Quantitative HPLC method and alternative green solvents for extraction of [6]-gingerol from ginger.

A simple and validated HPLC method for quantitative analysis of [6]-gingerol in ginger extracts was established. The optimum HPLC conditions involved a TSK-gel ODS-80 Ts column (5 μm, 4.6 ´ 250 mm) eluted with acetonitrile and 1% aqueous acetic acid (48:52, v/v), at 30ºC, with a flow rate of 1 mL/min and a quantitative UV detection at 280 nm. A good selectivity, linearity (R² of 1.0000), accuracy (Recovery of 96.7-103.2%), intraday- and interday-precision (Relative standard deviation (RSD) of less than 2% and 5%, respectively) and sensitivity (LOD and LOD of 0.48 and 0.80 μg/mL, respectively) were obtained. A microwave-assisted extraction was used for preparation of [6]-gingerol enriched ginger extracts. Based on HPLC analysis, the concentrations of [6]-gingerol of the extracts obtained from 20% v/v glycerin in ethanol (0.45 mg/mL) as well as 20% v/v natural deep eutectic solvents (NADES) of sucrose & citric acid in ethanol (0.43 mg/mL) were not significantly different from ethanol (0.42 mg/mL). However, glycerin (20% v/v) or NADES of sucrose & citric acid (20% v/v) might be used as the alternative green solvents for preparation of [6]-gingerol extract that could be directly used for formulation of anti-nausea and vomiting pastilles.