AMK is an active metabolite of the neurohormone melatonin .1,2,3,4It is formed from melatoninviathe metabolic intermediate AFMK that is then deformylated by catalase or formamidase.5,6AMK scavenges singlet oxygenin vitrowhen used at a concentration of 200 μM.1It inhibits the epinephrine- and arachidonic acid-induced production of prostaglandin E2and PGD2in ovine seminal vesicle microsomes in a concentration- and time-dependent manner, as well as LPS-induced increases in COX-2 levels in RAW 264.7 macrophages when used at a concentration of 500 μM.2,3AMK (20 mg kg) decreases MPTP-induced increases in lipid peroxidation in the cytosol and mitochondria from substantia nigra and striatum in a mouse model of MPTP-induced Parkinson’s disease.4 1.Schaefer, M., and Hardeland, R.The melatonin metabolite N1-acetyl-5-methoxykynuramine is a potent singlet oxygen scavengerJ. Pineal Res.46(1)49-52(2009) 2.Kelly, R.W., Amato, F., and Seamark, R.F.N-acetyl-5-methoxy kynurenamine, a brain metabolite of melatonin, is a potent inhibitor of prostaglandin biosynthesisBiochem. Biophys. Res. Commun.121(1)372-379(1984) 3.Mayo, J.C., Sainz, R.M., Tan, D.-X., et al.Anti-inflammatory actions of melatonin and its metabolites, N1-acetyl-N2-formyl-5-methoxykynuramine (AFMK) and N1-acetyl-5-methoxykynuramine (AMK), in macrophagesJ. Neuroimmunol.165(1-2)139-149(2005) 4.Tapias, V., Escames, G., López, L.C., et al.Melatonin and its brain metabolite N1-acetyl-5-methoxykynuramine prevent mitochondrial nitric oxide synthase induction in parkinsonian miceJ. Neurosci. Res.87(13)3002-3010(2009) 5.Tan, D.-X., Manchester, L.C., Reiter, R.J., et al.Melatonin directly scavenges hydrogen peroxide: A potentially new metabolic pathway of melatonin biotransformationFree Radic. Biol. Med.29(11)1177-1185(2000) 6.Hirata, F., Hayaishi, O., Tokuyama, T., et al.In vitro and in vivo formation of two new metabolites of melatoninJ. Biol. Chem.249(4)1311-1313(1974)
Eicosapentaenoic acid is an ω-3 fatty acid abundantly available in marine organisms. (±)17(18)-DiHETE is one of the major metabolites produced when eicosapentaenoic acid (EPA) is incubated with various rat tissue homogenates or cynomolgus monkey seminal vesicles. The route of production of (±)17(18)-DiHETE likely proceeds through cytochrome P450-catalyzed epoxidation at the ω-3 double bond followed by conversion to the vicinal diols by epoxide hydrolase. EPA is also metabolized preferentially by Gaeumannomyces graminis to (±)17(18)-DiHETE.
ADS-J1 is an HIV-1 entry inhibitor that potently inhibits seminal amyloid fibrillization and block fibril-mediated enhancement of viral infection. Semen-derived amyloid fibrils, comprising SEVI (semen-derived enhancer of viral infection) fibrils and SEM1 fibrils, may remarkably enhance HIV-1 sexual transmission and are potential targets for the development of an effective microbicide.
Δ17-6-keto Prostaglandin F1α (Δ17-6-keto PGF1α), a cyclooxygenase (COX) metabolite produced from eicosapentaenoic acid (EPA) in a variety of tissues including seminal vesicles, lungs, polymorphonuclear leukocytes, and ocular tissues, alongside other 3-series COX products from EPA such as PGF3α, PGE3, and thromboxane B3, is potentially linked to a lower occurrence of glaucoma in individuals consuming a marine-rich (EPA-rich) diet.
Thromboxane B3 (TXB3), the stable hydrolysis product of TXA3, is synthesized from eicosapentaenoic acid (EPA) through the action of COX and thromboxane synthase enzymes. This compound is biosynthesized in several tissues, including seminal vesicles, lungs, polymorphonuclear leukocytes (PMNL), and ocular tissues.
Prostaglandin H2 (PGH2), initially isolated from the incubation of arachidonic acid with ovine seminal vesicle microsomes, acts as a potent vasoconstrictor. It serves as the precursor for all 2-series prostaglandins (PGs) and thromboxanes (TXs). Moreover, as a TP receptor agonist, PGH2 irreversibly aggregates human platelets at concentrations of 50-100 ng ml.
19(R)-Hydroxylated prostaglandins (PGs) are present at µg ml concentrations in the semen of some mammalian species, notably primates, with the majority being from the PGE series and featuring a 15(S),19(R) hydroxyl stereochemistry. These compounds are also observed in marsupials' seminal plasma, where F-type 1 and 2-series compounds are predominant. The 15(R)-hydroxy epimer represents the inverse or unnatural isomer at C-15 for these 19-hydroxylated PGs. Although the biological function of 19(R)-hydroxylated PGs remains unclear, 19(R)-hydroxylation in the F-series leads to a notable reduction in receptor-mediated biological activity in certain assays.
5(6)-DiHET is a racemic compound synthesized through the action of epoxide hydrolases on 5(6)-EET, encompassing both enantiomeric forms. It serves as a quantitative marker for 5(6)-EET, facilitating its measurement by utilizing the compound's conversion to 5(6)-δ-lactone in solution. Additionally, 5(6)-DiHET activates large-conductance calcium-activated potassium (KCa1.1 BK) channels in rat small coronary artery smooth muscle cells, supporting its biological significance in vascular regulation. It also acts as a substrate for sheep seminal vesicle COX, leading to the in vitro production of 5,6-dihydroxy prostaglandin E1 and F1α metabolites. Notably, its levels diminish in the plasma of rats subjected to a high-fat diet, indicating a potential role in the pathophysiology of hyperlipidemia.