Studies on Scutellariae Radix; XIII¹. Effects of Various Flavonoids on Arachidonate Metabolism in Leukocytes

Abstract

The effects of various flavonoids [i.e. baicalein, baicalin, wogonin, skullcapflavone II, (2S),2′,5,6′,7-tetrahydroxyflavanone, (2R,3R),2′,3,5,6′,7-pentahydroxyflavanone, and 2′,5,5′,7-tetrahydroxy-6′,8-dimethoxyflavone] isolated from Scutellariae Radix on rat peritoneal polymorphonuclear leukocyte lipoxygenase and cyclooxygenase products were studied. Baicalein (5,6,7-trihydroxyflavone) was found to inhibit the formation of 5-HETE (lipoxygenase product) more strongly than the formation of HHT (cyclooxygenase product); its concentrations for 50% inhibition (IC₅₀) were 7.13 ± 0.767 µM for the formation of 5-HETE and 55.3 ± 16.9 µM for the formation of HHT (cyclooxygenase product). Baicalin (baicalein-7-O-D-glucuronide) also inhibited the formation of 5-HETE, though less strongly, while its compound had no effect on the formation of HHT (cyclooxygenase product) in polymorphonuclear leukocytes. In contrast, (2S),2′,5,6′,7-tetrahydroxyflavanone inhibited the formation of HHT more strongly than the formation of 5-HETE via 5-lipoxygenase pathway; its concentrations for IC₅₀ were 5.63 ± 1.27 µM for the formation of HHT and 670.0 + 85.0 µM for the formation of 5-HETE. Wogonin and (2R,3R),2′,3,5,6′,7-pentahydroxyflavanone also inhibited the formation of HHT; their IC₅₀ values were respectively 14.6 ± 3.51 µM and 50.0 ± 4.04 µM.