Assessment of antioxidant potentials of free and bound phenolics of Hemidesmus indicus (L) R.Br against oxidative damage

Background: Hemidesmus indicus R.Br. is a twining shrub commonly found in India, which was known to have wide pharmacological actions. 2-hydroxy-4-methoxy-benzoic acid (HMBA) and a number of pregnane glycosides were believed to be responsible for its various bioactivities. Until now, there are no reports regarding the antioxidant properties of phenolics from H. indicus. Objective: To establish the role of phenolics in the properties of H.indicus. Materials and Methods: Hemidesmus free phenolic fraction (HDFP) and Hemidesmus bound phenolic fraction (HDBP) have been isolated from H. indicus, and the antioxidant activity was evaluated for inhibition of lipid peroxidation, DNA protection, free radical scavenging (FRS), reducing power and cytoprotective activities. Results: HDFP and HDBP exhibited potent inhibition of lipid peroxidation (IC50 - 19.5 +/- 0.5 and 21.7 +/- 0.5 mg gallic acid equivalent - GAE/mL), FRS (IC50 - 7 0.2 and 8.6 0.2 mgGAE/mL), reducing power (110.3 +/- 2 and 33.5 +/- 1 U/g) and red blood cell protection (14.8 +/- 0.4 and 14.5 +/- 0.5 mg GAE/mL). HDFP is constituted by gallic (18%), caffeic (17%), ferulic acids (16%) and HDBP by syringic acid (35%) as major phenolic acids. Besides, both HDFP and HDBP contained significant levels of HMBA; in HDFP (10%) and HDBP (57%), respectively. Results indicated a 34-and 27-folds better contribution to the antioxidant activity by HDFP and HDBP, respectively, than that of HMBA. Conclusion: Potent antioxidant activities of phenolics may be one of the mechanisms by which H.indicus is effective against several health disorders as encountered in traditional medicines.