Ultrasound-Assisted Extraction of L-Tryptophan from Chamomile Flower: Method Development and Application for Flower Parts Characterization and Varietal Difference

Chamomile has been widely used as a functional tea due to its effects on several neurohormones, some of which are related to tryptophan. An analytical ultrasound-assisted extraction (UAE) technique was successfully optimized and validated to determine tryptophan levels in chamomile flowers. A Box-Behnken design,in conjunction with response surface methodology,was conducted based on 3factors and 3levels: Temperature (x1; 30, 50, and 70 °C), solvent composition (x2; 0, 40, and 80% methanol in water), and ultrasonic power (x3; 20, 60, and 100%). The main (x2) and quadratic effect of solvent (x2x2); quadratic of temperature (x1x1) and ultrasonic power (x3x3); also, the interaction of solvent-ultrasonic power (x2x3) and temperature-ultrasonic power (x1x3), significantly affected (p<0.05) the level of L-tryptophan in the extracts. Optimum extraction conditionswere achieved by applying a temperature of 54 °C for 15 min using 17% methanol in water and 69% ultrasonic power. A high recovery (94.26%) was achieved with2extraction cycles. The coefficient of variation (CV) demonstrated that the developed method had a satisfactory level of precision (CV<5%) for repeatability and intermediate precision. To check the applicability of the method, the parts of 2types of chamomile flowers (German and Roman) were evaluated. This method was successfully applied to characterize chamomile flowers based on L-tryptophanlevels.