Extraction Process Optimization of Polyphenols in Camellia chekiangoleosa Flowers and Analysis of Key Influencing Factors

Camellia chekiangoleosa is a woody species with ornamental, ecological and economic value. Its flowers are rich in polyphenolic active substances, indicating promising potential for development. However, systematic studies on the extraction and bioactivity of polyphenols from flowers remain limited. This study aims to explore the optimization of the extraction process for polyphenols from C. chekiangoleosa flowers and to investigate how key factors affect the extraction yield. Through single-factor experiments and orthogonal test (L₉(3⁴)), extraction temperature and ratio of solid to liquid were identified as the critical factors influencing the yield with the optimal extraction conditions determined as 70% methanol as the solvent, a solid-to-liquid ratio of 1:40, 30 minutes’ extraction at 60℃, extraction repeated for three times, achieving a polyphenol yield rate of (15.37 ± 0.23)%. Studies on different flower parts, blooming stages and drying methods showed that distributions of polyphenols differentiated obviously in developmental stage. The highest polyphenol content was found in the stamens, which was 1.16 times and 1.82 times higher than that in petals and in sepals, respectively; Half-open flowers exhibited the highest polyphenol content, being 1.15 times that of buds and 1.06 times that of fully open flowers. Vacuum freeze-drying yielded the best extraction efficiency, generated the highest polyphenol yield rate, which was 2.04, 2.95 and 2.02 times higher than those obtained in samples by hot-air drying, shade drying, and microwave drying, respectively. In vitro antioxidant activity evaluation showed that the freeze-dried flower samples possessed the highest antioxidant capacity, with IC₅₀ values of 0.011 57 mg·mL⁻¹ for DPPH radicals and 0.016 19 mg·mL^-1 for ABTS radicals.