In Vitro Studies on The Antioxidant potential of Cyperus rotundus linn. 1. Introduction Antioxidants are compounds that inhibit or delay the oxidation of other molecules by inhibiting the initiation or propagation of oxidizing chain reactions. There are two basic categories of antioxidants, namely, synthetic and natural. In general, synthetic antioxidants are compounds with phenolic structures of various degrees of alkyl substitution, whereas natural antioxidants can be phenolic compounds (tocopherols, flavonoids, and phenolic acids), nitrogen compounds (alkaloids, chlorophyll derivatives, amino acids, and amines), or carotenoids as well as ascorbic acid (Larson, 1988; Hudson, 1990; Hall and Cuppett, 1997). Synthetic antioxidants such as butylated hydroxyanisole (BHA) and butylated hydroxytoluene (BHT) have been used as antioxidants since the beginning of this century. Restrictions on the use of these compounds, however, are being imposed because of their carcinogenicity (Branen, 1975; Ito et al., 1983). Thus, the interest in natural antioxidants has increased considerably (Lo¨liger, 1991). The ability of some phenolic compounds to act as antioxidants has been demonstrated in the literature. Several researchers have investigated the ant oxidative activity of flavonoid compounds and have attempted to define the structural characteristics of flavonoids that contribute to their activity (Nieto et al., 1993; Das and Pereira, 1990; Foti et al., 1996). O-Dihydroxy groups in the B ring, the presence of a C2-3 double bond in conjunction with 4-oxo in the C ring, and 3- and 5-hydroxy groups and the 4-oxo function in the A and C rings are associated with antioxidant activity. Phenolic acids, such as caffeic, chlorogenic, ferulic, sinapic, and pcoumaric acids, appear to be more active antioxidants than the hydroxy derivatives of benzoic acid such as p-hydroxybenzoic, vanillic, and syringic acids (Dziedzic and Hudson, 1983; Larson, 1988). Burton and Ingold (1981) have shown that R-tocopherol is one of the most active in vitro chain-breaking antioxidants. Carotenoids also have a protective function against oxidative damage, and singlet oxygen is very powerfully quenched by â-carotene (Foote et al., 1971). Many of the natural antioxidants, especially flavonoids, exhibit a wide range of
Issuu converts static files into: digital portfolios, online yearbooks, online catalogs, digital photo albums and more. Sign up and create your flipbook.