• Archives of Pharmacal Research
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• v.28 no.4
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• pp.400-404
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• 2005

Activity-guided fractionation of a hexane-soluble extract of the roots of Lithospermum erythrorhizon, using a mouse brain monoamine oxidase (MAO) inhibition assay, led to the isolation of two known naphthoquinones, acetylshikonin and shikonin, and a furylhydroquinone, shikonofuran E. These compounds were shown to inhibit MAO with $IC_{50}$ values of 10.0, 13.3, and $59.1 {\mu}M$, respectively. Although no specificity for MAO-A and MAO-B was shown by acetylshikonin and shikonin, a Lineweaver-Burk plot analysis indicated that the inhibition was competitive for both MAO-A and MAO-B activity.

• Archives of Pharmacal Research
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• v.10 no.2
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• pp.142-147
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• 1987

Fourteen kinds of medicinal plants were screened for determining inhibitory activities on monoamine oxidase B. The extracts of Artemisia Messer-Schmidtiana (herba), Chrysanthemum indicum(flos), Ericibe obtusifolia (radix et rhizoma) and Sophora japonica (flos) strongly inhibited the enzyme. Among them, Chrysanthemi flos was chosen for elucidating its active principles, and some flavonoids were isolated and identified as acasetin (I), 5, 7-dihydroxy chromone (II), diosmetin (III), apigenin (IV), eriodictyol (V) and luteolin (VI).$IC_{50} were determined as following: 1, 2.46;II, 0.19; III, 2. 11mM, and the others showed weak inhibition.

• YAKHAK HOEJI
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• v.46 no.6
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• pp.433-440
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• 2002

The protective efficacy of Rheum palmatum water extract on 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP)-induced parkinsonism was studied in C57BL/6 mice. In order to demonstrate neuroprotective effect of R. palmatum extract, animals were administered intraperitoneally with the water extract (100 or 200 mg/kg/day) for 14 days, and MPTP (10 mg/kg/day) was injected subcutaneously into the mice for the first 6 consecutive days from the beginning 1 hr before R. palmatum extract treatment. All animals were measured the several neurobiochemical markers such as dopamine level and monoamine oxidase B (MAO-B) activity in various regions of brain. The treatment of mice with R. palmatum extract was confirmed recovery effect on MAO-B activity in the cerebellum and the cerebral cortex. R. palmatum extract was attenuated the MPTP-induced depletion of substantia nigra dopamine. The contents of MDA, a marker of lipid peroxidation, in brain tissues (cerebellum and cerebral cortex mitochondria) were decreased significantly by R. palmatum extract. These results suggest that R. palmatum water extract plays an effective role in attenuating MPTP-induced neurotoxicity in mice. This protective effect of R. palmatum might be estimated the result from the inhibitory activity on monoamine oxidase B and the enhancement of antioxidant activity.

• Archives of Pharmacal Research
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• v.24 no.1
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• pp.51-54
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• 2001

Three varieties of methyl citrate and 1 -methyl malate were isolated from the fruits of Opuntia ficus-indica var. saboten Makino through in vitro bioassay-guided isolation for the inhibition on monoamine oxidase(MAO). The $IC_50$ values for MAO-B of 1-monomethyl citrate, 1,3-dimethy citrate, trimethyl citrate and 1-methyl malate were 0.19, 0.23, 0.61 and 0.25 mM, respectively. However, on MAO-A, their inhibitions showed only marginal activity.

• Biomedical Science Letters
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• v.12 no.2
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• pp.91-97
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• 2006

The effects of intravenous administration of high concentration of taurocholic acid (TCA) on monoamine oxidase (MAO) A and B activities in rat liver mitochondria and microsomes were studied. These liver subcellular organelles and serum MAO activities were determined from the experimental rats with choledocho-caval shunt (CCS). The Michaelis-Menten constants in these hepatic enzymes were also measured. The activities of mitochondrial MAO A and B, and microsomal MAO B as well as their $V_{max}$ values were found to be decreased significantly in CCS plus TCA injected group then in the control group, such as CCS alone groups. However their $K_m$ values in the experimental groups did not vary. MAO of serum appeared in the CCS plus TCA injected groups only. The above results suggest that TCA represses biosynthesis of the MAO in the liver. The MAO of serum is believed to be caused by the increment of membrane permeability of hepatocytes upon TCA mediated liver cell necrosis.

• Journal of Applied Biological Chemistry
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• v.61 no.2
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• pp.187-190
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• 2018

Two curcumin derivatives, demethoxycurcumin (DMC) and bisdemethoxycurcumin (BDMC), isolated from Curcuma longa were analyzed for their inhibitory activities against two isoforms of monoamine oxidase (MAO), which is involved in the catalysis of neurotransmitting monoamines. In the study, DMC and BDMC potently inhibited human MAO-B, with $IC_{50}$ values of 2.45 and $2.59{\mu}M$, respectively, and both compounds showed effective inhibitory activities against human MAO-A, with $IC_{50}$ values of 3.24 and $3.09{\mu}M$, respectively. The inhibitory activities of the two compounds were higher than those of curcumin. The removal of the methoxy or dimethoxy groups in curcumin might increase the inhibitory activities against human MAO-A and MAO-B. The inhibited activities were recovered to almost the values of the reversible references in the dialysis experiments with DMC and BDMC. DMC and BDMC showed competitive inhibition for MAO-A and MAO-B, respectively, with $K_i$ values of 0.91 and $0.80{\mu}M$, respectively. These results suggest that the two curcumin derivatives may be useful or lead compounds in the treatment of related disorders as potent reversible MAO inhibitors.

• Journal of Microbiology and Biotechnology
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• v.25 no.9
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• pp.1425-1428
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• 2015

Monoamine oxidase (MAO) is found in most cell types and catalyzes the oxidation of monoamines. Three anithiactins (A-C, modified 2-phenylthiazoles) isolated from Streptomyces sp. were tested for inhibitory activity of two isoforms, MAO-A and MAO-B. Anithiactin A was effective and selective for the inhibition of MAO-A, with an IC₅₀ value of 13.0 μM; however, it was not effective for the inhibition of MAO-B. Anithiactins B and C were weaker inhibitors for MAO-A and MAO-B. Anithiactin A was a reversible and competitive inhibitor for MAO-A with a K_i value of 1.84 μM. The hydrophobic methyl substituent in anithiactin A may play an important role in the inhibition of MAO-A. It is suggested that anithiactin A is a selective reversible inhibitor for MAO-A, with moderate potency, and can be considered a new potential lead compound for further development of novel reversible inhibitors for MAO-A.

• Korean Journal of Pharmacognosy
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• v.37 no.4 s.147
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• pp.229-234
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• 2006

We examined the inhibitory activities against monoamine oxidase (MAO) of Taraxacum mongolicum in vitro and in vivo methods. Methanol extract of T. mongolicum showed significantly inhibitory activities on MAO-A and MAOB that were prepared from rat brain and liver in vitro. MAO-A and MAO-B activities were potently inhibited by chloroform fraction of T. mongolicum in vitro tests. The $IC_{50}$ values of each fraction on MAO-A are as followed; methanol extracts (0.90 mg/ml), $CHCl_3$ fraction (0.10 mg/ml), EtOAc fraction (0.36 mg/ml). and those on MAO-B are methanol extracts $(0.39{\mu}g/ml)$, $CHCl_3$ fraction $(0.18{\mu}g/ml)$, BuOH fraction $(0.22{\mu}g/ml)$. Those MAO-A and MAO-B activities in vivo tests have different tendency each other. MAO-A activity was increased by the oral administration of ethanol extract of T mon golicum, while MAO-B activity was decreased. The concentration of serotonin of brain tissue after oral administration of ethanolic extract of T. mongolicum is slightly increased in rat. This tendency is not different from the activity of deprenyl which is the well known MAO inhibitor used as a positive control. Based on these results, we can suggest that T. mongolicum may have the effects on the inhibitory activities against MAO. Thess activities of T. mongolicum is considerable for development of functional materials for the purpose of treatment and control of depressant, dementia, Parkinson' disease, stress and promoting exercise.

• The Korean Journal of Pharmacology
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• v.20 no.2
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• pp.73-80
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• 1984

The effect of higenamine and its derivatives on the activity of rat bran mitochondrial monoamine oxidase(MAO) was studied. Methoxyhigenamine of drugs tested had no effect on isometric contraction of heart and reversibly inhibited MAO towards 5-hydroxytryptamine(5-HT) and phenylethylamine(PEA) in a pure competitive fashion and in a hyperbolic mixed fashion, respectively, but was found to be relatively MAO-A selective inhibitor, with IC50 value for 5-HT lower ten fold than for PEA. The results suggest that methoxyhigenamine is a reversible, relatively MAO-A specific inhibitor in virto.

• Journal of Microbiology and Biotechnology
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• v.27 no.4
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• pp.785-790
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• 2017

Two piloquinone derivatives isolated from Streptomyces sp. CNQ-027 were tested for the inhibitory activities of two isoforms of monoamine oxidase (MAO), which catalyzes monoamine neurotransmitters. The piloquinone 4,7-dihydroxy-3-methyl-2-(4-methyl-1-oxopentyl)-6H-dibenzo[b,d]pyran-6-one (1) was found to be a highly potent inhibitor of human MAO-B, with an $IC_{50}$ value of $1.21{\mu}M$; in addition, it was found to be highly effective against MAO-A, with an $IC_{50}$ value of $6.47{\mu}M$. Compound 1 was selective, but not extremely so, for MAO-B compared with MAO-A, with a selectivity index value of 5.35. Compound 1,8-dihydroxy-2-methyl-3-(4-methyl-1-oxopentyl)-9,10-phenanthrenedione (2) was moderately effective for the inhibition of MAO-B ($IC_{50}=14.50{\mu}M$) but not for MAO-A ($IC_{50}$ > $80{\mu}M$). There was no time-dependency in inhibition of MAO-A or -B by compound 1, and the MAO-A and -B activities were almost completely recovered in the dilution experiments with an excess amount of compound 1. Compound 1 showed competitive inhibition for MAO-A and -B, with $K_i$ values of 0.573 and $0.248{\mu}M$, respectively. These results suggest that piloquinones from a microbial source could be potent reversible MAO inhibitors and may be useful lead compounds for developing MAO enzyme inhibitors to treat related disorders, such as depression, Parkinson's disease, and Alzheimer's disease.