Supramolecular Solvent-Based Extraction for Lignan HPLC Analysis in Forsythiae Fructus

A team of researchers from the School of Pharmacy at Shanxi Medical University in Taiyuan, China, has proposed a supramolecular solvent-based dispersive liquid-liquid microextraction for the extraction and determination of lignans in Forsythiae fructus combined with high performance liquid chromatography (HPLC). The results of their study were published in the Journal of Separation Science (1).

side view herb Lianqiao or Forsythiae Fructus or Weeping Forsythia Fruit | Image Credit: © Freer - stock.adobe.com

Dispersive liquid–liquid microextraction based on a supramolecular solvent is a sample preparation technique used to extract and pre-concentrate analytes from complex matrices such as plant extracts or biological fluids. It involves the use of a supramolecular solvent consisting of a surfactant and a co-surfactant that can extract analytes. After extraction, the solvent is separated from the sample matrix by centrifugation and analyzed using HPLC. This method is rapid, cost-effective, and environmentally friendly compared to traditional extraction methods.

Forsythiae fructus, also known as the fruit of Forsythia suspensa, is the common name for a traditional Chinese medicinal herb that has been used for centuries to treat various ailments. It is commonly used in traditional Chinese medicine to treat inflammation, fever, and infections, among other conditions. The fruit is typically harvested in the fall when it has ripened and then dried for later use.

Lignans, a group of naturally occurring compounds with a variety of biological activities, are present in many medicinal plants, including Forsythiae fructus. However, the low concentration of lignans in these plants makes their analysis challenging.

For this study, the researchers synthesized a supramolecular solvent consisting of tetrabutylammonium bromide and n-hexanol and mixed it with the sample solution to extract the analytes by a vortex. After completing the extraction, the extraction phase was separated by centrifugation and collected for HPLC analysis.

Several important extraction variables, such as the type and amount of extraction solvent, pH and salt amount in the sample phase, and extraction time, were optimized for this study. They also studied the synthesis of the supramolecular solvent and characterized its microstructure by transmission electron microscopy (TEM).

Under the optimal conditions, the analytes' enrichment factors were between 6–170 for the proposed procedure. The researchers obtained satisfactory linear ranges (r ≥ 0.99), detection limits (0.025–0.4 ng/mL), precisions (<9.2%), and accuracies (recoveries were between 96.5–104.8%). The method has been successfully applied to the preconcentration of lignans in Forsythiae fructus with simple and rapid operation, low cost, and environmental friendliness.

The proposed method offers a potential alternative to existing methods for the analysis of lignans in medicinal plants. The supramolecular solvent-based dispersive liquid-liquid microextraction has the advantages of simplicity, low cost, and environmental friendliness compared to traditional methods.

The team believes that this study's results could provide a valuable reference for the extraction and analysis of lignans in medicinal plants and contribute to the development of efficient and environmentally friendly analytical methods for natural products.

Reference

(1) Qin, Y.; Wang, R.-Q.; Xing, R.-R.; Yang, L.; Chen, X.; Hu, S.Dispersive liquid-liquid microextraction based on a supramolecular solvent followed by high-performance liquid chromatographic analysis of lignans in Forsythiae Fructus. J. Sep. Sci. 2023, ASAP. DOI: 10.1002/jssc.202200719