Ultrasound-assisted extraction, characterization, and bioactivity assessment of polyphenol-rich papaya (Carica papaya) leaf extract for application in plant-based food products

This study aimed to valorise papaya leaves for their potential application as a functional food ingredient by optimizing an ultrasound-assisted extraction (UAE) process using a Box–Behnken design. Optimal conditions (0.5 g sample, 55 mL of 50 % ethanol, 13 min, 90 % amplitude) yielded a lyophilized leaf extract (LLE) with a 34 % yield. The extract showed high total phenolic content (112 ± 9 mg GAE g −1 ) and strong antioxidant activity: 64 ± 4 (FRAP), 102 ± 6 (ABTS), 150 ± 9 (CUPRAC), and 37 ± 3 mg Trolox g −1 (DPPH). HPLC-MS identified bioactive compounds such as succinic acid, ferulic acid, quercetin, and rutin. In general, cytotoxicity assays in HepG2 and Caco-2 cell lines indicated a safety profile of the LLE and their main compounds, according to the stablished regulation limits. LLE was incorporated at 5 wt% into soy and coconut oil-based burgers. This addition maintained pH levels and significantly reduced TBARS values over storage, compared to the control. These results support the use of papaya leaf extract as a safe, antioxidant-rich functional food ingredient with preservative potential. • Optimized UAE (Box–Behnken) achieved a 34 ± 2 % yield of lyophilized papaya leaf extract. • The extract presented strong antioxidant capacity (>3700 mg Trolox/100 g (DPPH)). • HPLC-MS identified succinic acid, ferulic acid, quercetin, and rutin. • Cytotoxicity assays confirmed safety of the extract within regulatory limits. • Incorporation of 5 wt% papaya leaf extract into burgers improve shelf life