Optimization of simultaneous ultrasonic‑assisted extraction of water‑soluble and fat‑soluble characteristic constituents from Forsythiae Fructus Using response surface methodology and high‑performance liquid chromatography

Background: The compounds (+)‑pinoresinol‑β‑glucoside (1) forsythiaside, (2) phillyrin (3) and phillygenin (4) were elucidated to be the characteristic constituents for quality control of Forsythiae Fructus extract by chromatographic fingerprint in 2010 edition of Chinese Pharmacopoeia due to their numerous important pharmacological actions. It is of great interest to extract these medicinally active constituents from Forsythiae Fructus simultaneously. Materials and Methods: In this study, a new ultrasound‑assisted extraction (UAE) method was developed for the simultaneous extraction of biological components 1‑4 in Forsythiae Fructus. The quantitative effects of extraction time, ratio of liquid to solid, extraction temperature, and methanol concentration on yield of these four important biological constituents from Forsythiae Fructus were investigated using response surface methodology with Box‑Behnken design. The compounds 1‑4 extracted by UAE were quantitative analysis by high‑performance liquid chromatography‑photodiode array detect (HPLC‑PAD), and overall desirability (OD), the geometric mean of the contents of four major biological components, was used as a marker to evaluate the extraction efficiency. Results: By solving the regression equation and analyzing 3‑D plots, the optimum condition was at extraction temperature 70°C, time 60 min, ratio of liquid to solid 20, and methanol concentration 76.6%. Under these conditions, extraction yields of compounds 1‑4 were 2.92 mg/g, 52.10 mg/g, 0.90 mg/g and 0.57 mg/g, respectively, which were in good agreement with the predicted OD values. In order to achieve a similar yield as UAE, soxhlet extraction required at least 6 h and maceration extraction required much longer time of 24 h. Established UAE method has been successfully applied to sample preparation for the quality control of Forsythiae Fructus. Additionally, a quadrupole time‑of‑flight mass spectrometry was applied to the structural confirmation of analytes from the complex matrices acquired by UAE. Conclusion: The results indicated that UAE is an effective alternative method for extracting bioactive constituents, which may facilitate a deeper understanding of the extract of active constituents in Forsythiae Fructus from the raw material to its extract for providing the theoretical references.