Effect of solvent on the Extraction of Constituents from the leaves of Olea Europaea and their 2,2-diphenyl-1-Picrylhydrazyl radical scavenging assay

Abstract

Olive leaf extracts were prepared using the maceration method with a series of solvents of varying polarities, including n-hexane, dichloromethane, ethyl acetate, nitrobenzene, methyl ethyl ketone, acetone, methanol, and acetonitrile. Among the solvents, methanol yielded the highest extract content (26.8%), followed by nitrobenzene (18.4%), acetone (11.2%), ethyl acetate (10.4%), dichloromethane (9.2%), methyl ethyl ketone (6.8%), acetonitrile (3.6%), and n-hexane (0.96 %). The antioxidant activity of these extracts was assessed using the DPPH (2,2-diphenyl-1-picrylhydrazyl) radical scavenging assay. At a concentration of 120 ppm, the percentage inhibition of DPPH radicals was highest for ascorbic acid (96.49%), followed by methanol (90.45%), ethyl acetate (85.58%), acetone (78.75%), and methyl ethyl ketone (66.28%). Lower inhibition was observed for acetonitrile (55.36%), nitrobenzene (39.77%), dichloromethane (38.01%) and n-hexane (28.07%). The antioxidant activity, evaluated using IC₅₀ values (where lower values indicate higher antioxidant potential), identified ascorbic acid as the most potent standard (IC₅₀ = 7.03 µg/mL). Among the samples, the n-hexane extract demonstrated the weakest antioxidant activity (IC₅₀ 206.09 µg/mL), while the methanol extract exhibited the strongest (IC₅₀ = 35.88 µg/mL). Other extracts showed IC₅₀ values of 157.77 µg/mL for dichloromethane, 155.10 µg/mL for nitrobenzene, 113.18 µg/mL for acetonitrile, 80.98 µg/mL for methyl ethyl ketone, 54.18 µg/mL for acetone, and 40.29 µg/mL for ethyl acetate. These results underscore the influence of solvent polarity on both extraction efficiency and antioxidant activity, with polar solvents generally yielding higher antioxidant potential.