OCT1 (IC50 = 36.8 μM); OCT2 (IC50 = 1852.6 μM)

Monocrotaline is a naturally occurring ligand that has strong anti-tumor action and dose-dependent cytotoxicity. Monocrotaline has been shown to have an IC50 of 24.966 µg/mL and a genotoxicity of 2 times IC50 in vitro when tested on HepG2 cells [2].

A rat model of hypertension can be created via animal modeling with monocrotaline. In rats, MCT results in pulmonary vascular syndrome, which is typified by cor pulmonale, pulmonary hypertension (PH), and proliferative pulmonary vasculitis [3]. Monocrotaline-induced animal models have the advantage of closely resembling several important aspects of human pulmonary arterial hypertension (PAH) in preclinical models, such as vascular remodeling, smooth muscle cell proliferation, endothelial dysfunction, inflammatory cytokine upregulation, and right ventricular failure. [4]. The administration of monocrotaline resulted in alterations to several pathways linked to the pathogenesis of peripheral hemorrhage (PH), such as the stimulation of glycolysis, elevations in markers of proliferation, disturbance of carnitine homeostasis, elevations in biomarkers of inflammation and fibrosis, and glutathione production. decrease[5]. Rats given a single dosage of monocrotaline (60 mg/kg i.p.) have considerably higher pulmonary artery pressure, as well as increased right ventricular hypertrophy and pulmonary artery structural remodeling. Then, astragaloside IV (ASIV) was given for 21 days at doses of 10 and 30 mg/kg/d. By enhancing pulmonary arterial remodeling and inflammation, ASIV can prevent pulmonary hypertension [7]. A rat model of pulmonary arterial hypertension (PAH) is induced by monocrotaline (60 mg/kg; ip; single dose) after 3–4 weeks [7]. In a rat model of left lung resection, monocrotaline (60 mg/kg; i.p.; single dose) exhibited significant antitumor efficacy along with dose-dependent cytotoxicity [9]. 1 N HCl was used to dissolve the monocrotaline, which was then diluted with sterile saline and brought to pH 7.4 using 1 N NaOH [7].

Current study systematically investigated the interaction of two alkaloids, anisodine and monocrotaline, with organic cation transporter OCT1, 2, 3, MATE1 and MATE2-K by using in vitro stably transfected HEK293 cells. Both anisodine and monocrotaline inhibited the OCTs and MATE transporters. The lowest IC50 was 12.9 µmol·L-1 of anisodine on OCT1 and the highest was 1.8 mmol·L-1 of monocrotaline on OCT2. Anisodine was a substrate of OCT2 (Km = 13.3 ± 2.6 µmol·L-1 and Vmax = 286.8 ± 53.6 pmol/mg protein/min). Monocrotaline was determined to be a substrate of both OCT1 (Km = 109.1 ± 17.8 µmol·L-1, Vmax = 576.5 ± 87.5 pmol/mg protein/min) and OCT2 (Km = 64.7 ± 14.8 µmol·L-1, Vmax = 180.7 ± 22.0 pmol/mg protein/min), other than OCT3 and MATE transporters. The results indicated that OCT2 may be important for renal elimination of anisodine and OCT1 was responsible for monocrotaline uptake into liver. However neither MATE1 nor MATE2-K could facilitate transcellular transport of anisodine and monocrotaline. Accumulation of these drugs in the organs with high OCT1 expression (liver) and OCT2 expression (kidney) may be expected[8].

Cell Viability Assay[2]
Cell Types: HepG2 cells
Tested Concentrations: 25, 50, 100 and 200 µg/mL
Incubation Duration: 48 h
Experimental Results: Induced apoptosis rate was dose-dependent.

Astragaloside IV blocks monocrotaline‑induced pulmonary arterial hypertension by improving inflammation and pulmonary artery remodeling[7]
Male Sprague-Dawley rats, 8 weeks old weighing 200-230 g, were obtained from the Animal Center of Qiqihar Medical University. The protocol for the present study was approved by the Qiqihar Medical University Institutional Review Board (no. QMU-AECC-2018-27). The rats were housed in a temperature- and humidity-controlled environment with 12-h light/dark cycles. Food and water were available ad libitum. The experiments conformed to the National Institutes of Health guidelines concerning the care and use of laboratory animals, and all animal procedures were approved by the Animal Care and Use Committee of the Qiqihar Medical University. The rats were randomly assigned to 4 groups (8 rats per group) as follows: The control group, the monocrotaline (MCT) group, the MCT + 10 mg/kg/dahy ASIV (ASIV10) group, and the MCT + 30 mg/kg/day ASIV (ASIV30) group. To establish MCT-induced PAH, the rats were administered a single intraperitoneal injection of MCT (60 mg/kg), while the control group received the same volume of saline. MCT was dissolved in 1 N HCl, diluted in sterile saline and adjusted to pH 7.4 with 1 N NaOH. ASIV was initially dissolved in DMSO as a stock solution and further diluted in saline immediately prior to use; the final DMSO concentration was 0.5%. Within hours of the MCT injection, there were signs of pulmonary vascular endothelial damage, but without an increase in pulmonary artery pressure. By 2 weeks, pulmonary artery pressure began to increase, as previously described. At 2 days following the MCT administration, ASIV or the vehicle (0.5% DMSO in saline) were administered intraperitoneally once a day for 21 days.

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A total of 36 male specific-pathogen free Sprague-Dawley rats (age, 6–8 weeks; weight, 300–350 g) were kept in a conventional room at 22±2°C, a relative humidity of 55±10% and a 12-h light/dark cycle. Rats had access to food and water ad libitum. The rats were divided into the following three equal groups at random: Control group, where rats received no treatment; model group, where rats underwent a left pneumonectomy plus subcutaneous injection of 60 mg/kg monocrotaline (MCT), a natural ligand exhibiting dose-dependent cytotoxicity with potent antineoplastic activity, at 7 days following the procedure; PTX group, where rats underwent the same procedure as those in the model group plus administration of 2 mg/kg PTX via the caudal vein (21) daily for 1 week at 3 weeks following injection of MCT[9].

Absorption, Distribution and Excretion
After sc administration of monocrotaline /in rats/, 50-70% of the dose was found in urine as unchanged monocrotaline... monocrotaline (or metabolite) concentration were highest in the liver, kidney and stomach.
The pyrrolizidine alkaloid monocrotaline has been shown to cause hepatic necrosis and pulmonary hypertension in the rat. To better understand the mechanism of action, tissue distribution and covalent binding studies were conducted at 4 and 24 hr following administration of (14)C monocrotaline (60 mg/kg, 200 microCi/kg, sc). For the 4 hr study, the levels of monocrotaline equivalents were 85, 74, 67, 36, and 8 nmol/g of tissue for RBC, liver, kidney, lung, and plasma, respectively, while the covalent binding levels were 125, 132, 39, 64, 44 pmol/mg of protein for tissues as listed above. The 24 hr tissue distribution levels were 49, 25, 9, 10, 2 nmol/g of tissue for RBC, liver, kidney, lung, and plasma, respectively, while covalent binding was 74, 28, and 55 pmol/mg of protein for liver, kidney, and lung, respectively. We also studied the kinetics of (14)C monocrotaline (60 mg/kg, 10 microCi/kg, iv), which demonstrated rapid elimination of radioactivity with approximately 90% recovery of the injected radioactivity in the urine and bile by 7 hr. The plasma levels of radioactivity dropped from 113 nmol/g of monocrotaline equivalents to 11 nmol/g at 7 hr while RBC levels decreased from 144 to only 81 nmol/g at the same time point. The apparent retention of monocrotaline equivalents in the RBC suggests that this organ may act as the carrier of metabolites from the liver to other organs including the lung and may play a role in the pulmonary toxicity.

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Metabolism / Metabolites
Studies with monocrotaline have confirmed the formation of pyrrolic metabolites by the mixed-function oxidase system of the microsomal fraction of rat liver. Dehydromonocrotaline (monocrotaline pyrrole) is highly cytotoxic, producing pulmonary, cardiac, vascular and hepatic lesions similar to those produced by the parent alkaloid. It is a highly reactive alkylating agent which, on formation within the cell, reacts immediately with cell constituents to give soluble or bound secondary metabolites or hydrolyzes to the dehydroaminoalcohol, dehydroretronecine.
Using microsomes from livers of phenobarbital-pretreated male rats, all 13 alkaloids tested were metabolized to n-oxide and pyrrole formation. The 2 pathways appeared to be independent. Ratio of n-oxide to pyrrolic metabolites varied, depending on type of ester: it was highest for open diester alkaloids and lowest for 12-membered macrocyclic diesters and for monoesters. Monocrotaline was one of those tested.
The comparative metabolism of the pyrrolizidine alkaloid, (14)C monocrotaline, was studied using rat and guinea pig hepatic microsomes. ... Esterase hydrolysis accounted for 92% of the metabolism in the guinea pig; the rat displayed no esterase activity. This result may explain the guinea pig's resistance to pyrrolizidine alkaloid toxicity. Dehydropyrrole was found to be the major pyrrolic metabolite in the guinea pig, although colorimetric analysis indicated multiple pyrrolic moieties in the rat microsomal incubations.
This report demonstrates that an Ehrlich reagent positive metabolite of monocrotaline and senecionine is excreted in the urine of male rats as an N-acetylcysteine conjugate of (+/-)-6,7-dihydro-7-hydroxy-1-hydroxymethyl-5H-pyrrolizine ... This finding suggests that reactive metabolites of pyrrolizidine alkaloids generated in the liver can survive the aqueous environment of the circulatory system as glutathione conjugates or mercapturic acids.
For more Metabolism/Metabolites (Complete) data for MONOCROTALINE (7 total), please visit the HSDB record page.

Interactions
Both SKF 525a and metyrapone protected older rats against monocrotaline-induced right heart and lung hypertrophy. Mixed-function oxidase inhibition was more effective than sulfhydryl replacement in attenuating monocrotaline toxicity. Protection was less in younger rats.
Dietary ethoxyquin protected mice against lethality as well as acute hepatotoxicity of monocrotaline as measured by levels of alanine and aspartate aminotransferases in plasma. Dietary cysteine (1%) also protected mice against the lethality but not the acute hepatotoxicity of the alkaloid. With the exception of ethoxyquin, none of the other feed additives increased liver glutathione levels. Glutathione S-transferase activity was significantly increased by either dietary ethoxyquin or cysteine using chlorodinitrobenzene as substrate. Dietary ethoxyquin produced an increase in hepatic cytochrome p-450 content and increases in the in vitro conversion of monocrotaline to pyrrole metabolites by liver microsomes. Since ethoxyquin protected mice against monocrotaline lethality and hepatotoxicity, despite no reduction in the in vivo activation of monocrotaline, the mechanisms involved are most probably a result of increased detoxication processes partly because of increased liver glutathione levels.
Dietary butylated hydroxyanisole (BHA) at levels of 0.25 and 0.75% protected young female mice against the acute toxicity of monocrotaline. Protective effect was associated with reduced levels of pyrrole metabolites in liver, decreased activity of hepatic aminopyrine demethylase, and reduced rate of in vitro microsomal conversion of monocrotaline to pyrrole metabolites. BHA also increased liver sulfhydryl levels and activity of cytosolic glutathione s-transferase. Dietary cysteine (1%) was less protective than BHA against monocrotaline toxicity. LD50 values of monocrotaline in control and cysteine-fed mice were 259 and 335 mg/kg, respectively.

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Non-Human Toxicity Values
LD50 Rat iv 92 mg/kg
LD50 Mouse ip 259 mg/kg
LD50 Rat oral 66 mg/kg
LD50 Mouse iv 261 mg/kg

[1]. The monocrotaline model of pulmonary hypertension in perspective. Am J Physiol Lung Cell Mol Physiol. 2012 Feb 15;302(4):L363-9.
[2]. Antineoplastic activity of monocrotaline against hepatocellular carcinoma. Anticancer Agents Med Chem. 2014;14(9):1237-48.
[3]. Mechanisms and pathology of monocrotaline pulmonary toxicity. Crit Rev Toxicol. 1992;22(5-6):307-25.
[4]. Exploring the monocrotaline animal model for the study of pulmonary arterial hypertension: A network approach. Pulm Pharmacol Ther. 2015 Dec;35:8-16.
[5]. Metabolic Changes Precede the Development of Pulmonary Hypertension in the Monocrotaline Exposed RatLung. PLoS One. 2016 Mar 3;11(3):e0150480.
[6]. Experimental animal models of pulmonary hypertension: Development and challenges. Animal Model Exp Med. 2022 Sep; 5(3):207-216.
[7]. Astragaloside IV blocks monocrotaline‑induced pulmonary arterial hypertension by improving inflammation and pulmonary artery remodeling. Int J Mol Med. 2021 Feb;47(2):595-606.
[8]. An in vitro study on interaction of anisodine and monocrotaline with organic cation transporters of the SLC22 and SLC47 families. Chin J Nat Med. 2019 Jul;17(7):490-497.
[9]. Effects of paclitaxel intervention on pulmonary vascular remodeling in rats with pulmonary hypertension. Exp Ther Med. 2019 Feb;17(2):1163-1170.

Monocrotaline can cause cancer according to an independent committee of scientific and health experts.
Monocrotaline is a pyrrolizidine alkaloid.
Monocrotaline has been reported in Crotalaria sessiliflora, Crotalaria retusa, and other organisms with data available.
A pyrrolizidine alkaloid and a toxic plant constituent that poisons livestock and humans through the ingestion of contaminated grains and other foods. The alkaloid causes pulmonary artery hypertension, right ventricular hypertrophy, and pathological changes in the pulmonary vasculature. Significant attenuation of the cardiopulmonary changes are noted after oral magnesium treatment.

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Mechanism of Action
The toxicology of monocrotaline is complex, and the mechanisms by which it causes lung injury, pulmonary hypertension, and right heart enlargement have remained elusive. ... Monocrotaline is bioactivated by the liver to a reactive, electrophilic pyrrole that travels via the circulation to the lung, where injury results. When low, iv doses of monocrotaline pyrrole are given to rats, a delay of several days occurs before lung injury and pulmonary hypertension become apparent. Moderate depletion of blood platelets around the time of the onset of lung injury lessens the subsequent development of right ventricular enlargement, suggesting a reduction in the pulmonary hypertensive response to monocrotaline pyrrole. This observation prompted a study of the role of platelet-derived mediators in the cardiopulmonary response to monocrotaline pyrrole. A stable analog of thromboxane A2(TxA2) caused a greater increase in right ventricular pressure in monocrotaline pyrrole treated rats compared to controls, and lungs isolated from monocrotaline pyrrole treated rats produced more TxB2 than those of controls. However, administration of drugs that either inhibited thromboxane synthesis or antagonized the effects of thromboxane did not afford protection from monocrotaline pyrrole in vivo. Serotonin, another vasoactive mediator released by platelets, caused an exaggerated vasoconstrictor response in isolated lungs from rats treated with monocrotaline pyrrole. Moreover, removal and inactivation of circulating serotonin by the pulmonary vasculature was impaired by treatment of rats with monocrotaline pyrrole. However, administration of serotonin receptor antagonists did not attenuate the cardiopulmonary effects of monocrotaline pyrrole in vivo. These results suggest that neither TxA2 nor serotonin is the sole mediator of the pneumotoxicity due to monocrotaline pyrrole. Thus, the mechanism by which platelets are involved in the pathogenesis of the pneumotoxic response to monocrotaline pyrrole remains an unsolved puzzle.
Monocrotaline propagates changes in the contractile response of arterial smooth muscle, changes in smooth muscle Na/K-ATPase activity, release of platelet factors, and decreased serotonin transport by vascular endothelial cells.
Effect of ip administration of monocrotaline on activities of hepatic epoxide hydrolase, and arylhydrocarbon hydroxylase was investigated in young, male long-evans rats. Monocrotaline failed to stimulate epoxide hydrolase while diminishing the activity of glutathione s-transferase, aminopyrine demethylase and AHH. There was no effect in vitro on hepatic drug-metabolizing enzymes studied except for slight stimulation of epoxide hydrolase activity and small reduction of aminopyrine demethylase activity.
... An active metabolite of monocrotaline, dehydromonocrotaline (DHM), alkylates guanines at the N7 position of DNA with a preference for 5'-GG and 5'-GA sequences. In addition, it generates piperidine- and heat-resistant multiple DNA crosslinks, as confirmed by electrophoresis and electron microscopy. On the basis of these findings, we propose that DHM undergoes rapid polymerization to a structure which is able to crosslink several fragments of DNA.

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Therapeutic Uses
/Exptl Ther/ Antitumor effects of 22 pyrrolizidine alkaloids and derivatives were studied in mice with adenocarcinomas 755, l-1210 leukemia or sarcoma 180, rats with im or sc walker 256 carcinomasarcoma and in kb carcinoma cell cultures; 1 compound each was also tested in mice with ascites ehrlich carcinoma and hamsters with plasmacytoma number 1. Significant activity against the solid tumors, by CCNSC standards (58% or more decrease in tumor size), was seen with monocrotaline (NSC-28693) in 3 of the above tumors and in p-1. Monocrotaline n-oxide was without significant activity in any of the systems tested.
/Exptl Ther/ Monocrotaline from crotalaria sessiliflora has been shown to be effective against human skin cancer and cancer of uterine cervix.

C16H23NO6

325.36

325.152

C, 59.07; H, 7.13; N, 4.31; O, 29.50

315-22-0

9415

Prisms from absolute alcohol
Colorless

1.4±0.1 g/cm3

537.3±50.0 °C at 760 mmHg

204ºC (dec.)(lit.)

278.7±30.1 °C

0.0±3.2 mmHg at 25°C

1.586

-0.37

2

7

0

23

575

5

O=C(O[C@]1([H])CCN2[C@]1([H])C(CO3)=CC2)[C@H](C)[C@@](C)(O)[C@@](C)(O)C3=O

QVCMHGGNRFRMAD-XFGHUUIASA-N

InChI=1S/C16H23NO6/c1-9-13(18)23-11-5-7-17-6-4-10(12(11)17)8-22-14(19)16(3,21)15(9,2)20/h4,9,11-12,20-21H,5-8H2,1-3H3/t9-,11+,12+,15+,16-/m0/s1

20-Norcrotalanan-11,15-dione, 14,19-dihydro-12,13-dihydroxy-, (13-alpha,14-alpha)- (9CI)

NSC 28693; NSC-28693; monocrotaline; Crotaline; 315-22-0; Monocrotalin; (-)-Monocrotaline; CHEBI:6980; Retronecine cyclic 2,3-dihydroxy-2,3,4-trimethylglutarate; (13-alpha,14-alpha)-14,19-Dihydro-12,13-dihydroxy-20-norcrotalanan-11,15-dione; NSC28693

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 (e.g. under nitrogen), avoid exposure to moisture and light.

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

1M HCl : 200 mg/mL (~614.70 mM)
DMSO : ~25 mg/mL (~76.84 mM)
H2O : ~2 mg/mL (~6.15 mM)

Solubility in Formulation 1: ≥ 2.5 mg/mL (7.68 mM) (saturation unknown) in 5% DMSO + 40% PEG300 + 5% Tween80 + 50% Saline (add these co-solvents sequentially from left to right, and one by one), clear solution.
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: ≥ 2.5 mg/mL (7.68 mM) (saturation unknown) in 5% DMSO + 95% (20% SBE-β-CD in Saline) (add these co-solvents sequentially from left to right, and one by one), suspension solution.
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 (6.39 mM) 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 4: ≥ 2.08 mg/mL (6.39 mM) 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 5: ≥ 2.08 mg/mL (6.39 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 6: ≥ 0.5 mg/mL (1.54 mM)(saturation unknown) in 1% DMSO 99% Saline (add these co-solvents sequentially from left to right, and one by one), clear solution.

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Solubility in Formulation 7: 4.17 mg/mL (12.82 mM) in PBS (add these co-solvents sequentially from left to right, and one by one), clear solution; with ultrasonication (<60°C).

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Solubility in Formulation 8: 21 mg/mL (64.54 mM) in 20% HP-β-CD in Saline (add these co-solvents sequentially from left to right, and one by one), clear solution; Need ultrasonic and warming and heat to 53°C.
Preparation of saline: Dissolve 0.9 g of sodium chloride in 100 mL ddH₂ O to obtain a clear solution.

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