Free and bound phenolic antioxidants in amla (Emblica officinalis) and turmeric (Curcuma longa)

The antioxidant activity of free and bound phenolics of amla (Emblica officinalis) and turmeric (Curcuma longa) was investigated. The Emblica officinalis free (EOFP) and bound phenolics (EOBP) showed between four- to 10-fold higher levels of antioxidant activity as evaluated by both free radical scavenging and reducing power assays compared to that of Curcuma longa free (CLFP) and bound phenolics (CLBP). Higher level of antioxidant activity in E. officinalis has been attributed to the phenolic content (12.9%, w/w, correlation coefficient R = 0.74 ) in them. The free and bound phenolics of E. officinalis showed high content of phenolic compounds (126 and 3.0 mg/g) compared to that of C. longa (29.7 and 1.6 mg/g). Gallic acid and tannic acid were identified as the major antioxidant components in phenolic fractions of E. officinalis. The antioxidant activity of CLFP could be attributed to curcumin and that of CLBP to ferulic acid and p-coumaric acid. Further, the extracts of both E. officinalis and C. longa also exhibited significant protection to DNA against oxidative damage as evidenced by migration of DNA on the agarose gel. Our results clearly suggest the presence of potent antioxidants such as gallic acid in E. officinalis and protocatechuic acid and ferulic acid in C. longa, in addition to the known ascorbic acid and curcumin in E. officinalis and C. longa, respectively.