Phytochemical Profiles and Potential Regulatory Mechanisms of Pitaya Flower Extracts from Flowers Processed by Different Drying Methods under AAPH-Induced Oxidative Stress in Zebrafish

The pitaya flower (Hylocereus undatus, Cactaceae) is rich in polyphenols, flavonoids, and polysaccharides with notable antioxidant and anti-inflammatory properties. This study compared four drying methods─shade drying (SD), hot-air drying (HAD), vacuum drying (VD), and vacuum freeze-drying (FD)─on the retention of bioactive compounds and antioxidant activity. High-performance liquid chromatography (HPLC) analysis quantified phenolics, vitamin E (VE), and carotenoids. Except for SD, the total phenolic content (TPC), VE, and carotenoid contents increased to 1.08–4.46 times those of the fresh samples. Using an AAPH-induced zebrafish oxidative stress model, SD extracts most effectively reduced reactive oxygen species (ROS) levels, FD enhanced superoxide dismutase (SOD) and catalase (CAT) activities, and SD best restored glutathione (GSH) content. RT-qPCR results showed that pitaya flower extract alleviated oxidative stress by modulating inflammatory signaling, inhibiting MAPK activation, and regulating the caspase pathway to protect mitochondria. These findings support the potential of pitaya flowers as a functional food ingredient with antioxidant benefits.