Structural stabilization of mango polyphenol oxidase by sucrose under ultrasonic treatment: Mechanistic insights from spectroscopic and molecular docking analyses

This study investigated the effect of sucrose on the inactivation of mango polyphenol oxidase (PPO) induced by ultrasound (US). After US treatment (20 kHz, 300 W, 9 min, ice-water bath), the relative activity (RA) of mango PPO in the control group was 50.0%. Sucrose significantly (P < 0.05) attenuated US-induced inactivation in a concentration-dependent manner, with RA reaching 72.9% at 16% sucrose. Additionally, molecular docking revealed that sucrose binds near the dinuclear copper active center of PPO, with an interaction energy of 154.17 kcal/mol. Furthermore, spectral analyses demonstrated that sucrose interacts with both the internal hydrophobic core and surface domains of PPO, enhancing its structural stability. Higher sucrose concentrations were found to enhance the structural stability of mango PPO, as evidenced by: (1) increased α-helix content (from 34.09% to 35.22%); (2) decreased random coil content (from 31.39% to 30.97%); and (3) attenuated ultrasound-induced structural perturbation. Fluorescence spectroscopy revealed a significant reduction in intrinsic fluorescence intensity (P < 0.05), suggesting enhanced interaction between sucrose molecules and the hydrophobic core of PPO. These structural modifications collectively contribute to improved molecular stability, thereby increasing PPO's resistance to ultrasound-mediated inactivation. • Sucrose significantly (P < 0.05) protects mango PPO from US inactivation. • Higher sucrose levels progressively reduce US-induced PPO inactivation. • Molecular docking reveals sucrose binds near PPO’s copper-active site. • Sucrose prevents US-induced structural damage to PPO, enhancing stability.