Abstract
This study aimed to optimize the preparation process of crocetin from gardenia fruit via alkaline hydrolysis using Box-Behnken response surface design, and to investigate its antioxidant activity and protective effect against mitochondrial hypoxic damage. Single-factor experiments and response surface methodology were employed to optimize key parameters (reaction time, temperature, and KOH concentration) with comprehensive evaluation indicators of yield and crocetin content. The optimal conditions were determined as: reaction time 20 h, temperature 63 °C, and KOH concentration 11 mol/L. Through two-step purification (alkaline extraction and acid precipitation), crocetin with a purity of 95.28% was obtained, and its structure was confirmed by ¹H-NMR and ¹³C-NMR. In vitro antioxidant assays using three chemiluminescent systems (luminol-DMSO-NaOH, luminol-H₂O₂, and luminol-FeSO₄-H₂O₂) showed that trans-crocetin exhibited stronger scavenging activity against •O₂⁻, H₂O₂, and •OH than ascorbic acid (P < 0.05 or P < 0.001). Forced swimming experiments in rats revealed that crocetin significantly alleviated hypoxia-induced mitochondrial damage in gastrocnemius muscles, as evidenced by reduced cristae fragmentation and improved mitochondrial integrity compared to the hypoxia model group. The study demonstrates that the optimized alkaline hydrolysis process enables efficient, eco-friendly extraction of high-purity crocetin from gardenia fruit. Trans-crocetin derived from gardenia exhibits potent antioxidant properties and protective effects against mitochondrial hypoxic injury, suggesting its potential in treating hypoxia-mediated metabolic diseases and tumors.