Optimization of Ultrasound-Assisted Extraction (UAE) for Simultaneous Determination of Individual Phenolic Compounds in 15 Dried Edible Flowers

Abstract

Nowadays, dried edible flowers have become one of the eating habits of a healthy lifestyle. The most common way to consume dried flowers is via infused water (tisane). A number of studies on dried edible flowers have reported antioxidant activities mainly due to their phenolic compounds. This work has developed a new extraction method using ultrasound technology to determine phenolic compounds in 15 widely consumed edible flowers. Several extraction factors including pulse duty cycle (0.2, 0.6, 1.0 s−1), temperature (10, 40, 70 °C), solvent-to-sample ratio (10:1, 20:1, 30:1 mL of solvent g −1 of sample), and solvent composition (0, 25, 50% methanol in water) have been optimized based on a Box–Behnken design coupled with response surface methodology. UPLC-PDA has been employed to quantify 12 major phenolic compounds (2,4,6-trihydroxy benzoic acid, protocatechuic acid, protocatechuic aldehyde, p-hydroxybenzoic acid, caffeic acid, vanillic acid, epicatechin, p-coumaric acid, ferulic acid, quercetin-3-rutinose, iso-ferulic acid, and quercetin-3-glucoside) in the extracts. The optimum extraction conditions for a 1 g sample were 30 mL of solvent (28% methanol in water) at 42 °C with 1.0 s−1 of pulse duty cycle. Based on the kinetic study, the optimal extraction time was 10 min. The method was validated with high precision (CVs of repeatability and intermediate precision were lower than 7%) and high accuracy (recovery higher than 90%). Additionally, the proposed ultrasound-assisted extraction was successfully applied in the determination of phenolic compounds in 15 dried edible flowers.