Use of innovative (micro)extraction techniques to characterize Harpagophytum procumbens root and its commercial food supplements

Introduction - For the determination of harpagoside and a wide phenolic pattern in H. 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 optimize the extraction efficiency, DLLME and UA-DLLME were performed in different solvents (water and aqueous solutions of glucose, β-cyclodextrin, HP-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 were commercially available in Italy. Results - The most effective NaCl-aided-DLLME was then optimized and applied for analyses following 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%.