In vitro antioxidant and anti-inflammatory activities of 1-dehydro-[6]-gingerdione, 6-shogaol, 6-dehydroshogaol and hexahydrocurcumin

Hexahydrocurcumin, 1-dehydro-[6]-gingerdione, 6-dehydroshogaol and 6-shogaol were evaluated for their antioxidant and anti-inflammatory activities in the present study. The relative antioxidant potencies of ginger compounds decreased in similar order of 1-dehydro-[6]-gingerdione, hexahydrocurcumin > 6-shogaol > 6-dehydroshogaol in both 1,1-diphenyl-2-picyrlhydrazyl (DPPH) radical-scavenging and trolox equivalent antioxidant capacity (TEAC) assays. All tested compounds could attenuate lipopolysaccharide (LPS)-elicited increase of prostaglandin E2 (PGE2) in murine macrophages (RAW 264.7) in a concentration-dependent manner but hexahydrocurcumin of 7 μM and 6-shogaol of 7 μM. The strongest inhibitory effect was observed for 6-dehydroshogaol and 6-shogaol at 14 μM with the inhibition of 53.3% and 48.9%, respectively. Furthermore, both 6-dehydroshogaol and 1-dehydro-[6]-gingerdione significantly suppressed the expression of inducible nitric oxide synthase (iNOS) and cyclooxygenase-2 (COX-2) proteins in a concentration-dependent fashion. These results contribute to our theoretical understanding of the potential beneficial effects of consuming ginger as a food and/or dietary supplement.

► Determination of in vitro antioxidant activity of four ginger compounds. ► Their effects on PGE2 release and expression of iNOS and COX-2. ► Hexahydrocurcumin and 1-dehydro-6-gingerdione showed the highest antioxidant capacity. ► 6-Dehydroshogaol and 6-shogaol exhibited the strongest PGE2 inhibition. ► iNOS and COX-2 were suppressed by 6-dehydroshogaol and 1-dehydro-6-gingerdione.