(S)-Coclaurine

The root of Coptis chinensis Franch

Effects of d-coclaurine and d-reticuline, benzyltetrahydroisoquinoline alkaloids, on levels of 3,4-dihydroxyphenylacetic acid and homovanillic acid in the mouse striatum.[Pubmed:6141236]

J Pharmacobiodyn. 1983 Oct;6(10):793-6.

An intracerebroventricular injection of d-coclaurine (50 micrograms), a benzyltetrahydroisoquinoline alkaloid extracted from Magnolia salicifolia, produced a slight increase in 3,4-dihydroxyphenylacetic acid level and a significant increase in homovanillic acid level in the mouse striatum. Another alkaloid d-reticuline (200 micrograms) increased only homovanillic acid level. An intracerebroventricular pretreatment with d-coclaurine (50 micrograms) did not antagonize suppressive effect of apomorphine on l-dopa formation produced by gamma-butyrolactone (750 mg/kg i.p.) plus aromatic amino acid decarboxylase inhibitor, NSD-1015 (100 mg/kg i.p.). These results suggest that d-coclaurine blocks postsynaptic but not presynaptic dopamine receptors in the mouse striatum.

Inotropic effects of (+/-)-higenamine and its chemically related components, (+)-R-coclaurine and (+)-S-reticuline, contained in the traditional sino-Japanese medicines "bushi" and "shin-i" in isolated guinea pig papillary muscle.[Pubmed:2724702]

Jpn J Pharmacol. 1989 May;50(1):75-8.

(+/-)-Higenamine (Hig. demethylcoclaurine) is a cardiotonic principle from aconite root. (+)-R-Coclaurine (Coc) and (+)-S-reticuline (Ret) are compounds contained in the dried buds of Magnolia salicifolia MAXIM. All of these alkaloids possess a common chemical structure: tetrahydroisoquinoline. Coc and Ret showed negative inotropic effects in contrast to the positive inotropic effects of Hig in papillary muscles of guinea pigs. Coc and Ret shifted to the right the concentration-contraction curves of Hig. Hig shifted in parallel to the left the Ca2+ curve, and it tended to shift to the left the isoproterenol (Isp)-induced response curve. In contrast, Coc and Ret inhibited the Ca2+ curve and the low concentration range of the Isp-induced curve, and it potentiated the high concentration ranges of Ca2+ and Isp. Coc and Ret showed actions that were reversed in direction to those of Hig, as clearly demonstrated in the Ca2+ curve.

Purification and characterization of coclaurine N-methyltransferase from cultured Coptis japonica cells.[Pubmed:11314949]

Phytochemistry. 2001 Apr;56(7):649-55.

S-Adenosyl-L-methionine (SAM): coclaurine N-methyltransferase (CNMT), which catalyzes the transfer of a methyl group from S-adenosyl-L-methionine to the amino group of the tetrahydrobenzylisoquinoline alkaloid coclaurine. was purified 340-fold from Coptis japonica cells in 1% yield to give an almost homogeneous protein. The purified enzyme, which occurred as a homotetramer with a native Mr of 160 kDa (gel-filtration chromatography) and a subunit Mr of 45 kDa (SDS-polyacrylamide gel electrophoresis), had an optimum pH of 7.0 and a pI of 4.2. Whereas (R)-coclaurine was the best substrate for enzyme activity, Coptis CNMT had broad substrate specificity and no stereospecificity CNMT methylated norlaudanosoline, 6,7-dimethoxyl-1,2,3,4-tetrahydroisoquinoline and 1-methyl-6,7-dihydroxy-1,2,3,4-tetrahydroisoquinoline. The enzyme did not require any metal ion. p-Chloromercuribenzoate and iodoacetamide did not inhibit CNMT activity, but the addition of Co2+, Cu2+ or Mn2+ at 5 mM severely inhibited such activity by 75, 47 and 57%, respectively. The substrate-saturation kinetics of CNMT for norreticuline and SAM were of the typical Michaelis-Menten-type with respective Km values of 0.38 and 0.65 mM.

Coclaurine is a class of tetrahydroisoquinoline alkaloids isolated from Sarcopetalum harveyanum. Coclaurine is a nicotinic acetylcholine receptor (nAChRs) antagonist.

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