The effect of different drying methods on chemical composition and antioxidant properties of methanolic extract of olive leaf

Olive leaf consumption due to its antioxidant properties and several applications in medicine and pharmaceutical sciences is considered from ancient time. In this research effect of different drying methods including oven drying at 60 °C and 105 °C, microwave drying at 400 W and 700 W and shadow on methanolic extraction of olive leaf were evaluated. Antioxidant properties were assayed using 2,2-diphenyl-1-picrylhydrazyl (DPPH), ABTS, and ferric reducing ability of plasma (FRAP) and also total phenolic and flavonoid content were measured using Folin-Ciocalteu and aluminum chloride respectively. Olive leaf contains 55.17% moisture, 6.12% ash, 3.18% fat, 8.21% protein, 8.58% polysaccharide, 18.48% insoluble carbohydrate, and 27.32% total carbohydrate. Results showed that drying method affect antioxidant properties and phenolic and flavonoid extraction significantly. By increasing the concentrations of extracts, their anti-radical activity increased and the radical scavenging ability of extracts depended on their concentration. Highest antioxidant property were seen in 400 W microwave and the lowest results were in oven drying at 60 °C.