Inhibitory effects of flavonoids from Hypericum perforatum on nitric oxide synthase

Journal of Ethnopharmacology
L LuoR X Tan

Abstract

The inhibitory effects of six flavonoids from Hypericum perforatum were assessed spectrophotometrically using nitric oxide synthase (NOS) in blood and cerebral homogenate of rats. Of the assayed compounds, quercetin and hyperoside showed concentration-dependent enzyme inhibitory actions. The IC50 values of quercetin for inhibiting NOS in rat cerebral homogenate and blood were 63.06 and 57.54 microM, and those of hyperoside 56.23 and 158.49 microM, respectively. The competitive patterns were discerned with the inhibition of the two flavonoids on NOS in serum and cerebral homogenate (except a mixed type inhibition was observed with quercetin in inhibiting cerebral NOS). Furthermore, similar inhibitions were found for quercetin upon NOS in cerebral homogenate and blood. However, a stronger inhibitory effect of hyperoside on the enzyme was discerned in cerebrum than in blood. These results suggested that the galactose moiety in hyperoside may be associated with the selectivity of the NOS inhibition.

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Citations

Apr 17, 2008·Journal of Natural Medicines·Rawiwun KaewamatawongHiromitsu Takayama
Mar 25, 2011·Journal of Natural Products·Jun-Ho ChoiSun-Mee Lee
Feb 13, 2008·Natural Product Research·Cüneyt CirakBurhan Arslan
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Mar 20, 2008·Phytotherapy Research : PTR·Tayfun I Uzbay
Dec 23, 2006·Journal of Radiation Research·Seyed Jalal HosseinimehrShahram Akhlaghpoor

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