Phytochemical investigation of Camellia flava leaves guided by response surface method-optimized extraction: New triterpenoid saponins and flavonoid glycosides.

Camellia flava has recently gained attention for its reported biological activities, but its phytochemical composition remains largely unexplored. In this study, we systematically optimized the extraction of saponin-rich fractions from C. flava leaves using response surface methodology coupled with a Box-Behnken design. The optimal extraction parameters were determined as 50% (v/v) ethanol in water, with a liquid-to-solid ratio of 42.4 mL/g, at 57 °C (extraction temperature), for 4.2 h (extraction time), yielding an extract with a total saponin content of approximately 70 mgRb1E/g. Further, phytochemical investigation of the optimized extract led to the isolation and characterization of four specialized metabolites, including three new glycosides: Camelliaursanoside A, Camelliaoleanoside A (new triterpenoid saponins) and Camelliakaempferoside A (a new acetylated kaempferol glycoside) together with the known flavonoid glycoside: mauritianin. The isolated molecules were characterized using different spectroscopic and spectrometric techniques, including 1D and 2D NMR, HR-ESI-MS, and FT-IR analysis. The sugar residues were further confirmed by acid hydrolysis followed by derivatization and HPLC-DAD, MS/MS analysis. These results significantly expand the chemical knowledge of C. flava leaves and highlight its potential as a promising source of bioactive saponins and flavonoids.