Chemical Composition and Bioactive Properties of Camellia oleifera C. Abel Leaves

Camellia oleifera C. Abel is an economically important oilseed crop. This study aimed to investigate the chemical composition and bioactive potential of its leaf extracts, an underutilized by-product, for cosmetic and pharmaceutical applications. Extracts of C. oleifera leaves were prepared using three solvents (water, 50% ethanol, 95% ethanol) via ultrasonication. The total polyphenol and flavonoid contents were quantified, and key bioactivities, including antioxidant capacity, tyrosinase inhibition, and effects on cell proliferation, were evaluated. The 50% ethanolic extract exhibited the highest total polyphenol (337.24 ± 1.94 GAE/g extract) and total flavonoid (189.23 ± 1.12 mg RE/g extract) contents. This extract also demonstrated superior antioxidant activity, with an IC50 of 28.10 ± 0.46 μg/mL for DPPH scavenging and an ORAC value of 2651.54 ± 112.41 μmol/g. Nine compounds were isolated and identified, comprising flavonoids (1–3) and polyphenols (4–9). Compound 1 showed the strongest DPPH scavenging activity with IC50 of 24.19 ± 0.07 μM. Compound 9 significantly stimulated HaCaT cell proliferation (169.30 ± 2.17%), while compound 2 promoted the growth of HFF-1 cells (129.36 ± 2.81%). These results highlight the potential of C. oleifera leaves as a valuable source of bioactive compounds for cosmetic and pharmaceutical applications.