Abstract: A rapid and simple microwave-ultrasonic synergistic one-step extraction-derivatization (MUED) method and gas chromatography-mass spectrometry was established for the determination of low content fatty acids (FAs) profile in Ranunculus ternatus Thunb. The critical experimental parameters for MUED method were optimized with response surface methodology by taking the chromatographic peak areas of total FAs as a major response index. The best technological parameters were determined as 5.0 g of Ranunculus ternatus Thunb. powder, 50.0 mL of n-hexane, 500 W of microwave power, 50 ℃ of reaction temperature, 0.30 g of catalyst (KOH), 4.0 mL of derivatization reagent (methanol) and the time of extraction-derivatization of 8 min. The contents of individual FAs were quantified by internal standard method. The results showed that the chromatographic peak areas of the total FAs and the total unsaturated FAs contents obtained with MUED were (3.327±0.023)×107 (n=3) and (13.59±0.30) mg/g (n=3) respectively. They were markedly higher than those obtained by the conventional method which were (2.410±0.036)×107 (n=3) and (12.05±0.34) mg/g (n=3) respectively. The MUED method simplified the complicated sample handling steps, shortened the sample preparation time, reduced the cost of analysis, and improved the extraction and derivatization efficiency of the lipids, especially weakened the oxidization and decomposition of the unsaturated FAs. The simplicity, speed and practicability suggest the proposed method has significant potential for the determination of low content FAs in herbal medicines.

Key words: fatty acids, gas chromatography-mass spectrometry (GC-MS), microwave-ultrasonic synergistic action, Ranunculus ternatus Thunb., response surface methodology, one-step extraction-derivatization