The effects of ultrasonication on the phytochemicals, antioxidant, and polyphenol oxidase and peroxidase activities in coffee leaves

In the present study, we investigated the impacts of ultrasonic conditions on the phytochemical profiles, anti-oxidant activity, and polyphenol oxidase (PPO) and peroxidase (POD) activities in coffee leaves. Ultrasonic frequency, power, and time, pH, and incubation time affected PPO and POD differently, thus resulting in different ABTS scavenging capacity and phenolic content in coffee leaves. Triple-frequency (20/35/50 kHz) ultrasound significantly (P < 0.05) inhibited trigonelline, caffeine, mangiferin, rutin, chlorogenic acids, anti-oxidant activity, and PPO activity, while the single frequency of 35 kHz increased the phenolics compounds, which was associated with the lowest POD activity. Increasing the incubation time after ultrasonication grad-ually decreased phenolic compounds and antioxidant activities, however, POD activity followed a temporal pattern of first increase and then decrease. Our results showed that PPO and POD were temporally inactivated after ultrasonication, which leading to the continuous decrease of phenolics in coffee leaves.

Automated summary

The study investigated the effects of ultrasonic conditions on the phytochemical profiles, antioxidant activity, and enzymatic activities in coffee leaves. Different ultrasonic parameters led to changes in phenolic content and antioxidant activity in coffee leaves. Temporal patterns were observed in the activities of polyphenol oxidase and peroxidase after ultrasonication, impacting the levels of phenolic compounds.