Phenolic Compounds In Plants

1.10. Caffeic acid

Phenolic compounds are secondary plant metabolites and widely distributed in plant kingdom. These compounds are simple phenols because of their structure. Hydroxycinnamic acid is the major subgroups of phenolic compounds (Sroka and Cisowski, 2003).It has been phenylpropanoid metabolites and occur widely in plants (Herrmann, 1989) and plant products (Clifford, 1999). Hydroxycinnamates and their derivates are bioactive plant food ingredients. They exhibit in vitro antioxidant activity, which might have beneficial health impact in vivo (Kroon and Williamson, 1999). Among the polyphenolics, caffeic acid (3,4-dihydroxycinnamic acid) has been found to be a major hydroxycinnamic compounds. It has conjugates as chlorogenic and quinic

Numerous experimental reports postulated that consumption of caffeic acid possess strong antioxidant properties for scavenging free radical activity (). It has been reported that CA inhibited in a dose-dependent manner in human LDL lipoperoxidation induced by cupric ions (). The authors show that CA is able to suppress lipoperoxyl radicals (ROO•) by donating a hydrogen atom to its corresponding hydroperoxide, which inhibits the lipid peroxidation chain reaction ().The antioxidant effect of CA against membrane lipid peroxidation was more pronounced than on the other systems, in which it prevented the peroxidation in lower concentrations. This higher antioxidant activity could be due to the hydrophobicity of CA, which would increase its antioxidant activity in a lipophilic environment. In this system, CA could intercalate between the phospholipids present in biological membranes, acting as a peroxyl radical scavenger. Moreover, CA could chelate iron ions in the membrane microenvironment, preventing both initiation and propagation of lipid

Recent experimental evidence suggests that caffeic acid is a potent antioxidant and might have beneficial health impact in vivo (Jayanthi and subash 2010). Caffeic acid has several biological and pharmacological properties, such as antiviral, antioxidants, anti inflammatory, anticarcinogenic, and immunomodulatory activites. It has been shown that caffeic acid inhibits both lipoxygenase activity and suppresses lipid peroxidation (). Caffeic acid has been completely blocks the generation of reactive oxygen species (ROS) and xanthine/xanthine oxidase system. Previously, we reported that caffeic acid prevents oxidative damage in UVB irradiated human blood lymphocytes (Prasad et al., 2009). Caffeic acid protected human KF1 diploid fibroblast and A431 epidermoid carcinoma cell lines from UVC-induced cytotoxicity [7]. It was shown to inhibit UVB radiation-induced IL-10 expression and the activation of the mitogen-activated protein kinases (MAPKs) in mouse skin (Staniforth et al., 2009). In a recent work, it was shown caffeic acid inhibited the cell proliferation of HepG2 cells in a dose dependent manner. Moreover it has been blocked the MMP-9 expression by inhibiting the NF-κB activity. Further, evidence showed that caffeic acid at a dose of 20 mg/kg retarded the growth of HepG2 tumor xenografts in