Anti-tyrosinase kinetics and antibacterial process of caffeic acid N-nonyl ester in Chinese Olive (Canarium album) postharvest

Enzymatic browning and bacterial putrefaction are mainly responsible for quality losses of Chinese Olive (Canarium album) postharvest and lead to very short shelf life on average. Screening anti-browning and anti-bacterial agents is important for preservation of Chinese Olive. Caffeic acid N-nonyl ester (C-9) and caffeic acid N- Heptyl ester (C-7) was synthesized as inhibitors of tyrosinase, which is a key enzyme in browning process. The compound of C-9 could inhibit the activity of tyrosinase strongly and its IC50 value was determined to be 37.5 μM, while the compound of C-7 had no inhibitory ability. Kinetic analyses showed that compound of C-9 has been a reversible inhibitory mechanism below 50 μM and been irreversible mechanisms above 50 μM. For the reversible inhibitory mechanism, the values of inhibitory constants (KI and KIS) were determined to be 24.6 and 37.4 μM, respectively. The results of Chinese Olive fruit postharvest showed that the compound of C-9 could effectively anti-browning and anti-bacterial putrefaction. In addition, this compound had strong antibacterial activities against Staphylococcus aureus, Escherichia coli, Bacillus subtilis and Salmonella. Therefore, C-9 could be a potential anti-browning and anti-bacterial reagent.