The effect of the oxidized form of neopterin (NP) on the NADPH-dependent superoxide-generating oxidase (NADPH-oxidase) was investigated in both whole-cell and cell-free activation systems by using peritoneal macrophages of rats which had received an intraperitoneal injection of mineral oil. In the whole-cell system, NP remarkably inhibited the generation of superoxides in macrophages stimulated with phorbol myristate acetate (PMA). NP also showed an significant suppression of the activation of superoxide-generating NADPH-oxidase in the cell-free system using solubilized membranes and sodium dodecyl sulfate (SDS) as a stimulant. The 50%-inhibitory concentration (IC,,) of NP was about 1 PM in both assay systems. In a kinetic study, competitive inhibition of the NADPH-oxidase by NP was observed in the cell-free system with a calculated inhibition constant (4) of 6.50 PM. These findings suggest that NP may play an important role in the suppression of superoxide generation via the inhibition of the NADPH-oxidase in phagocytes.

The in vitro potency of neopterin (NP) as an antloxidant and its in vivo activity to suppress alloxan.induced diabetes were investigated. The reduced form of neopterin,5,6,7,, showed an e~trcmely high supcroxide anion radical scavenging activity in two assay s:,,stems, i,e, xanthine/xanthine oxidase-and macrophage/phorbol myristate acetate (PMA).rcaction systems. NPH-4 also inhibited the oxidation of linoleie acid about as effectively as uric acid. Furthermore, NPH-4 ~md NP effectively suppressed alloxan-induced mouse diabetes. Th~e results suggest that pteridines play an important role as endogenous antioxidants,

The rapid and highly separative ultra high-performance liquid chromatography (UHPLC)-UV method was adopted and validated to investigate the flavonol glycoside compositions in ginkgo leaf products on the Japanese market. The result indicates that certain products contained amounts of flavonol glycosides approximately equivalent to the medicinal product. Additionally, we examined the correlations between the total amount of flavonol glycosides and of terpene lactones in various ginkgo leaf products.

A new HPLC method using charged aerosol detection was developed for the determination of terpene lactones in a Ginkgo leaf extract. The linearity of the standard curves was excellent (r > 0:999). The repeatability of the method was less than 3%, and its reproducibility was less than 5% for each analyte. The limit of detection was between 0.087 and 0.45 g/ml. The developed method was applied to the analysis of terpene lactones in Ginkgo leaf products distributed in the Japanese market. The results suggest that some health food products contained approximately equivalent amounts of terpene lactones to those in the medical product and that the proportion of terpene lactones varied in each health product.