An insight into chayote (Sechium edule) peels valorization: phytochemical characterization and bioactive potential

Chayote (Sechium edule) is an underutilized Cucurbitacea in Portugal, presenting an interesting nutritional and phytochemical composition. The application of green-extraction techniques to recover valuable bioactive compounds and further investigation on the phytochemical profile of chayote peels is required to promote its sustainable use in food, cosmetic and pharmaceutical sectors.

This study aimed to determine the optimal ultrasound-assisted extraction (UAE) conditions for recovering carotenoids, phenolic compounds, and antioxidant capacity from chayote peel. A response surface methodology using the Box-Behnken design was employed to investigate the impact of ethanol percentage, extraction time, temperature, and ultrasonic power on the recovery of total carotenoid and antioxidant capacity. Chayote peel extracts were also prepared by maceration (ME) and microwave-assisted extraction (MAE) using the same time and temperature conditions optimized by UAE.

Results showed that 37% ethanol, 55 °C and 224 W, for 30 min were the optimal UAE to maximize the recovery of total phenolics (406 mg GAE/100 g DW) and antioxidant compounds (FRAP value of 82.83 mg AAE/100 g DW and ABTS value of 319 mg AAE/100 g DW). The extraction of carotenoids from chayote peel (38 mg/100 g DW) was maximised using 75% ethanol, 35 °C and 168 W, for 30 min. At the same temperature and time conditions, UAE showed greater extraction efficiency of total phenolics and carotenoids than ME and MAE. The HPLC analysis of the extracts showed that tocopherol esters were the main class of carotenoids, followed by retinol esters and a-tocopherol. Moreover, 26 compounds were also identified in the chayote peel extracts by HPLC analysis; the phenolic acids (mostly represented by 4-hydroxyphenilacetic acid, ferulic acid, gallic acid and protocatechuic acid) accounted for 71% of the total compounds quantified, followed by 21% of flavonols (mostly represented by myricetin).

This study reveals the potential of UAE as an effective green extraction technique to recover bioactive compounds from chayote peel, for food, pharmaceutical and cosmetic applications.