Ultrasound-assisted extraction of phenolic compounds and antioxidant activities from Raphia farinifera Fruit: Box-Behnken design optimization and microstructural characterization

Raphia farinifera fruits are used locally, but their bioactive compounds are poorly studied. This study optimized the use of ultrasound in extraction of phenolic compounds, flavonoids and antioxidant activities from fruit, pulp and kernel extracts of Raphia farinifera by a 4-factor Box-Behnken design (time, sonication temperature, ethanol percentage, and liquid/solid ratio). Subsequently, the impact of ultrasonic treatment on the morphology of the different matrices was carried out. The results showed that the nature of the Raphia farinifera fruit greatly influenced the different responses. In a multi-response optimization, phenolic compound content, flavonoid content, free radical scavenging activity and FRAP were respectively 10.10 mg GAE/g DM, 6.58 mg QE/g DM, 74.07% and 2821.19 µmol TE/L for the pulp, 47.22 mg GAE/g DM, 10.11 mg QE/g DM, 91.69% and 1396.99 µmol TE/L for the shell and 69.58 mg GAE/g DM, 33.24 mg QE/g DM, 99.63% and 1198.65 µmol TE/L for the Kernel. Scanning electron microscopy showed that ultrasonic treatment modified the surface appearance of plant matrices, revealing pores that facilitated solvent penetration, transferring intercellular matter into the solvent. Raphia farinifera fruit extracts have significant antioxidant properties, with many potential applications in medicine, cosmetics, food preservation and functional foods.