Comprehensive study on the formation mechanism of highly bioactive compounds from Allium hookeri root using subcritical water and their antioxidant and anticancer effects

We report the efficiency of green subcritical water extraction (SWE) for the recovery of bioactive compounds from Allium hookeri root (AHR). The highest extraction yield (88 wt%) and highest contents of bioactive compounds including total phenolic content (29.4 mg of gallic acid equivalent/g of dry AHR), total flavonoid content (30.6 mg of quercetin equivalent/g of dry AHR), ascorbic acid (81 mg/g of dry AHR), and gallic acid (2.8 mg/g of dry AHR), as well as high concentrations of Maillard reaction products (melanoidins), and various rare sugars were achieved at 160 °C for 30 min. The SWE extracts possessed 89.3–91.8 % higher antioxidant activities than those of the Soxhlet water extract. As a result, the SWE extract showed strong anticancer effects against human cancer cells of the HT-1080 (fibrosarcoma) and MDA-MB-231 (breast cancer) cell lines, suggesting the possible application of the AHR extract obtained via SWE in cancer therapy and prevention.