Optimization of microwave-assisted extraction of phenolic compounds from ginger (Zingiber officinale Rosc.) using response surface methodology

Introduction: Ginger (Zingiber officinale Rosc.) is a common spice and precious herbal plant in Vietnam. It contains many bioactive compounds, especially phenolic compounds useful for human health. Hence, the extraction and application of these compounds in medical technology are necessary. Objective: The goal of this study is to determine the optimal extraction conditions with the assistance of microwave, for instance solvent/material ratio (ml/g), solvent concentration (%, v/v) and extraction time, on the extraction yield of ginger rhizome, such as total polyphenol content (TPC) and antioxidant capacity (AC). Methods: The dried sample was extracted by microwave-assisted extraction (MAE). TPC and AC of received extract were measured by the Folin-Ciocalteu method and phenanthroline assay. The optimization process used response surface methodology (RSM) (Central composite face design, CCF) with major influencing factors including solvent concentration, solvent/material ratio and extraction time. Results: The results showed that the optimal extraction conditions were the ethanol concentration of 60%, ethanol/material ratio of 48.6/1 (ml/g), extraction time of 1 minute. Conclusion: The maximum TPC and AC peaked at 27.89±1.99 mg GAE/g dry matter and 12.24±0.04 mmol Fe/g dry matter (DM) at optimal extraction conditions. Besides, some factors strongly affected the extraction yield and interacted together.