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

<i>Camellia oleifera</i> 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 <i>C. oleifera</i> 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 (<b>1</b>-<b>3</b>) and polyphenols (<b>4</b>-<b>9</b>). Compound <b>1</b> showed the strongest DPPH scavenging activity with IC₅₀ of 24.19 ± 0.07 μM. Compound <b>9</b> significantly stimulated HaCaT cell proliferation (169.30 ± 2.17%), while compound <b>2</b> promoted the growth of HFF-1 cells (129.36 ± 2.81%). These results highlight the potential of <i>C. oleifera</i> leaves as a valuable source of bioactive compounds for cosmetic and pharmaceutical applications.