Efficient purification of the diarylheptanoid oregonin from red alder (Alnus rubra) leaves and bark combining aqueous extraction, spray drying and flash-chromatography

摘要

Introduction The diarylheptanoid xyloside oregonin ((5S)-1,7-bis(3,4-dihydroxyphenyl)-5-(beta-d-xylopyranosyloxy)-heptan-3-one) has significant medicinal potential and is found at high concentration in leaves and bark of red alder (Alnus rubra). Objectives To establish inexpensive and easily scaled methods for the extraction and purification of oregonin from timber by-products. Methods We developed a method combining aqueous extraction with spray drying of red alder extract into a powder, thus reducing the need for organic solvents used in traditional Soxhlet extraction or in solvent partitioning. Flash chromatography was utilised to purify oregonin from crude spray-dried alder extract. Results Crude spray-dried alder extract was comprised of an average of 9% of the diarylheptanoid compound oregonin. Less than 10% thermal degradation of oregonin was observed using extraction temperatures between 25 degrees C and 50 degrees C, followed by spray drying. The structure of purified oregonin was validated using high-performance liquid chromatography (HPLC), mass spectrometry (MS), ultraviolet spectroscopy (UV), and nuclear magnetic resonance (NMR). Conclusion The developed method was robust, repeatable, and yielded purified oregonin of greater than > 95% purity (average of 95.8%). Our analysis represents the most complete NMR characterisation of oregonin reported to date.