Ultrasound-assisted and subcritical water extraction techniques for maximal recovery of phenolic compounds from raw ginger herbal dust toward in vitro biological activity investigation

This study examined the impact of two green extraction techniques in order to maximize the usage and recovery of phenolic compounds from the by-product of the filter tea industry, the so-called ginger herbal dust. The main phenolic compounds extraction was performed by ultrasound-assisted extraction (UAE) with the sonication amplitude ranging from 20% to 100%, and the subcritical water extraction (SWE), with the temperature ranging from 120 °C to 220 °C. All obtained extracts were characterized in terms of extraction yield, total phenolic content (TPC), and 6-ginerol, 6-shogaol, and 8-ginerol contents using RP-HPLC-DAD. Based on the results, we selected the extract obtained from raw ginger herbal dust using a sonication amplitude of 100% for further biological investigation of the cytotoxic effect on short- and long-term cell viability on liver and pancreatic cancer cells. This extract contained high TPC concentration, and 6-gingerol (44.57 mg/gDE), 8-gingerol (8.62 mg/gDE), and 6-shogaol (6.92 mg/gDE).