Inhibitory effects of flavonoids from Hypericum perforatum on nitric oxide synthase

• Published in: Journal of ethnopharmacology Vol. 93; no. 2; pp. 221 - 225
• Main Authors: Luo, L, Sun, Q, Mao, Y.Y, Lu, Y.H, Tan, R.X
• Format: Journal Article
• Language: English
• Published: Shannon Elsevier Ireland Ltd 01-08-2004; Elsevier
• Subjects: Animals; Biological and medical sciences; Cerebral Cortex - enzymology; Dose-Response Relationship, Drug; Enzyme Inhibitors - administration & dosage; Enzyme Inhibitors - pharmacology; Enzyme Inhibitors - therapeutic use; Flavonoids; Flavonoids - administration & dosage; Flavonoids - pharmacology; Flavonoids - therapeutic use; General pharmacology; Hypericum; Hypericum perforatum; Hyperoside (quercetin 3- O-β- d-galactoside); Medical sciences; Nitric oxide synthase; Nitric Oxide Synthase - antagonists & inhibitors; Nitric Oxide Synthase - blood; Nitric Oxide Synthase - drug effects; Nitric Oxide Synthase - metabolism; Pharmacognosy. Homeopathy. Health food; Pharmacology. Drug treatments; Phytotherapy; Plant Extracts - administration & dosage; Plant Extracts - pharmacology; Plant Extracts - therapeutic use; Plant Stems; Quercetin; Rats; Rats, Sprague-Dawley; Hypericum perforatum; Nitric oxide synthase; Flavonoids; Hyperoside (quercetin 3- O-β- d-galactoside); Quercetin; Enzyme; Pharmacognosy; Guttiferae; Hyperoside (quercetin 3-O-β-D-galactoside); Antioxidant; Flavonoid; Biological activity; Nitric-oxide synthase; Medicinal plant; Polyphenol; Enzymatic activity; Dicotyledones; Angiospermae; Spermatophyta; Oxidoreductases
• ISSN: 0378-8741; 1872-7573
• DOI: 10.1016/j.jep.2004.03.042

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 IC
50 values of quercetin for inhibiting NOS in rat cerebral homogenate and blood were 63.06 and 57.54
μM, and those of hyperoside 56.23 and 158.49
μM, 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.