Ultrasonic-assisted extraction of polyphenolics from Schrebera swietenioides Roxb.: An optimization using response surface methodology

Schrebera swietenioides Roxb is an important medicinal plant used for the treatment of various diseases by the indigenous communities. However, this plant is still underexplored in the modern scientific era. Specifically, the leaves of the plant are reported to contain various medicinal properties such as antioxidant, antimicrobial, anti-inflammatory, and antipyretic activity. Herewith, the present work demonstrates and optimizes the extraction process using an ultrasonic system and comopared the results with conventional extraction methods. Optimization was performed by combining first and second-order polynomial designs at different levels using Plackett Burman and Central-Composite designs. A total of 31 experiments were conducted at different levels, including ultrasonic power (10-40 %), solvent-to-sample ratio (20-50 mL/g), solvent concentration (50-80 %), and HCl normality (0.2-1 N). The findings of the study suggest a significant (p<0.05) influence of extraction parameters on the extraction yield of the response variables, including total phenol (TPC), total flavonoid (TFC), total tannin (TTC), and the antioxidants activity. Further, the predicted values demonstrated good agreement with the experimental values, exhibiting a high (R-2>95%) coefficient of determination and a non-significant lack of fit. At the optimized condition, the experimental values of TPC, TFC, TTC and antioxidants (DPPH, ABTS, FRAP) activity were found near the model predicted values. The HPLC-PDA analysis identified ten polyphenolic compounds, among which rutin hydrate (12.991+0.003 +0.003 mg/g DW), followed by phloridzin (6.660+0.001 +0.001 mg/g DW), and chlorogenic acid (3.380+0.008 +0.008 mg/g DW) were the most prominent compounds. Furthermore, the optimized extract showed effective antibacterial activity against Bacillus subtillis, , Escherichia coli, , Pseudomonas aeruginosa, , and Staphylococcus aureus species. In conclusion, the obtained results indicate that the proposed optimization strategy can be utilized to enhance the yield of polyphenolics from the target species with possibility of its application in therapeutics values.