Monoamine oxidase A (MAO-A) and monoamine oxidase B (MAO-B)
- Reversible inhibition Ki towards MAO-A (using 5-hydroxytryptamine as substrate): 15 ± 3 μM [1]
- Reversible inhibition Ki towards MAO-B (using β-phenethylamine as substrate): 1.8 ± 0.20 μM [1]
- Time-dependent inhibition parameters for MAO-A: Ki = 13 ± 5 μM, k2 = 0.20 ± 0.06 min⁻¹, t½ = 5 ± 2 min [1]
- Time-dependent inhibition parameters for MAO-B: Ki = 0.5 ± 0.08 μM, k2 = 0.20 ± 0.03 min⁻¹, t½ = 4 ± 0.6 min [1]

Scaffolds are rescued by pargyline HCl (0.5-2 mM; 24-120 hr; LNCaP-LN3 cells) in a mold- and time-assisted manner [2]. In a quantitatively dependent way, pargyline HCl (0.5-2 mM; 24-48 h; LNCaP) and pargyline HCl (0.5 mM; 24 h; LNCaP-LN3 cells) therapy decreases S phase and enhances G1 phase in cells [2]. LNCaP-LN3 cells treated with 0.5 mM pargyline hydrochloride for 24 hours results in an increase in sterile cells [2]. The administration of 2 mM for 48 hours to LNCaP-LN3 cells results in an upregulation of intracellular caspase-3 and cytochrome c. decrease, although it has no effect on BCL-2 expression alterations [2].

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In reversible inhibition studies, pargyline competitively inhibited the oxidation of β-phenethylamine (substrate for MAO-B) in rat liver mitochondrial fractions, with a Ki value of 1.8 ± 0.20 μM. Double-reciprocal plots showed linear competitive inhibition, and secondary plots of slope versus inhibitor concentration were linear. [1]
- For the inhibition of 5-hydroxytryptamine oxidation (MAO-A activity), pargyline produced an intercept effect in double-reciprocal plots due to residual MAO-B activity towards 5-HT. Assuming this intercept effect resulted from MAO-B activity, the reversible Ki towards MAO-A was calculated to be 15 ± 3 μM. The Vmax of MAO-B towards 5-HT was estimated as 20 ± 3% of total Vmax from the intercepts. [1]
- In time-dependent irreversible inhibition experiments, pargyline inactivated both MAO-A and MAO-B following first-order kinetics. The apparent first-order rate constants (k′) were determined at various inhibitor concentrations, and plots of 1/k′ versus 1/[I] yielded linear relationships, consistent with the Kitz-Wilson model. The calculated k2 values were similar for both enzyme forms (0.20 min⁻¹ for MAO-A and 0.20 min⁻¹ for MAO-B), while the Ki values differed (13 μM for MAO-A, 0.5 μM for MAO-B), indicating that the weak selectivity of pargyline towards MAO-B depends primarily on the difference in reversible binding affinities rather than on the rate of covalent adduct formation. [1]

In unanesthetized spontaneous gradients (SHR), pargyline hydrochloride (10 mg/kg; intravenous) treatment results in a moderate (roughly 20 mmc) but sustained (48 h) contraction reduction, but not in normotensive The middle will not [3]. Arterial pressure is lowered by injecting 200 μg of low-dose pargyline hydrochloride (icv) directly into the brain. The buildup of inhibitory alpha-receptin receptors in the brain appears to be the cause of pargyline hydrochloride's antihypertensive effect in SHR [3].

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In unanesthetized adult spontaneously hypertensive rats (SHR), intravenous administration of pargyline at 10 mg/kg induced a moderate but persistent decrease in systolic blood pressure (approximately 20 mmHg) lasting for more than 48 hours. In contrast, pargyline at the same dose did not significantly lower blood pressure in normotensive Wistar-Kyoto rats (WKR) or Sprague-Dawley rats, except for a slight fall at 2 hours in WKR [3].
- A dose-response study in SHR showed that pargyline at 5 mg/kg iv produced a transient fall in blood pressure, while 1 mg/kg iv was ineffective compared to 10 mg/kg iv [3].
- The fall in blood pressure after pargyline (10 mg/kg iv) in SHR positively correlated with the inhibition of brain MAO activity measured ex vivo using norepinephrine as substrate. A blockade of more than approximately 65% of brain MAO activity appeared necessary before a decline in blood pressure was observed [3].
- Pretreatment of SHR with intracerebroventricular (icv) injection of 6-hydroxydopamine (6-OHDA, two doses of 1.63 μmol icv, 48 h apart) lowered brainstem norepinephrine content by about 70% (from 0.73±0.07 μg/g to 0.18±0.02 μg/g). In these 6-OHDA-pretreated SHR, subsequent pargyline (10 mg/kg iv) failed to produce any significant fall in systolic blood pressure; instead, blood pressure tended to rise slightly [3].
- Central α-adrenoceptor blockade with phentolamine (100 μg icv) either prevented (when given 60 min before) or reversed (when given 30 min after) the hypotensive response to pargyline (10 mg/kg iv) in SHR [3].
- Intracerebroventricular administration of pargyline (200 μg icv) to SHR produced a fall in systolic blood pressure lasting more than 2 hours (mean changes: -14±3 mmHg at 0.25 h, -18±1 mmHg at 2 h) compared to saline-treated controls [3].

MAO activity was measured radiochemically at 30°C and pH 7.2. The reaction mixture contained mitochondrial protein at a concentration of 0.63 mg/ml. Substrates used were 100 μM 5-hydroxytryptamine (for MAO-A) and 20 μM β-phenethylamine (for MAO-B). Product formation was linear with tissue amount and time, ensuring initial rate conditions. Activities were corrected for the extraction efficiency of deaminated metabolites. [1]
- For reversible inhibition experiments, the enzyme reaction was started by adding mitochondrial fractions to a mixture containing substrate and inhibitor. Short incubation times (2 minutes for β-phenethylamine, 4-5 minutes for 5-hydroxytryptamine) were used to avoid significant irreversible inhibition. Double-reciprocal plots (1/v vs 1/[S]) were generated, and Ki values were calculated from secondary plots of slope versus inhibitor concentration. [1]
- For irreversible (time-dependent) inhibition studies, mitochondrial fractions (protein concentration 2.5 mg/ml) were preincubated with various concentrations of pargyline at 30°C. At different time points, 20-μl aliquots were withdrawn and diluted into 380 μl of assay mixture (containing substrate), so that reversible inhibition became negligible due to dilution. The remaining enzyme activity was measured, and the logarithm of percent activity remaining was plotted against preincubation time to obtain the apparent first-order rate constant k′. Then 1/k′ was plotted against 1/[I] to determine k2 (the rate constant for covalent adduct formation) and Ki (the dissociation constant of the reversible complex) according to the equation k′ = k2/(1 + Ki/[I]). [1]

Cell Proliferation Assay[2]
Cell Types: LNCaP- LN3 Cell
Tested Concentrations: 0.5 mM, 1 mM, 1.5 mM or 2 mM
Incubation Duration: 24 hrs (hours), 48 hrs (hours), 72 hrs (hours), 96 hrs (hours) or 120 hrs (hours)
Experimental Results: Time and dose dependent Sexual intercourse inhibits the proliferation of prostate cancer cells.

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Cell cycle analysis [2]
Cell Types: LNCaP-LN3 Cell
Tested Concentrations: 0.5 mM, 2 mM
Incubation Duration: 24 hrs (hours), 48 hrs (hours)
Experimental Results: The proportion of cells in S phase diminished and the proportion of G1 phase increased.

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Apoptosis analysis[2]
Cell Types: LNCaP-LN3 Cell
Tested Concentrations: 0.5 mM
Incubation Duration: 24 hrs (hours)
Experimental Results: Increased apoptotic cells.

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Western Blot Analysis[2]
Cell Types: LNCaP-LN3 Cell
Tested Concentrations: 2 mM
Incubation Duration: 48 hrs (hours)
Experimental Results: Induction of increased cytochrome c and diminished caspase-3.

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Cell proliferation assay: LNCaP-LN3 cells were exposed to pargyline at concentrations of 0, 0.5, 1, 1.5, or 2 mM for 24, 48, 72, 96, or 120 h. After treatment, the culture medium was removed, cells were washed with phosphate buffered saline, and WST-1 reagent was added. Following a 4 h incubation, absorbance was measured using a microplate reader [2].
- Cell cycle analysis: Cells were plated in 10 cm² plates and cultured for 24 h before treatment with pargyline (0.5 mM for 24 h or 48 h; also dose-dependent experiment at 0.5 mM for 24 h). After treatment, cells were harvested with trypsin-EDTA, washed twice with PBS, and stained with a DNA reagent kit. Cell cycle distribution was analyzed by flow cytometry, and percentages of cells in different phases were calculated using software [2].
- Real-time RT-PCR: After exposing LNCaP-LN3 cells to 2 mM pargyline for 6, 12, 24, or 48 h, total RNA was isolated and reverse transcribed into cDNA. Real-time PCR was performed using SYBR-Green master mix with primers for BCL-2, NOXA, and β-actin (internal standard). Gene expression levels were analyzed using the 2^ΔΔCT method [2].
- Apoptosis analysis: Cells were plated at 1×10⁶ cells/cm² in 10 cm² plates and grown for 24 h before treatment with 0.5 mM pargyline for 24 h. After treatment, cells were harvested with trypsin-EDTA, washed twice with PBS, and analyzed using an in situ cell death detection kit (fluorescein) by flow cytometry [2].
- Western blot analysis: After treating cells with 0.5 mM pargyline (for apoptosis analysis) or 2 mM pargyline for 48 h (for protein expression), total protein was extracted using RIPA buffer. Proteins were separated by SDS-PAGE, transferred to PVDF membranes, and incubated overnight at 4°C with antibodies against BCL-2, cytochrome c, caspase-3, or β-actin, followed by HRP-conjugated secondary antibodies. Proteins were visualized with ECL detection reagents [2].

Male Wistar rats weighing 100-150 g were killed by a blow to the head. Livers were rapidly removed, blotted on filter paper, and weighed. All subsequent procedures were performed at 0-4°C. Livers were homogenized (1:5 w/v) in 0.25 M sucrose containing 10 mM potassium phosphate (pH 7.2). The homogenate was centrifuged at 600g for 10 minutes to remove nuclei and cell debris. The supernatant was then centrifuged at 15,000g for 10 minutes to obtain mitochondrial pellets. The pellets were washed once by resuspension in the sucrose-phosphate buffer and recentrifugation at 15,000g for 10 minutes, then resuspended to a protein concentration of 5 mg/ml and stored frozen at -20°C until use. [1]

[1]. The nature of the inhibition of rat liver monoamine oxidase types A and B by the acetylenic inhibitors clorgyline, l-deprenyl and pargyline. Biochem Pharmacol. 1982 Nov 15;31(22):3555-61.

[2]. Effects of the monoamine oxidase inhibitors pargyline and tranylcypromine on cellular proliferation in human prostate cancer cells. Oncol Rep. 2013 Oct;30(4):1587-92.

[3]. Central mediation of the antihypertensive effect of pargyline in spontaneously hypertensive rats. Eur J Pharmacol. 1979 Jul 15;57(1):21-7.

Pargyline is an aromatic amine. Pargyline is a monoamine oxidase inhibitor with antihypertensive effects. Pargyline is a monoamine oxidase (MAO) inhibitor with antidepressant activity. Pargyline selectively inhibits monoamine oxidase type B (MAO B), an enzyme that catalyzes the oxidative deamination and inactivation of certain catecholamines (such as norepinephrine and dopamine) in presynaptic nerve endings. By inhibiting the metabolism of these biogenic amines in the brain, Pargyline increases their concentration and enhances their binding to postsynaptic receptors. Enhanced receptor stimulation may lead to downregulation of central receptors, which may explain Pargyline's antidepressant effect. A monoamine oxidase inhibitor with antihypertensive effects. See also: methylchlorothiazide; Pargyline hydrochloride (note moved to).

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Drug Indications
For the treatment of moderate to severe hypertension.

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Mechanism of Action
Monoamine oxidase inhibitors (MAOIs) work by inhibiting the activity of monoamine oxidase, thereby preventing the breakdown of monoamine neurotransmitters and increasing their bioavailability. There are two isoenzymes of monoamine oxidase, MAO-A and MAO-B. MAO-A preferentially deaminates serotonin, melatonin, adrenaline, and noradrenaline. MAO-B preferentially deaminates phenylethylamine and trace amines. Pargyline works by inhibiting the metabolism of catecholamines and tyramine in presynaptic nerve endings. Catecholamines cause general physiological changes, preparing the body for physical activity (fight-or-flight response). Some typical effects include increased heart rate, blood pressure, blood glucose levels, and a generalized response of the sympathetic nervous system.

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Pargyline is a less selective MAO-B inhibitor compared to l-deprenyl. The reversible Ki values show only an 8-fold selectivity for MAO-B over MAO-A (1.8 μM vs 15 μM). The rates of formation of the covalent enzyme-inhibitor adduct (k2) are similar for both enzyme forms (0.20 min⁻¹). Therefore, the relatively weak selectivity of pargyline depends almost completely on the small difference in affinities for reversible non-covalent binding, unlike clorgyline (where affinity difference dominates) and l-deprenyl (where the rate of irreversible adduct formation contributes significantly to selectivity). [1]
- The study demonstrates that the selectivity of acetylenic MAO inhibitors does not reside solely in either differences in reversible binding affinities or differences in the rates of covalent adduct formation; both factors may be involved to different extents with individual inhibitors. This finding is important for the design of selective MAO inhibitors, as modifying a known selective reversible inhibitor by incorporating a reactive group may not necessarily maintain selectivity. [1]

C11H14CLN

195.69

195.081

306-07-0

Pargyline;555-57-7

4688

White to off-white solid powder

228.4ºC at 760 mmHg

160-163ºC

83.9ºC

2.553

0

1

3

12

159

0

BCXCABRDBBWWGY-UHFFFAOYSA-N

InChI=1S/C11H13N.ClH/c1-3-9-12(2)10-11-7-5-4-6-8-11/h1,4-8H,9-10H2,2H31H

N-benzyl-N-methylprop-2-yn-1-aminehydrochloride

Pargyline Hydrochloride N-benzyl-N-methylprop-2-yn-1-amine hydrochloride Eutonyl-ten N-Methyl-N-propargylbenzylamine hydrochloride Pargyline HCl Pargyline

2934.99.9001

Powder      -20°C    3 years

                     4°C     2 years

In solvent   -80°C    6 months

                  -20°C    1 month

Note: Please store this product in a sealed and protected environment, avoid exposure to moisture.

Room temperature (This product is stable at ambient temperature for a few days during ordinary shipping and time spent in Customs)

DMSO : ~125 mg/mL (~638.77 mM)
H2O : ~100 mg/mL (~511.01 mM)

Solubility in Formulation 1: ≥ 2.08 mg/mL (10.63 mM) (saturation unknown) in 10% DMSO + 40% PEG300 + 5% Tween80 + 45% Saline (add these co-solvents sequentially from left to right, and one by one), clear solution.
For example, if 1 mL of working solution is to be prepared, you can add 100 μL of 20.8 mg/mL clear DMSO stock solution to 400 μL PEG300 and mix evenly; then add 50 μL Tween-80 to the above solution and mix evenly; then add 450 μL normal saline to adjust the volume to 1 mL.
Preparation of saline: Dissolve 0.9 g of sodium chloride in 100 mL ddH₂ O to obtain a clear solution.

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Solubility in Formulation 2: ≥ 2.08 mg/mL (10.63 mM) (saturation unknown) in 10% DMSO + 90% (20% SBE-β-CD in Saline) (add these co-solvents sequentially from left to right, and one by one), clear solution.
For example, if 1 mL of working solution is to be prepared, you can add 100 μL of 20.8 mg/mL clear DMSO stock solution to 900 μL of 20% SBE-β-CD physiological saline solution and mix evenly.
Preparation of 20% SBE-β-CD in Saline (4°C，1 week): Dissolve 2 g SBE-β-CD in 10 mL saline to obtain a clear solution.

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Solubility in Formulation 3: ≥ 2.08 mg/mL (10.63 mM) (saturation unknown) in 10% DMSO + 90% Corn Oil (add these co-solvents sequentially from left to right, and one by one), clear solution.
For example, if 1 mL of working solution is to be prepared, you can add 100 μL of 20.8 mg/mL clear DMSO stock solution to 900 μL of corn oil and mix evenly.

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Solubility in Formulation 4: 25 mg/mL (127.75 mM) in PBS (add these co-solvents sequentially from left to right, and one by one), clear solution; with heating and sonication.

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 (Please use freshly prepared in vivo formulations for optimal results.)