Optimization of gallic acid yield from labisia pumila in 25-L mobile pilot scale extractor via ultrasound-assisted extraction

Labisia pumila is one of the herbs that has been widely utilized among Malay women in Malaysia. The aim of this study was to evaluate the performance of the ultrasound-assisted extraction (UAE) in 25 L mobile extractor to extract gallic acid from Labisia pumila leaves. For gallic acid extraction both conventional extraction (control) and UAE at 250 kHz were employed, and water was used as the extraction solvent. Initially a preliminary laboratory scale study was conducted using one-factor-at-a-time (OFAT) approach to finalize the ranges of the independent parameters that affect the extraction of gallic acid. Design Expert version 7.0.0 was employed to screen and optimize the gallic acid yield. The extracts were analyzed for gallic acid using high performance liquid chromatography-diode-array detector (HPLC-DAD). The gallic acid yield and the factors were modeled and validated using factorial design and response surface methodology (RSM) approaches. The factors studied were material-to-solvent ratio, temperature, duty cycle, and extraction time. The screening study revealed that the duty cycle was the most influential factor followed by the extraction time, and therefore these two variables were further optimized. Predictive models were generated using the experimental results and the optimal condition predicted was validated. The experimental values under optimal conditions were consistent with the predicted values with the error value of less than 10 %. The predicted optimal yield of gallic acid was 139.44 ± 0. 712 mg GAE/g dry weight at 60 °C and 50% of duty cycle for 8 h. This study confirmed that the use of CAE in 25 L mobile extractor was more effective than the conventional method as it provided more yield in shorter time at lower temperature