Subcritical water extraction of polyphenolic compounds from Terminalia chebula Retz. fruits

This study investigated subcritical water extraction (SWE) of polyphenolic compounds such as gallic acid (GA), ellagic acid (EA), and corilagin (CG) from Terminalia chebula Retz. The effects of extraction temperatures (120–220 °C) and water flow rates (2–4 ml/min) at the pressure of 4 MPa were examined on the amounts of compounds extracted. In addition, the total phenolic contents and antioxidant activities of the extracts were analyzed and compared to those obtained by hot water extraction and Soxhlet extraction with ethanol at ambient pressure. The amounts of extracted GA and EA increased with an increase in subcritical water temperature up to 180 °C, while the highest amount of CG was recovered at 120 °C. Water volumetric flow rate was found to affect the extraction behavior and the suitable flow rate for extraction of total phenolic compounds was 4 ml/min. Compared to other extraction methods, SWE of T. chebula effectively resulted in considerable amount of phenolic compounds with high antioxidant activity.