Optimizing conditions for oleanolic acid extraction from Lantana camara roots using response surface methodology

Lantana camara is an ornamental plant used in traditional medicine for the treatment of various diseases. The roots of L. camara is a rich source of oleanolic acid which has shown anti-inflammatory, hepatoprotective, antitumor, antioxidant and anti-hyperlipidemic activity. Optimization of various extraction parameters using response surface methodology (RSM) was performed to assess maximum yield of oleanolic acid from L. camara roots. Plackett–Burman design criterion was applied to identify the significant effects of various extraction parameters such as temperature, time, mean particle size, solvent–solid ratio, solvent composition and number of extraction steps on extraction of oleanolic acid. Among the six variables tested extraction time, mean particle size, solvent–solid ratio and solvent composition were found to have significant effect on oleanolic acid extraction. Optimum levels of the significant variables were determined by using a central composite design. The most suitable condition for extraction of oleanolic acid was found to be a single step extraction at extraction temperature 35 °C, extraction time 55 min, solvent–solid ratio 55:1, mean particle size 0.5 mm and solvent composition 52.5% methanol in a methanol-ethyl acetate mixture. At these optimum extraction parameters, the maximum yield of oleanolic acid obtained experimentally (1.74% dry weight of root) was found to be very close to its predicted value of 1.69% dry weight of root. The mathematical model developed was found to fit well with the experimental data of oleanolic acid extraction.     

Optimization of the ultrasound-assisted extraction of tryptophan and its derivatives from rice (Oryza sativa) grains through a response surface methodology

An analytical ultrasound-assisted extraction (UAE) technique has been optimized and validated for the extraction of tryptophan and its derivatives from rice grains. A Box–Behnken design in conjunction with a response surface methodology based on six factors and three levels was used to evaluate the effects of the studied factors prior to optimizing the UAE conditions. The significant (p < 0.05) response surface models with high coefficients of determination were fitted to the experimental data. The most significant (p < 0.0001) effect is the solvent-to-sample ratio while quadratic effects caused by temperature and solvent-to-sample ratio were of moderate importance (p < 0.05). The optimal UAE conditions were as follows: extraction time of 5 min, ultrasound amplitude of 30%, cycle of 0.7 s⁻¹, extraction temperature of 30 °C, 8% methanol in water as the extraction solvent at pH 3 and a solvent/solid ratio 5:1. The method validation ensured that appropriate values were obtained for the LOD, LOQ, precision and recovery. Furthermore, the method was successfully applied to the analysis of a number of rice samples of different varieties. It was demonstrated that this particular UAE method is an interesting tool for the determination of tryptophan and tryptophan derivatives in rice grain samples.