Ultrasound assisted extraction of polyphenols from Randia monantha: Optimization, characterization and antifungal activity

Randia monantha is an important source of high-value biological compounds (HVBC) due to its interesting content of phenolic compounds. However, the antifungal activity of HVBC in the extract remains unexplored. Thus, ultrasound-assisted extraction (UAE) is a technique respects the sample and achieves high yields. Then, to find the optimal UAE conditions for HVBC extraction, a Box-Behnken design was used. The variables included amplitude (40–60%), time (5–10 min), and ratio sample:solvent (1:10–1:30 g:mL. The response variables were yield, total phenolic content (TPC) and 2,2-azinobis (3-ethylbenzthiazoline sulfonate) radical scavenging activity (ABTS+ RSA). Response surface methodology (RSM) revealed that 60% amplitude, 10 min, and 1:30 ratio, produced the extract with the highest yield (11.05 ± 0.23%), TPC (69.26 ± 1.15 mg Gallic Acid Equivalents/g dry sample) and ABTS+ RSA (219.64 ± 6.99 mg Trolox Equivalents /g dry sample). Optimal ethanolic extract evaluated against Colletotrichum gloeosporioides and Penicillium digitatum showed minimum inhibitory concentrations (MIC) of 17.65 and 20.51 mg/mL, respectively. The important antioxidant activity and phenolic content found in the extract are responsible for the inhibitory effect.