Identification of kaempferol as a monoamine oxidase inhibitor and potential Neuroprotectant in extracts of Ginkgo biloba leaves

J Pharm Pharmacol. 2000 Apr;52(4):451-9. doi: 10.1211/0022357001774075.


The effects of Ginkgo biloba leaf extract on rat brain or livermonoamine oxidase (MAO)-A and -B activity, biogenic amine concentration in nervous tissue, N-methyl-D-aspartate (NMDA)- and N-(2-chloroethyl)-N-ethyl-2-bromobenzylamine (DSP-4)-induced neurotoxicity and antioxidant activity was investigated to determine the effects of the extract on monoamine catabolism and neuroprotection. Ginkgo biloba leaf extract was shown to produce in-vitro inhibition of rat brain MAO-A and -B. The Ginkgo biloba extract was chromatographed on a reverse-phase HPLC system and two of the components isolated were shown to be MAO inhibitors (MAOIs). These MAOIs were identified by high-resolution mass spectrometry as kaempferol and isorhamnetin. Pure kaempferol and a number of related flavonoids were examined as MAOIs in-vitro. Kaempferol, apigenin and chrysin proved to be potent MAOIs, but produced more pronounced inhibition of MAO-A than MAO-B. IC50 (50% inhibition concentration) values for the ability of these three flavones to inhibit MAO-A were 7 x 10(-7), 1 x 10(-6) and 2 x 10(-6) M, respectively. Ginkgo biloba leaf extract and kaempferol were found to have no effect ex-vivo on rat or mouse brain MAO or on concentrations of dopamine, noradrenaline, 5-hydroxytryptamine and 5-hydroxyindoleacetic acid. Kaempferol was shown to protect against NMDA-induced neuronal toxicity in-vitro in rat cortical cultures, but did not prevent DSP-4-induced noradrenergic neurotoxicity in an in-vivo model. Both Ginkgo biloba extract and kaempferol were demonstrated to be antioxidants in a lipid-peroxidation assay. This data indicates that the MAO-inhibiting activity of Ginkgo biloba extract is primarily due to the presence of kaempferol. Ginkgo biloba extract has properties indicative of potential neuroprotective ability.

MeSH terms

  • 3,4-Dihydroxyphenylacetic Acid / metabolism
  • Administration, Oral
  • Animals
  • Brain / drug effects
  • Brain / enzymology
  • Brain / metabolism
  • Cells, Cultured
  • Chromatography, High Pressure Liquid
  • Dopamine / metabolism
  • Dose-Response Relationship, Drug
  • Flavonoids*
  • Ginkgo biloba / chemistry*
  • Hydroxyindoleacetic Acid / metabolism
  • Kaempferols*
  • Lipid Peroxidation / drug effects
  • Liver / drug effects
  • Liver / enzymology
  • Male
  • Mice
  • Monoamine Oxidase / drug effects
  • Monoamine Oxidase / metabolism
  • Monoamine Oxidase Inhibitors / analysis*
  • Monoamine Oxidase Inhibitors / pharmacology
  • N-Methylaspartate / pharmacology
  • Neurons / cytology
  • Neurons / drug effects
  • Neuroprotective Agents / pharmacology*
  • Norepinephrine / metabolism
  • Plant Extracts / chemistry
  • Plant Extracts / pharmacology*
  • Plant Leaves / chemistry*
  • Plants, Medicinal*
  • Quercetin / analogs & derivatives*
  • Quercetin / analysis
  • Quercetin / pharmacology
  • Rats
  • Rats, Sprague-Dawley
  • Serotonin / metabolism
  • Tumor Cells, Cultured / drug effects
  • Tumor Cells, Cultured / metabolism


  • Flavonoids
  • Kaempferols
  • Monoamine Oxidase Inhibitors
  • Neuroprotective Agents
  • Plant Extracts
  • 3,4-Dihydroxyphenylacetic Acid
  • Serotonin
  • Hydroxyindoleacetic Acid
  • N-Methylaspartate
  • kaempferol
  • Quercetin
  • Monoamine Oxidase
  • Dopamine
  • Norepinephrine