Extraction of ursolic acid from Ocimum sanctum by ultrasound: Process intensification and kinetic studies

The present work describes the application of ultrasound for the intensification of ursolic acid (UA) extraction from Ocimum sanctum (OS). The different process parameters such as extraction time, solid to solvent ratio, extraction temperature, ultrasound power and frequency have been optimized based on the maximum extraction yield. The maximum yield 16.47 mg UA/g of OS was obtained at optimum extraction conditions (extraction time 12 min, solid to solvent ratio 1:30, temperature 45 C and frequency of 25 kHz). Effect of 25 kHz and 40 kHz has been observed at different power dissipation. The combined effect of frequency and ultrasound power gives a better extraction yield while temperature has no significant effect on extraction. The yield obtained with ultrasound-assisted extraction (UAE) has been compared with batch and soxhlet extraction of UA. This research clearly shows that the UAE method is quite better than conventional extraction as it effectively reduces the extraction time of UA to just 12 min without deterioration. Further, the kinetics of the extraction is investigated by the Peleg's model. The extraction rate constant, initial extraction rate and equilibrium concentration for all experimental conditions have been predicted. The mathematical model applied showed a good agreement with the experimental results. (c) 2013 Elsevier B.V. All rights reserved.