Identification and evaluation of antioxidants defatted Camellia oleifera seeds by isopropanol salting-out pretreatment

Seven flavonoid glycosides (1–7) and one theasaponin (8) were isolated from the defatted Camellia oleifera seeds using the isopropanol salting-out pretreatment (ISP) technique, followed by column chromatography. Among them, compounds 5, 7, and 8 are new compounds. The comparison of oxygen radical absorbance capacity (ORAC) of crude extracts extracted by the n-butanol partition (BP) with those extracted by the ISP showed that the latter method yields eight times greater scavenging capacities than that of the former approach. Besides, ISP exhibited almost twice the extraction efficiency than that of BP. ORAC and Trolox equivalent antioxidant capacity (TEAC) analysis revealed that the most potent antioxidants are compounds 1 and 2, which exhibited 1.78 and 1.41 times higher antioxidant activity than that of Trolox, respectively. These results indicated that the ISP approach improves the extraction efficiency in the isolation of potent antioxidants, making the defatted C. oleifera seeds valuable in the food additive industry.