Isolation and characterization of phenolic compounds from Camellia polyodonta flowers: Nobotanin D attenuates lipid accumulation via PI3K/AKT-mediated regulation

Camellia polyodonta (Oil-tea Camellia) flowers are rich in polyphenols but remain underexploited. Although previous studies indicated their hypolipidemic activity, the active compounds and mechanisms were unclear. Seven phenolic compounds were isolated from the 20% ethanol fraction, among which nobotanin D was first reported from this species. In oleic acid-induced steatotic HepG2 cells, all seven compounds reduced lipid accumulation, with nobotanin D exhibiting the strongest effect. Mechanistically, nobotanin D activated the PI3K/AKT pathway and modulated the expression of FOXO1, SREBP-1c, ApoC-III, and MTP, which was associated with reduced intracellular triglyceride accumulation and altered lipoprotein metabolism. It also attenuated oxidative stress (increased SOD, CAT, GSH; decreased MDA) and suppressed apoptosis (upregulated Bcl-2, downregulated Bax). These findings identify nobotanin D as a novel hypolipidemic agent from C. polyodonta flowers for functional food applications.