Evaluation of Free Radical Scavenging Activity and Toxic Heavy Metal Contents of Commercially Available Fruits of Tribulus terrestris Linn.

Aims: To evaluate the free radical scavenging activity of organic solvent extracts and the toxic heavy metal contents of commercially available fruits sample of Tribulus terrestris Linn in the UAE.

Methodology: Fruit samples were extracted with hexane, ethyl acetate, ethanol and methanol solvents separately and evaluated their total polyphenol contents as well as free radical scavenging activities using 1,1-diphenyl-2-picrylhydrazyl radical assay method. For heavy metal analysis, samples were prepared by a dry ashing digestion procedure and estimated eight heavy metals: cadmium (Cd), lead (Pb), iron (Fe), arsenic (As), aluminum (Al), zinc (Zn), nickel (Ni) and copper (Cu) using Atomic Absorption Spectrometry. Method validation was performed by evaluating metal recovery studies.

Results: The free radical scavenging activities of extracts were compared with known antioxidant L-Ascorbic acid (AA) and the results were decreased in the order of: AA > methanol > ethanol >> ethyl acetate >> hexane extracts. The methanol extract was the most active free radical scavengers due to their higher polyphenols content; ethyl acetate and hexane extracts were not active. The fruits of T. terrestris exhibited a positive response for all tested heavy metals and the concentrations were recorded in 1 g sample as: 37.35±1.29 mg Al, 3.92±0.95 mg As, 0.161±0.037 mg Cd, 2.49±0.34 mg Cu, 87.93±7.87 mg Fe, 1.81±0.61 mg Pb, 0.87±0.13 mg Ni and 8.93±1.59 mg Zn. The estimated heavy metal levels were below the recommended permissible limit set by WHO except As and Fe.

Conclusion: Long time consuming of T. terrestris fruits might implicates an oxidative damages to cells as of their heavy metals contents and in contrary free radical scavenging activity and polyphenolic contents of extracts might give protection against this damages.