Researchers Develop Innovative Strategy for Countercurrent Chromatography Separation of Sanshools From Zanthoxylum bungeanum Oleoresin

Researchers at Beijing Technology and Business University have made significant progress in the field of countercurrent chromatography by developing a general separation strategy. The study, published in the Journal of Separation Science, focused on the separation of sanshools from Zanthoxylum bungeanum oleoresin, a plant known for its rich amide compounds (1).

Formamide (methanamide) solvent molecule | Image Credit: © molekuul.be - stock.adobe.com

Countercurrent chromatography is a liquid-liquid chromatographic technique that utilizes the partitioning of solutes between two immiscible liquid phases for separation. Unlike traditional chromatographic methods, countercurrent chromatography does not require a solid stationary phase. Instead, it employs two liquid phases, typically an organic solvent and an aqueous solution, which flow in opposite directions. This counterflow creates a stationary phase through the equilibrium distribution of solutes between the two phases. The technique offers advantages such as high resolution, low sample loss, and the ability to separate compounds with similar chemical properties. Countercurrent chromatography has found applications in various fields, including pharmaceuticals, natural product research, and biochemistry, for the purification and isolation of complex mixtures.

Sanshools are a series of amide compounds extracted from Zanthoxylum bungeanum, which possess various potential pharmacological properties. However, due to their similar structures, polarities, and dissociation constants, achieving their complete separation through countercurrent chromatography presented a considerable challenge. To overcome this hurdle, the researchers proposed a solvent-system-selection strategy to identify an appropriate solvent system for efficient separation.

The team successfully established a separation procedure that incorporated multi-elution modes selection. Through careful experimentation, they determined that a solvent system consisting of n-hexane, ethyl acetate, methanol, and water in a ratio of 19:1:1:5.67 yielded the best results. Using the recycling elution mode, the researchers obtained high-purity sanshool compounds from the crude extract. Specifically, hydroxy-ε-sanshool (8.4 mg; purity: 90.64%), hydroxy-α-sanshool (326.4 mg; purity: 98.96%), and hydroxy-β-sanshool (71.8 mg; purity: 98.26%) were successfully separated from a 600 mg sanshool crude extract.

The developed solvent-system-selection strategy and separation procedure provide valuable guidance for countercurrent chromatography users, particularly those dealing with compounds that possess highly similar chemical properties. This breakthrough not only opens doors for the separation and purification of sanshool compounds from Zanthoxylum bungeanum oleoresin but also offers a general approach that can be applied to other challenging separations in the field of chromatography.

Countercurrent chromatography, with its ability to achieve high-resolution separation and purification, continues to be a promising technique in the field of analytical chemistry. The findings of this study contribute to the advancement of countercurrent chromatography methodologies and have the potential to benefit various industries, including pharmaceuticals, natural product research, and biochemistry, by facilitating the isolation and characterization of valuable compounds from complex mixtures.

Reference

(1) Han, T.; Ling, T.; Fu, Z.; Cao, X. Development of a general separation strategy by countercurrent chromatography using sanshools from Zanthoxylum bungeanum oleoresin as a case study. J. Sep. Sci. 2023. DOI: https://doi.org/10.1002/jssc.202300115