Comparing the effect of benzoic acid and cinnamic acid hydroxyl derivatives on polyphenol oxidase: activity, action mechanism, and molecular docking

Abstract

BACKGROUND: Polyphenol oxidase (PPO) is considered to have a key role in the food industry because it initiates enzymatic browning in the processing and storage of fruit and vegetables. Increasing numbers of benzoic and cinnamic acid derivatives have been found to be efficient inhibitors of polyphenol oxidase, but a comparison study on activity and action mechanism is lacking. In this study, 18 benzoic acid and cinnamic acid hydroxy derivatives were selected and investigated. RESULTS: Three substrates, four activators and 11 inhibitors were identified from benzoic and cinnamic acid derivatives. 2,4-Dihydroxy-cinnamic acid and benzoic acid showed the strongest inhibitory effect on PPO, with IC 50 of 0.092 and1.425 mmol L −1 , respectively. Benzoic acid reversibly inhibited PPO in a competitive manner, while 2,4-dihydroxycinnamic acid showed a mixed-type inhibition. Both of them showed that static-type fluorescence quenching and electrostatic interaction were the main driving force in the bonding process. Compared with benzoic acid, 2,4-dihydroxycinnamic acid more easily formed hydrogen bonds in the active site of PPO, making the interaction more stable. CONCLUSION: Comparative analysis showed that the inhibition effect of cinnamic acid hydroxyl derivatives on PPO was stronger than that of benzoic acid derivatives. Benzoic acid and 2,4-dihydroxycinnamic acid were the strongest inhibitors. PPO inhibitors identified from benzoic and cinnamic acid derivatives are expected to be promising inhibitors for controlling fruit and vegetable browning.

Purification and Biochemical Characterization of Polyphenol Oxidase Extracted from Wheat Bran (Wan grano)

“…These findings suggested that the obtained, purified wheat PPO had substrate-binding sites with a high affinity for o-diphenolic (e.g., catechol and caffeic acid) and triphenolic (e.g., gallic acid and pyrogallic acid) structures. In contrast to previous reports, protocatechuic acid showed a lower affinity for wheat PPO, despite its o-diphenolic structure [ 18 ]. The phenolic compounds in green tea were more likely to become the substrate of wheat PPO because of their polyhydroxy structure, especially epigallocatechin gallate (EGCG).…”

From polyphenol to o‐quinone: Occurrence, significance, and intervention strategies in foods and health implications

“…However, CQA is a good substrate for PPO and tends to be oxidized to be CQAQ to induce browning. Sun et al (2022) also found that 3,4,5trihydroxybenzoic acid was a PPO inhibitor rather than a substrate. Further research is required to uncover this contradiction.…”

“…Sun et al. (2022) also found that 3,4,5‐trihydroxybenzoic acid was a PPO inhibitor rather than a substrate. Further research is required to uncover this contradiction.…”

“…They are mostly competitive inhibitors, which can occupy the catalytic center of enzymes due to their similar structures to phenolic substrates, thus blocking the entry of substrates. The effects of benzoic acid and cinnamic acid hydroxyl derivatives on PPO activity were compared (Sun et al., 2022). The results indicated that benzoic acid and cinnamic acid hydroxyl derivatives containing catechol or pyrogallol, besides 2,3‐dihydroxybenzoic acid and 3,4,5‐trihydroxybenzoic acid, are PPO‐substrates, whereas some monophenols or m ‐phenols are PPO inhibitors.…”