidzein are classified under the class of isoflavones and thereby are called the soy isoflavones. (-)-epigallocatechin-3-gallate (EGCG) falls under the class of flavanols. These phytochemical phenols as secondary metabolites in plants have definitive roles in plants as the ultraviolet (UV) protectants, wound-healing action, and disease and pest resistance. Primarily, these compounds have established protective actions against oxidative stress as potent, naturally occurring antioxidants.