Assessment of free and bound phenolics in the flowers and floral organs of two Camellia species flower and their antioxidant activities

Camellia flowers are an important oil source containing abundant phenolic compounds. The free and bound phenolic, flavonoid, and proanthocyanidin fractions and their antioxidant activity were investigated in Camellia oleifera flowers and Camellia polyodonta flowers, stamens, and petals. Phenolic compounds in C. oleifera were studied using high-resolution liquid chromatography-mass spectrometry, which revealed 85 phenolics, including flavonols > ellagitannins > procyanidins > phenolic acids > flavanone > organic acids. Free fractions contributed more greatly to phenolic content and antioxidant capacity than bound fractions in all samples. The highest total phenolics (138.96 mg GAE/g DW), total flavonoids (423.20 mg RE/g DW), and total proanthocyanidins (61.08 mg PB2E/g DW) were obtained in the C. polyodonta flowers, which also exhibited the highest total antioxidant activity. In terms of individual phenolic components, C. polyodonta possessed the highest content of procyanidin B2, procyanidin B4, procyanidin C1, and epicatechin, while C. oleifera displayed the highest content of flavonoids such as quercitrin and afzelin, particularly in the petals. These results implied that Camellia flowers are important natural sources of active components for use in the food industry.