Sample preparation

One- and two-year-old hydroponic ginseng plants were separated as roots and shoots parts, and then washed and lyophilized. Each lyophilizate (40 g) was extracted with 700 mL of 70% methanol at 80 °C for 1 h in a reflux system. The extraction was repeated twice. Total extracts were concentrated using a rotary evaporator (EYELA N-1000 V, Tokyo, Japan) at 60 °C, after which they were lyophilized and ground into powder. The lyophilizates of roots of 4- and 6-year-old soil-cultured ginseng (4YSCG, and 6YSCG, respectively) were prepared using the same processing method and were stored at − 20 °C until used.