Abstract: The contents and major compositions of free phenolics (FP), esterified phenolics (EP) and insoluble-bound phenolics (ISP) from camellia seed oil were analyzed. The ferric ion reducing antioxidant power, 2,2’-azino-bis(3-ethylbenzothiazoline-6-sulfonate) (ABTS) cation radical scavenging capacity, 2,2-diphenyl-1-picrylhydrazyl (DPPH) radical scavenging capacity and β-carotene bleaching capacity were used to study the antioxidant activity of the three phenolic compounds and their interactions. The results showed that the content of total phenols in camellia seed oil was (137.97 ± 5.14) mg/kg. ISP was significantly more abundant than FP and EP (P < 0.05), which accounted for 47.74% of the total phenols in the oil. In addition, benzoic acid derivatives (mostly isovanillin and methyl vanillin) were the dominant component in FP, salicylic acid was the dominant component in EP, and 3,4-dihydroxymandelic acid was the dominant component in ISP. The three forms of phenolic compounds showed different antioxidant capacities with different mechanisms in a concentration-dependent manner. FP + ISP and EP + ISP showed a synergistic and additive interaction in the antioxidant tests, the antioxidant activity of the latter combination being stronger than that of the former. However, FP + EP and FP + EP + ISP showed an antagonistic or additive effect.

Key words: camellia seed oil; free phenolics; esterified phenolics; insoluble-bound phenolics; antioxidant; interaction