Effects of extraction solvents on the antioxidant and phytochemical activities of manihot esculenta leaves

Abstract

Background: Plants contain diverse phytochemicals with different solubility levels, depending on their molecular charges and polarity. This study was conducted to examine the effects of three extraction solvents in their pure and aqueous forms: absolute petroleum ether, acetone and ethanol on the phytochemical profile and antioxidant activities of Manihot esculenta leaves extracts. Methods: The preliminary phytochemical investigations were performed, using standard procedures. The in vitro antioxidant properties were estimated by: 1,1-Diphenyl-2-Picryl-Hydrazyl (DPPH), Hydrogen peroxide (H2O2) scavenging activity, Ferric Reducing Antioxidant Power (FRAP) and Ferric Thiocyanate (FTC). Results: The phytochemical analyses revealed the occurrence of an array of compounds: alkaloids, flavonoids, cardiac glycosides, tannin phenols, saponins and anthraquinones, the concentration of which varied with the solvent type. A considerable presence of all phytochemicals was found in the aqueous ethanol. The extracts from pure solvents were much less effective against DPPH synthetic radical than those 50% diluted. The petroleum ether extract provided the least antiradical activity, while the aqueous ethanol was the richest. The scavenging effect of the extracts on H2O2 varied in this order: 50% ethanol > absolute ethanol > ascorbic acid > 50% acetone > absolute acetone > 50% petroleum ether > absolute petroleum ether. Similarly, the results of the FRAP and FTC methods agreed largely with those of the DPPH and H2O2. Thus, the results of antioxidant activity positively correlated with the phytochemical results, with the aqueous ethanol showing the maximum activity overall. Conclusion: The results indicated that the extraction solvents considerably affected the phytochemical contents and the antioxidant activities of the tested extracts. These extracts can potentially serve as the alternative sources of natural antioxidant preparations.