Some secondary plant metabolites in Desmodium adscendens and their effects on arachidonic acid metabolism.
The effects of three chemically different groups of compounds, (triterpenoid saponins, beta-phenylethylamines and tetrahydroisoquinolines), known to be present in Desmodium adscendens, on plasma membrane ion channel, cytochrome P450 NADPH-dependent oxygenation of arachidonic acid, and production of prostaglandins by the cyclooxygenase enzyme system, are described. The very high-conductance calcium-activated potassium ion channel, which is responsible for the maintenance of tone in smooth muscles, was activated by the saponins. The cytochrome P450 NADPH-dependent monooxygenase reaction, which produces epoxy- and hydroxylated eicosanoids from arachidonic acid metabolism, was inhibited by an analogue of the tetrahydroisoquinoline present in the plant. This analogue also acted as a reductant in the prostaglandin synthesizing system using microsomes from ram seminal vesicles. The same system was activated by the beta-phenylethylamines found in the plant material, with the formation of more prostaglandins, the type being dependent on the amount of cyclooxygenase enzyme used and the presence or absence of coenzyme.
Addy
M E
ME
Department of Biochemistry, University of Ghana, Legon.
D000818:Animals; D016718:Arachidonic Acid / Q000378:metabolism*; D001249:Asthma / Q000188:drug therapy; D002240:Carbohydrate Sequence; D006801:Humans; D066298:In Vitro Techniques; D007546:Isoquinolines / Q000494:pharmacology; D008969:Molecular Sequence Data; D010627:Phenethylamines / Q000494:pharmacology; D010946:Plants, Medicinal / Q000378:metabolism*; D015221:Potassium Channels / Q000187:drug effects; D011453:Prostaglandins / Q000096:biosynthesis; D012503:Saponins / Q000737:chemistry / Q000494:pharmacology
D007546:Isoquinolines; D010627:Phenethylamines; D015221:Potassium Channels; D011453:Prostaglandins; D012503:Saponins; D016718:Arachidonic Acid