Green Solvents to Value Annona muricata L. Leaves as Antioxidants Source: Process Optimization and Potential as a Natural Food Additive

The development of a green route to obtain bioactive compounds is of great interest, contributing to the value of underused matrices such as the Soursop leaves. Deep eutectic solvents (DES) using cholinium chloride as HBA, and alcohols and sugars as HBD, were combined with the ultrasound-assisted solid–liquid extraction (UA-SLE) to obtain bioactive compounds from soursop leaves. The solvent effect, temperature, and time of the process were evaluated. The better process conditions were 45 °C and 2 h considering the total phenolic content (TPC), antioxidant activity of the extracts and process energy cost. Among all evaluated solvents, those composed of glycerol and xylitol as hydrogen bond donors presented the higher extraction indexes. The main compounds on the extracts were rutin and catechin as determined by HPLC-DAD. DES demonstrated a protective effect against the thermal degradation of the bioactive compounds. Lastly, considering the meaningful antioxidant activity of the extracts and the DES protective effect, they were applied as a natural additive in soybean crude oil resulting in a satisfactory preservation of the oil. The DES combined with the ultrasound technique allow the obtaining of natural extracts with antioxidant properties which can be applied as a natural supplement to the food industry.