Effects of drying methods on the active ingredient content and biological activities of pomegranate peels: An investigation of the potential mechanism of polyphenols as antifungal agents

This study investigated the effects of shade drying (SD), hot air drying (HD), vacuum drying (VD), and vacuum freeze-drying (VFD) on the drying characteristics, bioactive compound content, and biological activities of pomegranate peel. Additionally, preliminary research was conducted on the antimicrobial mechanisms of pomegranate peel polyphenols. The results demonstrated that VFD achieved the shortest drying time while maintaining superior appearance quality and the highest levels of bioactive compounds: total phenolic content (TPC, 86.78 mg/g), total flavonoid content (TFC, 19.37 mg/g), total tannin content (TTC, 7.6 mg/g), total anthocyanin content (TAC, 0.07 mg/g), and ABTS antioxidant capacity (383.10 mg TE/g). The VFD treatment also showed superior •OH radical scavenging activity (122.50 mg TE/g) and α-ALA inhibition (5.18 mg/mL), as well as maximum inhibition zones against S. aureus (21.33 ± 0.04 mm), B. subtilis (16.23 ± 0.04 mm), and A. tenuissima (83.89%). The HD demonstrated slightly lower but comparable quality parameters to VFD. 22 major phenolic compounds were identified in the VFD. Molecular docking studies revealed four compounds, including punicalagin, punicalin, rutin, and ellagic acid 4-O-xylopyranoside, that effectively bound to fungal cell wall functional proteins. Among these, punicalagin exhibited primary interactions through hydrogen bonding and hydrophobic interactions with the target proteins.