Major chemical constituents and antioxidant activities of different extracts from the peduncles of Hovenia acerba Lindl

Hovenia acerba Lindl. is a perennial tree of Rhamnaceae family. In the present study, four solvents (80% methanol, ethyl acetate, n-hexane, and water) were used to extract the compounds of Hovenia acerba Lindl. peduncles (HAP). The total contents of phenolics and tannins (TPC and TTC), as well as their antioxidant activities (DPPH, ABTS, and FRAP) of these four different extracts including 80% methanol extract (ME), ethyl acetate extract (EE), n-hexane extract (HE) and water extract (WE) were compared. The antioxidant activities of HAP showed positive correlations with TPC and TTC, indicating that phenolics maybe a major contributor to the antioxidant activities of HAP. The significant difference between antioxidant activities and TPC/TTC implied the respective contribution extent of phenolics for the antioxidant activities of four solvent extracts. Besides, a total of 117 compounds, including 7 oligosaccharides, 11 organic acids, 41 phenolics, 1 steroids, 25 terpenes, 11 fatty acids, 9 amino acids, and 12 other compounds were identified or tentatively characterized in HAP for the first time. Among them, 23 bioactive constituents, including 4 organic acids, 5 phenolic acids, and 14 flavonoids, were quantified. The comparison of characterization and quantitation of 4 extracts demonstrated that 80% methanol showed the widest range of selectivity for both HAP flavonoid aglycones and glycosides, while ethyl acetate preferred to extract the flavonoids aglycone from HAP. Secondly, water and 80% methanol were excellent solvents for the extraction of phenolic acids. And both ethyl acetate and 80% methanol perform well at the extraction of terpenes and steroids.