Ultrasound assisted extraction of gallic acid from Ficus auriculata leaves using green solvent

Gallic acid is a well-known antioxidant ascribed to various beneficial health effects and is found in a variety of plants. In this study, gallic acid was extracted from Ficus auriculata leaves using ultrasound assisted extraction and the process parameters were optimized. The influence of time (5–60 min), temperature (30–75 °C), sonication level (30–70%) and solid to solvent ratio (1:5–1: 40 g/mL) on gallic acid extraction was investigated. Maximum extraction was obtained after 30 min at 50% sonication level, 1:10 g/mL solid to solvent ratio, 8 pH at 50 °C. Among the various solvents, 50% methanol resulted in highest extraction followed by alkaline water and 50% ethanol where gallic acid content in the extract was found to be 329.46 mg/L, 284.16 mg/L and 183.74 mg/L, respectively. Sonication bath was found to perform better in extracting and retaining extracted gallic acid as compared to probe sonication. The kinetics of the extraction was studied and Peleg model was found to have the best correlation with highest R2 value (0.99). The extracted gallic acid was purified using reverse osmosis and HPLC. Results of the present study indicated that ultrasound assisted extraction using alkaline water can be an efficient method for extracting gallic acid from F. auriculata leaves without using harmful organic solvents. This paper will be instrumental to the readers for gaining in-depth comprehension on the water based gallic acid extraction from plant leaves under sonication.