Use of Innovative (Micro)Extraction Techniques to Characterise Harpagophytum procumbens Root and its Commercial Food Supplements

INTRODUCTION: For the determination of harpagoside and the wide phenolic pattern in Harpagophytum procumbens root and its commercial food supplements, dispersive liquid-liquid microextraction (DLLME), ultrasound-assisted DLLME (UA-DLLME), and sugaring-out liquid-liquid extraction (SULLE) were tested and compared. OBJECTIVES: In order to optimise the extraction efficiency, DLLME and UA-DLLME were performed in different solvents (water and aqueous solutions of glucose, β-cyclodextrin, (2-hydroxypropyl)-β-cyclodextrin, sodium chloride, natural deep eutectic solvent, and ionic liquid). MATERIAL AND METHODS: The plant material was ground and sieved to obtain a uniform granulometry before extraction. Commercial food supplements, containing H. procumbens are commercially available in Italy. RESULTS: The most effective sodium chloride-aided-DLLME was then optimised and applied for analyses followed by HPLC-PDA. For comparison, microwave-assisted extraction was performed using the same solvents and the best results were obtained using 1% of β-cyclodextrin or 15% of sodium chloride. CONCLUSION: All commercial samples respected the European Pharmacopoeia monograph for this plant material, showing a harpagoside content ≥ 1.2%.