6]-Dehydroshogaol, a minor component in ginger rhizome, exhibits quinone reductase inducing and anti-inflammatory activities that rival those of curcumin

Abstract

Quinone reductase (QR) inducing activity, a biomarker for Phase II enzyme induction, was detected in a crude ginger rhizome ethanolic extract using a murine hepatoma cell (Hepa 1c1c7) bioassay. An ethyl acetate-partitioned fraction became enriched in QR inducing activity with a CD value (concentration required to double QR specific activity) of 7 μg/ml and was further separated by silica flash chromatography. The four major fractions recovered exhibited CD values ranging 10–20 μg/mL for QR inducing activity. 1H NMR analysis revealed an abundance of gingerols in the first 3 fractions, and this led to a comparative assessment of QR inducing and anti-inflammatory activities among [6]-gingerol and structurally related vanilloids from ginger and other spices. [6]-Dehydroshogaol (DHSG), a minor component of fresh ginger, had QR inducing activity (CD = 8.4 μM) of comparable potency to the well known cancer preventive agent, curcumin (CD = 4.3 μM). In contrast, [6]-gingerol the major pungent component of ginger showed less potent QR inducing activity (CD = 55 μM) and capsaicin exhibited the weakest inducing activity (CD = 103 μM). [6]-Shogaol, [6]-DHSG and curcumin were also potent inhibitors of nitric oxide (NO) synthesis, inhibiting 50% NO evolution in activated macrophages at levels of 10–12 μM (IC 50 values). Comparatively, IC 50 values for [6]-gingerol and capsaicin were about an order of magnitude greater (less potent) at 90 μM and 169 μM, respectively. This appears to be the first report of biological activities of [6]-DHSG, and Phase II enzyme-inducing ability of shogoal and gingerol.