Estimation of antioxidant and hypolipidemic activities of extracts of Citrus x aurantium leaves in vitro

• The first study on hypolipidemic role of Citrus x aurantium var. amara L. leaves. • The decoction extract has the highest phenolic and flavonoids contents. • The antioxidant capacity of decoction extract is stronger than other extracts. • All extracts show bile acid binding activity with concentrations of ≤ 0.5 mg/mL. This study was done to estimate the antioxidant and hypolipidemic activities of three extracts of Citrus x aurantium var. amara L. leaves, and to determine the total phenolic and flavonoids contents, as well as to find the relationship between leaves’ chemical (phenolic and flavonoids) content and their biological activities. Three different extracts were prepared using distilled water, ethanol 70 %, and n-hexane. The Folin-Ciocalteu assay was used to determine the total phenolic content of extracts. The aluminum chloride assay was used to determine the total flavonoids content of extracts. The antioxidant activity of various concentrations of extracts was estimated by measurement of the ability of each extract to scavenge 1,1-diphenyl-2-picrylhydrazyl (DPPH) free radical. Hypolipidemic activity of various concentrations of extracts was estimated by measurement of the bile acid binding capacity. The water extract, which was obtained by decoction, showed the highest phenolic and flavonoids contents (268.948 ± 1.131 mg GAE/g DW and 50.676 ± 0.659 mg QE/g DW, respectively) followed by hydroalcoholic and hexanic extracts (243.732 ± 3.726, 215.870 ± 4.763 mg GAE/g DW, and 43.312 ± 1.506, 41.226 ± 0.967 mg QE/g DW, respectively; p < 0.05). IC 50 values of DPPH scavenging activity were lower in water extract than hydroalcoholic and hexanic extracts (0.324 ± 0.025, 0.403 ± 0.009, and 0.414 ± 0.024 mg/mL, respectively; p < 0.05). All extracts showed bile acid binding activity with IC 50 values of 0.347 ± 0.011, 0.388 ± 0.004, and 0.400 ± 0.011 mg/mL for water, hydroalcoholic, and hexanic extracts, respectively. There were high correlations between each of phenolic and flavonoid content and the biological activities of leaves’ extracts ( p < 0.05). The water extract has the highest phenolic and flavonoids contents. Citrus x aurantium leaves’ extracts possess antioxidant and hypolipidemic activities in vitro . Properties observed indicate the usefulness of Citrus x aurantium leaves in managing hyperlipidemia and obesity worldwide.