Abstract

Wild Syrian rue (Peganum harmala L. family Zygophyllaceae) is well-known in Iran and various parts of this plant including, its seeds, bark, and root have been used as folk medicine. Recent years of research has demonstrated different pharmacological and therapeutic effects of P. harmala and its active alkaloids, especially harmine and harmaline. Analytical studies on the chemical composition of the plant show that the most important constituents of this plant are beta-carboline alkaloids such as harmalol, harmaline, and harmine. Harmine is the most studied among these naturally occurring alkaloids. In addition to P. harmala (Syrian rue), these beta-carbolines are present in many other plants such as Banisteria caapi and are used for the treatment of different diseases. This article reviews the traditional uses and pharmacological effects of total extract and individual active alkaloids of P. harmala (Syrian rue).
Keywords: Harmine, harmaline, peganum harmala, pharmacological effects, wild syrian rue

INTRODUCTION

Harmal[1] (Peganum harmala L. family Zygophyllaceae) is a perennial, glabrous plant which grows spontaneously in semi-arid conditions, steppe areas and sandy soils, native to eastern Mediterranean region. It is a shrub, 0.3-0.8 m tall with short creeping roots, white flowers and round seed capsules carrying more than 50 seeds. The plant is well-known in Iran and is widely distributed and used as a medicinal plant in Central Asia, North Africa and Middle East.[2,3,4,5] It has also been introduced in America and Australia. Dried capsules – mixed with other ingredients – are burnt as a charm against “the evil eye” among Iranians.[2] This plant is known as “Espand” in Iran, “Harmel” in North Africa and “African rue,” “Mexican rue” or “Turkish rue” in the United States.[6] Various parts of P. harmala including its seeds, fruits, root, and bark, have been used as folk medicine for a long time in Iran and other countries [Table 1]. Many pharmacological surveys have shown different effects of P. harmala [Table 4] and/or its active alkaloids (particularly harmaline) [Table 5].

Studies carried out on the chemical composition of the extracts show that beta-carboline and quinazoline alkaloids are important compounds of this plant [Figure 1]. In one study, the concentration of harmaline in different parts of the plant including seeds, fruits, and capsule walls was determined by Reverse phase high-performance liquid chromatography (RP-HPLC) as 56.0 mg/g, 4.55 mg/g and 0.54 mg/g, respectively.[7] Although, harmaline and harmine are the most important alkaloids that are generally responsible for their beneficial effects, numerous studies show that other alkaloids present in P. harmala also have some roles in the pharmacological effects of the plant.[8] Harmaline (C13H15ON2) was first isolated by Göbel from the seeds and roots of P. harmala and is the major alkaloid of this plant.[6] In addition to P. harmala (Harmal), beta-carboline alkaloids are present in many other plants such as Banisteriopsis caapi (Malpighiaceae). They are also constituents of Ayahuasca, a hallucinogenic beverage ingested in rituals by the Amazonian tribes.[7] This article completely reviews the pharmacological effects of P. harmala [Table 2] and its active ingredients [Table 3].[6,7]

CARDIOVASCULAR EFFECTS

P. harmala is one of the most frequently used medicinal plants to treat hypertension and cardiac disease worldwide.[9,85] It has also been shown in various pharmacological studies that P. harmala extract or its main active alkaloids, harmine, harmaline, Harman and harmalol, have different cardiovascular effects such as bradycardia, decreasing systemic arterial blood pressure and total peripheral vascular resistance, increasing pulse pressure, peak aortic flow and cardiac contractile force,[10] Vasorelaxant[11,12] and angiogenic inhibitory effects.[13]

CARDIOVASCULAR EFFECTS

P. harmala is one of the most frequently used medicinal plants to treat hypertension and cardiac disease worldwide.[9,85] It has also been shown in various pharmacological studies that P. harmala extract or its main active alkaloids, harmine, harmaline, Harman and harmalol, have different cardiovascular effects such as bradycardia, decreasing systemic arterial blood pressure and total peripheral vascular resistance, increasing pulse pressure, peak aortic flow and cardiac contractile force,[10] Vasorelaxant[11,12] and angiogenic inhibitory effects.[13]

Vasorelaxant and antihypertensive effects

The aqueous (AqE) extract of the seeds of P. harmala have antispasmodic, anticholinergic, antihistaminic and antiadrenergic effects.[14] One study on the cardiovascular effects of harmine, harmaline and harmalol indicated that these three alkaloids have vasorelaxant effects with rank order of relaxation potency of harmine >harmaline >harmalol. In case of the first two alkaloids this vasorelaxant activity was not only attributed to their interaction with the alpha 1-adrenergic receptors in vascular smooth muscles but also more importantly to their increasing effect on notric oxide (NO) release from the endothelial cells, which was dependent on the presence of external Ca2+. Harmalol had no effect on the release of NO from the endothelial cells and it weakly interacted with the cardiac 1,4-dihydropyridine binding site of L-type Ca2+ channels (Ki value of 408 microM).[11] In the same study, the vasorelaxant activity of harman, another active alkaloid of P. harmala, was shown with a mechanism of interaction with the L-type Ca2+ channels and increasing NO release from the endothelial cells so dependent on the presence of external Ca2+. These effects of harman may be involved in its hypotensive activity.[15] Another study indicates that the action of harmaline on the prostacyclin pathway also plays a role in its vasoleraxant activity.[12] It has been also shown that harmaline, harmalol and harmine decrease systemic arterial blood pressure and total peripheral vascular resistance obviously not due to activation of cholinergic, beta-adrenergic and histamine (H1) receptors. The harmaline-evoked decreases were frequently followed by a secondary increase and these two effects of harmalol were inconsistent.[10] Astulla et al. also showed in an in vitro study the vasorelaxant activity of vasicinone, another alkaloid isolated from the seeds of P. harmala, against phenylephrine-induced contraction of isolated rat aorta.[16]

Effects on the heart

There have been a few studies conducted regarding the direct effects of P. harmala extract and its alkaloids on heart muscle. For example, in one study it was shown that three P. harmala isolated alkaloids (Harmine, Harmaline and Harmalol) have ionotropic effect and also decrease heart rate in normal anesthetized dogs. Since neither vagotomy nor atropinization affected the harmala-induced bradycardia it became evident that the decrease in heart rate was not due to a negative chronotropic effect of the alkaloids.[10]

In another in vivo study, harman dose-dependently produced transient hypotension and long-lasting bradycardia in anesthetized rats.[11] Harmaline inhibits both 45Ca2+ uptake and efflux in cardiac sarcolemal vesicles in a dose-dependent manner.[17]

Angiogenic inhibitory effect

It was revealed in a study that harmine is a potent angiogenic inhibitor. This substance can significantly decrease the proliferation of vascular endothelial cells and reduce expression of different pro-angiogenic factors such as vascular endothelial growth factor, NO and pro-inflammatory cytokines. Nuclear factor-κB and other transcription factors like cAMP response element-binding (CREB) and Activating transcription factor 2 (ATF-2) involved in angiogenesis were also inhibited by harmine. Moreover, harmine decreased production of other factors by tumor cells, which play a significant role in angiogenesis like cyclooxygenase (COX-2), inducible nitric oxide synthase, and matrix metalloproteases.[13]
Inhibitory effect on platelet aggregation

The alkaloids of P. harmala are also shown to have anti-platelet aggregation effects.[18] However, there is not so much evidence on this effect of the plant so far.
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EFFECTS ON NERVOUS SYSTEM

In traditional medicine, P. harmala has been used among societies to treat some nervous system disorders such as Parkinson's disease,[19] in psychiatric conditions[7] such as nervosity,[20] and to relieve rigorous pain.[21] The alkaloid content of P. harmala is shown to be psychoactive[22] and various in vitro and in vivo studies indicate a wide range of effects produced by P. harmala and its active alkaloids on both central and peripheral nervous system including, analgesia,[22,23] hallucination, excitation,[24] and anti-depressant effect.[25,26]

Some of these alkaloids such as harmaline, harmine, and norharmane are also endogenous compounds present in the body and since they have been found in high plasma concentrations in alcoholics,[27] drug addicts,[28] smokers,[29] and patients with Parkinson's disease,[30] they are thought to be crucially involved in various central nervous system (CNS) problems.

It has been also proven that P. harmala-derived beta-carbolines interact with opioid,[21] dopamine,[24] GABA (Gamma-Aminobutyric acid),[31] 5-hydroxytryptamine, benzodiazepine, and imidazoline[32] receptors present in the nervous system and this way induce their many pharmacological effects. Moreover, these alkaloids are neuroprotective[31,33] and strong inhibitors of monoamine oxidase and this important feature makes them a preferable target in the treatment of some conditions like depression.[25]
Mono amine oxidase inhibition and anti-depressant effect

Beta-carbolines present in P. harmala strongly inhibit monoamine oxidase enzyme that is the main factor in degradation and reuptake of monoamines like serotonin and norepinephrine. It was pointed out in an in vitro study that seed and root extracts of P. harmala significantly inhibits MAO-A but has no effect on MAO-B. In case of the seed extract the inhibitory effect was reversible and competitive with an IC50 of 27 μg/l and it was mostly attributed to harmaline and harmine. The strong inhibitory effect of the root extract was only due to harmine and the IC50 was calculated as159 μg/l.[7] It could be concluded that this inhibitory effect has the potential to reverse the MAO-mediated monoamine reduction in depression. Harmine at high doses increased the BDNF (Brain-derived neurotrophic factor) protein level, which is decreased in depressive conditions, while imipramine, a common anti-depression drug, had no such effect.[25] Farzin et al. revealed in a study on the anti-depressant effects of harmane, norharmane, and harmine using the mouse force swim test that these alkaloids of P. harmala have a significant dose-dependent anti-depressive effect with a suggested mechanism of acting on benzodiazepine receptors. It was shown in another in vitro study that the extract of P. harmala has the ability to inhibit catechol-O-methyltransferase and thereby the methylation of catecholamines with a mixed type mechanism.[34] All of these effects represent an idea that P. harmala and its derivatives could be used for treatment of mood disorders and are potent alternatives for current anti-depression drugs.

Analgesic and antinociceptive effects

The analgesic effect of different forms of P. harmala extract (ethyl acetate [EAE], butanolic [BE], and AqE) have been investigated in various parallel studies. The methods used in these studies include formalin, hot plate, and writhing tests. The results showed that all forms of the extracts produced the analgesic effect. Among the extracts, BE showed the maximum effect with a percentage of 35.12% in the writhing test. In case of the AqE, the nociceptive effect was only observed in the second phase of the formalin test. Treatment with both EAE and BE produced a dose-dependent analgesia. Since treatment with naloxone prevented the nociceptive effect of the extracts, it is concluded that an opioid-modulated mechanism is involved. The results also indicated that the extracts act both centrally and peripherally.[21,23,35]
Relation with Parkinson's disease

The endogenous harmala alkaloids have been proven to be involved in Parkinson's disease.[31] One study on both endogenous and exogenous beta-carbolines showed that they all have general DAT-mediated (Dopamine active transporter-mediated) dopaminergic toxicity and therefore, are involved in the pathogenesis of Parkinson's disease.[36] Adversely, it was revealed in an in vitro study that two of these endogenous compounds, norharman and 9-methylnorharman, have good anti-parkinsonism effects via inhibition of MAO-B, an enzyme involved in the production of parkinsonism-related substances from the neurotoxin 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine. However, naturally occurring beta-carbolines had almost no such inhibitory effect.[33]

In contrast, several studies on the anti-parkinsonism effect of B. caapi revealed that its beta-carboline content (harmine and harmaline) has significant effect against this disease through the inhibition of MAO-B.[37,38] Although, these beta-carbolines with anti-parkinsonism effect are also present in P. harmala, there have been no studies conducted regarding the possible effect of P. harmala isolated alkaloids against Parkinson's disease, thus far.
Other neuropsychological effects

There have been reports of other effects produced by P. harmala in the nervous system.

In an in vitro study desoxypeganine, one of the P. harmala alkaloids, dose-dependently decreased ethanol consumption in female Alko alcohol rats with no effect on food and fluid consumption.[39] This may represent a safe way to decrease the consumption of alcohol in alcoholics. Harmane, another alkaloid isolated from P. harmala induced amnesia with a suggested mechanism of interaction with dopaminic (D1 and D2) receptors.[24] Harmaline and harmane have been shown to modulate voltage-activated calcium- ICa (V)-channels in vitro and in a reversible and use independent manner.[31]
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ANTIMICROBIAL EFFECTS

Various studies have shown different antiparasidal,[16,40] antifungal,[41,42] antibacterial[41,43] and insecticidal[44,45] effects of the alkaloids derived from P. harmala seeds. It has also been used widely as an anti-fungal[42] and antiparasidal[46] agent in traditional medicine of some parts of the world. For instance, in Saudi Arabia it has been so common to use P. harmala against fungal infections.[42] In one study, the methanolic, AqE and chloroform extracts of P. harmala were shown to have respectively strong, moderate, and slight inhibitory effects on the growth of Aspergillus flavus, Aspergillus fumigatus, Aspergillus niger and Candida albicans.[42]

Preparations of P. harmala were also used in folk medicine of South-Eastern Spain as anti-leishmanial remedies.[46] Moreover, its powdered seeds and various extracts have been used as a remedy against tapeworm infections in men and animals in the indigenous system of medicine.[40]
Antiprotozoal effect

Various studies have been carried out investigating in vitro and in vivo effects of different P. harmala extracts on forms of leishmania parasites. One study on the effect of P. harmala extract on Leishmania infantum revealed that harmine and harmaline have weak anti-leishmanial activity against both promastigote and amastigote form of the parasite. At the same time, harmaline showed strong toxicity against the amastigote forms inside the macrophages. The suggested mechanism for this property is the inhibitory effect of harmaline on protein kinase C (PKC) action of the parasites.[47] Another study compared the in vitro antileishmanial activity of antimonyl tartrate and P. harmala extract against L. major. During this study the extract showed the same potency as antimonyl tartrate that means it could be a good alternative for the antimonial drugs as the first-line antileishmanial treatments with lots of severe side effects.[48] The effectiveness of the extract is mostly attributed to its beta-carboline content. P. harmala extract also decreased the lesion size and number of the parasites in cutaneous form of the disease.[49] In addition to the beta-carbolines, peganine another alkaloid of P. harmala, was shown to have strong in vitro and in vivo toxicity against both amastigotes and promastigotes of Leishmania donovani. A dose of 100 mg/kg body weight of peganine was effective against visceral leishmaniasis in hamsters.[50]

There have been several studies indicating effectiveness of P. harmala extract against theileriosis.[51,52] Two studies were conducted in Iran on the effect of P. harmala extract with a dose of 5mg/kg body weight once daily for 5 days on cattle[52] and sheep[51] theileriosis that showed a significant recovery rate of respectively 78% and 65%.

Beta-carbolines from the seeds of P. harmala showed strong trypanosomicidal activity against nifurtimux-resistant LQ strain of Trypanosoma cruzi. Inhibition of respiratory chain appears to be the possible determinant of this action of beta-carbolines.[53]

Furthermore, there have been reports of antiplasmodial activity of different P. harmala alkaloids such as vasicinone, deoxyvasicinone, and beta-carbolines.
Antibacterial activity

One of other important features of P. harmala alkaloids is their bactericidal activity that is comparable with that of common antibiotics, which have many adverse effects. Different species of bacteria have been shown to be susceptible to these alkaloids. For example Proteus vulgaris and Bacillus subtilis appeared to be very sensitive to harmine.[41] The activity of these alkaloids depended on the microorganism and the application method. For instance, the methanolic extract showed higher antibacterial potency against all tested micro-organisms (Staphylococcus aureus, Pseudomonas aeruginosa, Escherichia coli, Klebsiella pneumoniae, and P. vulgaris) than other chloroform and petroleum extracts in one study.[43]

It is concluded that P. harmala and its alkaloids could probably be used for the control of antibiotic resistant isolates of bacteria.[54]
Insecticidal and antifungal activity

In vitro treatment with individual alkaloids of P. harmala or a mixture of them was so efficient against A. niger and C. albicans with a minimal inhibitory concentration of total (crude) alkaloids respectively 0.333 ± 0.007 MIC (Minimum inhibitory concentration) (mg/ml) and 0.333 ± 0.007 MIC (mg/ml).[41] A synergistic activity of different alkaloids present in the crude extract might be involved in its strong effect.

Furthermore, there have been some reports about insecticidal activity of P. harmala-derived beta-carbolines indicating their inhibitory effects on the development and growth of the larval stages of some insects. For example harmaline prevented the development of larvae of Plodia interpunctella, an insect pest of stored food, to the pupal and adult stages.[44] This inhibitory effect of harmaline was due to its severe toxicity on the epithelial cells of the midgut that finally leads to shedding of the cytoplasm contents into the midgut lumen.

Another study showed the insecticidal activity of methanolic P. harmala extract against Tribolium castaneum, the stored grain pest. Larvae growth was significantly inhibited with the incorporation of the extract into their diet. The adult form of the insect was also susceptible. It could be a good idea to use P. harmala as a tool to control the population of such harmful insects.[45]
Antineoplasm, antiproliferative and antioxidant effects

Since ancient times, P. harmala has been used by traditional healers to make various preparations in the treatment of cancers and tumors in some parts of the world.[13,55] For example, it has been so common in traditional medicine of Morocco to use powdered seeds of P. harmala to treat skin and subcutaneous tumors.[56] The seed extract of P. harmala is the main component of a very common ethnobotanical preparation used against different cancers and neoplasms in Iran, namely Spinal-Z.[57,58]

The antitumor activity of P. harmala and its active alkaloids (mainly beta-carbolines) have also drawn attentions of many researchers worldwide that has led to various pharmacological studies regarding this important effect of P. harmala.[23,56] Various authors have reported cytotoxicity of P. harmala on tumor cell lines in vitro and in vivo. In one study, the methanolic extract of P. harmala reduced significantly proliferation of three tested tumor cell lines (UCP-Med (a tumor cell line), Med-mek carcinoma, and UCP-Med sarcoma) in all concentrations. This anti-proliferative effect was produced by the alkaloid fraction of the extract in the first 24 h of the treatment. A cell lysis effect was observed in the next 24 h and thus, resulted in complete cell death within 48 to 72 h.[56] The same results were observed with the total extract of the plant in another study. The extract also showed cytotoxicity against artificially grafted subcutaneous Sp2/O cell-line in BALB-c (Albino) mice.[56] Administration of different beta-carboline alkaloids isolated from P. harmala showed inhibitory effect against Lewis Lung cancer sarcoma-180 or HepA tumor in mice at rates of 15.3-49.5%. Substitution of formate at R3 and aryl at R9 of the tricyclic skeleton respectively decreased neurotoxicity and increased the inhibitory effects of the alkaloids that made them ideal agents to be used as novel antitumor drugs with lesser side effects.[55] Several in vitro and in vivo studies have revealed that these cytotoxicity and antitumor effects of P. harmala are related to its interaction with RNA,[59] DNA and its synthesis,[56,60] and inhibition of human Topoisomerase.[58] In a study conducted in Iran, it was shown using the DNA relaxation assay that the extract of P. harmala inhibits human DNA Topoisomerase I. This effect was attributed to the beta-carboline content of the extract and potency of the alkaloids were determined as harmine >harmane >harmaline in a way that treatment with the total extract showed weaker inhibitory effect than treatment with every individual alkaloid.[58] Another study indicated that harmine and its derivatives have inhibitory effect on human Topoisomerase I activity but no effect on Topoisomerase II. Intercalation of several carbolines into eukaryotic DNA has also been reported by many authors.[58,61] This intraction of beta-carbolines cause significant structural changes in DNA and interfere with its synthesis.[56,61] The alkaloid-DNA binding affinity was ordered as harmine >harmalol >harmaline >harmane >tryptoline. There are also other suggested mechanisms for the anti-tumor activity of P. harmala alkaloids. In an in vitro study by Li et al., budding yeast was used as a model to investigate the anti-tumor activity of P. harmala. Results showed that DH334, a beta-carboline derivative and an anticancer drug, specifically inhibits cyclin dependent kinases (CDKs) and blocks the initiation of cell cycle at the G1 phase. It also inhibited the kinase activity of Cdk2/CyclinA (a member of the cyclin family) in vitro. This could be another possible mechanism for the antitumor activity of the drug.[56,93]

Many pharmacological studies suggest an antioxidant and free radical scavenging effect of P. harmala. This effect has been attributed to the increasing effect of P. harmala extract on E2 (17β-estradiol) level as an important antioxidant and reactive oxygen species (ROS) scavenger.[12,62,63] In another study, the effects of harmaline and harmalol were tested on Digoxin-induced cytochrome P450 1A1 (CYP1A1), a carcinogen-activating enzyme, in human hepatoma HepG2 cells. These alkaloids significantly inhibited the enzyme via both transcriptional and posttranslational mechanisms in a concentration-dependent manner.[3] Ethanol and chloroform extracts of P. harmala showed protective effects against thiourea-induced carcinogenicity by normalization of neuron-specific enolase and thyroglobulin levels in animal models.[64] Other effects of the plant extract such as anti-proliferative effect on Leukemic cell lines,[65] inhibitory action on the metastasis of melanoma cells, inducing apoptosis in melanoma cells,[66] tumor angiogenesis inhibition,[13] and binding to RNA[61] have also been reported by various authors. In some cases, P. harmala showed a higher selectivity towards malignant cells than common anticancer drugs like doxorubicin.[57] All of these data suggest that P. harmala and its alkaloids possess the potential to be used as novel antioxidant and anti-tumor agents in anti-cancer therapy.
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INDUCING EMMENAGOGUE AND ABORTION

P. harmala has been used traditionally as an effective emmenagogue and abortificient agent in the Middle East, India, and North Africa.[6,56,67] It has also been shown that abortion happens frequently among animals that digest this plant in a dry year.[8,68] Quinazoline alkaloids (e.g., vasicine and vasicinone) within P. harmala have been attributed to the abortificient effect of this plant.[8]
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GASTROINTESTINAL EFFECTS

P. harmala extract and powdered seeds have been used in folk medicine of different parts of the world to treat colic in man and animals.[40] The efficiency of this plant in treatment of colic is due to its antispasmodic effect[69] probably as a result of blocking different types of intestinal calcium channels[70] by the alkaloid content of the plant specially harmaline. P. harmala also possesses noticeable nauseant[71] and emetic[7,72] effects.
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OSTEOGENIC ACTIVITY

Two different studies conducted by Yonezawa et al. showed bone anabolic effects of harmine, in vivo and in vitro.[73,74] It was revealed that administration of 10 mg/kg/day of harmine inhibits formation and differentiation of osteoclasts in mice via down-regulation of c-Fos (A cellular proto-oncogene) and NFATc1 (Nuclear factor of activated T-cells, cytoplasmic 1) and thus, prevents osteoclast-mediated resorption. Adversly, it enhances osteoblast differentiation probably via inducing the expression of BMPs and activation of bone morphogenetic protein (BMP) and Runx2 pathways. It was also found that carbon C3C4 double-bond and 7-methoxy group of harmine plays an important role in these processes. These findings suggest that harmine, as the main alkaloid of P. harmala, may be useful for treatment of some bone diseases.
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IMMUNE SYSTEM EFFECTS

Beta-carboline alkaloids of P. harmala are shown to have immune-modulatory effects in several studies.[26,75] Extracts of this plant have significant anti-inflammatory effect via the inhibition of some inflammatory mediators including prostaglandin E2 (PGE2) (100 μg/mg) and tumor necrosis factor alpha (TNF-α) (10 μg/mg).[46]
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ANTIDIABETIC EFFECTS

P. harmala has been traditionally used to treat diabetes in folk medicine of some parts of the world.[69,76] This effect of P. harmala has been pharmacologically confirmed in several studies one of which showed that the plant would lose its hypoglycemic activity at high doses instead of increasing it.[77] Harmine is the main alkaloid of P. harmala that is involved in its anti-diabetic effect.[25] One study shows that harmine regulates the expression of peroxisome proliferator-activated receptor gamma (PPARγ), the main regulator of adipogenesis and the molecular target of the thiazolidinedione antidiabetic drugs, through inhibition of the Wnt signaling pathway. Therefore, it mimics the effects of PPARg ligands on adipocyte gene expression and insulin sensitivity without showing the side-effects of thiazolidinedione drugs such as weight gain.[78]
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TOXICITY

In addition to all therapeutic effects of P. harmala, there have been several reports of human[79] and animal[68] intoxications induced by this plant. There are also experimental studies indicating P. harmala toxicity.[6,7] In an in vitro study, intrapretoneal administration of three different extracts of P. harmala at a dose of 50 mg/kg body weight induced sympthoms such as: Abdominal writhing, body tremors and slight decrease in locomotor activity,[21] while oral administration of these extracts showed no toxicity. There have been also the same symptoms reported in different human cases[2,6,80] following ingestions of P. haramala seed extract or infusion including: Neuro-sensorial symptoms, visual hallucination, slight elevation of body temperature, cardio-vascular disorder such as bradycardia and low blood pressure, psychomotor agitation, diffuse tremors, ataxia and vomiting. Despite animal intoxications in almost all of human cases, P. harmala poisonings were relieved in a few hours.[6] P. harmala extract is toxic at high-doses[7,77,81,82] and can cause paralysis, liver degeneration, spongiform changes in the central nervous system,[83] euphoria, convulsions, digestive problems (nausea, vomiting), hypothermia and bradycardia.[2,6,68,80] However, therapeutic doses have been reported to be safe in a rodent model.[54]

MAO inhibition activity of P. harmala components are the main cause for the toxicological effects after ingestion of the plant.[7] Moreover, the intercalation of P. harmala alkaloids into DNA has led to its mutagenic property which causes genotoxic effects.[84] P. harmala methanolic extract has showed teratogenic effects in female rats.[68] The extract prolonged diestrus phase, reduced number of living pups, and decreased the number of resorption. It also dose-dependantly decreased litter size.[8] These data all together suggest that care should be taken while using P. harmala and its derivatives as therapeutic agents in order to prevent probable intoxications.
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DRUG INTERACTION

P. harmala is shown to interact with drug metabolism due to its significant effects on the expression of cytochrome P450s (CYP), the most important superfamily of drug metabolizing enzymes. Seeds of this plant dose-dependently increase the expression of CYP1A2, 2C19, and 3A4 whereas decrease the expression of CYP2B6, 2D6 and 2E1. Harmine and harmaline are the main contents involved. These data all together suggest that care should be taken when P. harmala is co-administered with other drugs.[3]
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CONCLUSION

Our aim in preparing this paper was to show the traditional usage and previously confirmed pharmacological effects of P. harmala as one of the most well-known medicinal plants in Iran and to illustrate it's potential to be used as a novel source for the development of new drugs based on the most recent associated studies. As it is evident from this study, P. harmala has a wide range of pharmacological effects including cardiovascular, nervous system, gastrointestinal, antimicrobial, antidiabetic, osteogenic, immunomodulatory, emmenagogue, and antitumor activity among many other effects. Beta-carboline alkaloids contained in P. harmala are the most important contents of the plant responsible for most of its pharmacological effects. Since there have been many reports of intoxications following ingestion of specific amounts of P. harmala seeds, care should be taken by scientists and clinicians regarding usage of this plant for therapeutic purposes until adequate studies confirm the safety and quality of the plant. Finally, based on this information, this review provides the evidence for other researchers to introduce P. harmala as a safe and effective therapeutic source in the future.
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Footnotes

Source of Support: Nil

Conflict of Interest: None declared

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Some of these alkaloids such as harmaline, harmine, and norharmane are also endogenous compounds present in the body and since they have been found in high plasma concentrations in (...) drug addicts,[28] smokers,[29] and patients with Parkinson's disease,[30]