Evaluation of antioxidant and anticancer activities of naphthoquinones‐enriched ethanol extracts from the roots of Onosma hookeri Clarke. var. longiforum Duthie

In this study, the optimal naphthoquinones‐enriched ethanol extract from the roots of Onosma hookeri Clarke. var. longiforum Duthie (OHC‐LD) was obtained under an optimal condition (69% ethanol, material to solution ratio of 27:1 at 60℃ for 59 min) by the ultrasound‐assisted extraction, according to four‐variable three‐level Box–Behnken design‐response surface methodology. The experimental yield of ethanol extract was 42.08 ± 0.65%, and the contents of naphthoquinones reached to 1.07 ± 0.004%. The optimal extract exhibited similar scavenging activity against ABTS (2,2'‐azino‐bis‐3‐ethylbenzthiazoline‐6‐sulfonic acid) radical as BHT(butylated hydroxytoluene) at 1,250 µg/ml, and better DPPH (2,2‐diphenyl‐1‐picrylhydrazyl) scavenging activity than BHT at 250 µg/ml. However, the optimal ethanol extract was not sensitive to MCF‐7 cell line ( IC(50) of 321.849 µg/ml). The results revealed the naphthoquinones‐enriched ethanol extract from the roots of OHC‐LD had could be used as a potential natural antioxidant.