Multi-omics analysis reveals flavor biosynthesis in Camellia seed oil: phenylpropanoid pathway activation and antioxidant modulation of lipoxygenase (LOX)

Camellia is a widely cultivated woody oil plant in southern China that produces high-quality edible oil rich in unsaturated fatty acids and bioactive compounds. This study conducted a comprehensive multi-omics comparative analysis of oil quality (fatty acid composition, bioactive compounds, antioxidant activity, volatile flavor compounds, and metabolomic profiles) of camellia seed oils from Hainan, Jiangxi, and Guangxi. Results showed that Camellia hainanica (Hainan variety) had lower seed oil content (39.19%–46.24%) compared to Jiangxi (48.45%–52.99%) and Guangxi (47.16%–59.46%) varieties but significantly higher levels of polyphenols, flavonoids, squalene, carotenoids, and amino acids, resulting in a stronger antioxidant capacity. Fatty acid analysis revealed higher saturated fatty acid (SFA) levels in C. hainanica , while C. oleifera varieties from Jiangxi and Guangxi production areas were richer in monounsaturated fatty acids (MUFAs). Volatile profiling identified 45 metabolites, with C. hainanica distinguished by unique terpenoids and a more complex aroma. Non-targeted metabolomics revealed two main mechanisms behind flavor differences: (1) tropical stress can cause overactivation of the phenylpropanoid pathway in Hainan oil-tea camellia, leading to the production of strong antioxidant phenolic compounds and phenylpropanoid matrices; (2) the LOX pathway facilitates the breakdown of polyunsaturated fatty acids and results in the accumulation of nonanal, which is the key process behind the characteristic “grass-like aroma” of Jiangxi tea seed oil. Additionally, the metabolism of this pathway may be heavily influenced by high antioxidant substrates produced endogenously.