Assessments of extraction methods onto the phenolic profiles and antioxidant properties in Camellia oleifera Abel oils

Camellia oleifera Abel is a traditional and high-quality oil source in China, characterized as polyphenols. This study evaluated how extraction methods impacted the phenolic profiles and antioxidant activities of Camellia oils. The contribution rates of phenolic profiles to antioxidant activities were investigated. HPLC and UPLC-Triple-TOF/MS demonstrated that phenolic content significantly varied with extraction methods while phenolic profiles were not. Herein, 15, 15, 17, 14, and 14 compounds were identified in mechanical pressing (MP), solvent extraction-hexane (SE-H), solvent extraction-ethanol (SE-E), aqueous enzymatic extraction (AEE), aqueous extraction (AE) oils, respectively. Results presented that SE-E oils were rich in phenolic acids (caffeic acid and p-hydroxybenzaldehyde), while AE oils were abundant in flavonoids (rutin and quercetin). Besides, the antioxidant activities of AEE and AE oils were significantly higher than other oils, originating from flavonoids (rutin and quercetin) and non-phenolics (rhododendron acid). Furthermore, Camellia oils from five extraction methods were remarkably classified by principal component analysis based on phenolic categories and antioxidant activities. It was assumed that low-polar and high-polar phenolic profiles were simultaneously transferred into SE-E oils, while only low-polar phenolic profiles (mainly flavonoids) were extracted into AE or AEE oils. The antioxidative origin of Camellia oils was ascribed to rutin, quercetin, and rhododendron acid. Our results provided an in-depth understanding of Camellia oils on phenolic profiles and the relationship between extraction methods and antioxidant activities.