Identification and in vitro anti-inflammatory activity of different forms of phenolic compounds in Camellia oleifera oil

Camellia oleifera (C. oleifera) oil is known as "oriental olive oil". We previously reported the anti-inflammatory activity of C. oleifera oil was mainly attributed to the phenolic compounds, but the specific compounds remain uncovered. In this study, phenolic compounds in the form of free (11.92 μg GAE/g), esterified (37.57 μg GAE/g), glycosylated (128.71 μg GAE/g), and insoluble (47.53 μg GAE/g) were prepared from C. oleifera oil. Their anti-inflammatory activities were evaluated by lipopolysaccharide induced RAW 264.7 macrophage. Glycosylated fraction showed the highest anti-inflammatory activity as indicated by the low production of nitric oxide (NO), tumor necrosis factor-α (TNF-α), interleukin-1β (IL-1β), and interleukin-6 (IL-6). Subsequently, 13 different glycosylated polyphenols were identified by UPLC-Q-TOF/MS, and the major compounds were purified for anti-inflammatory re-evaluation. Lower anti-inflammatory activities of compound 3 and compound 6 were observed when compared to kaempferol. Overall, these results would promote the utilization of phenolic compounds in C. oleifera oil.