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Objective: To identify the phytochemical constituents of Peganum harmala L. (P. harmala) seeds extract by gas chromatography-mass spectrometer (GC-MS) and evaluate their antidepressant activity. Methods: The seeds extract was analyzed by GC-MS to identify their major chemical compounds. The antidepressant activity of P. harmala was demonstrated using the forced swim test and the adrenocorticotropic hormone analysis. After oral administration of the seeds extract and diazepam in rats, the immobility time in the forced swim test was measured and the defecation rate was estimated for all rats. Results: GC-MS analysis showed the presence of indole alkaloids (β-carboline), for exmaple harmaline (48.009%), harmine (38.440%), tetrahydroharmine (8.513%), tetrahydroharman (0.061%) and 6-methoxytetrahydro-1-norharmanone (0.057%) were present in the extract. The results showed that the P. harmala extract (100 mg/kg and 300 mg/kg) were able to reduce the immobility time (80.20 ± 9.01, 46.80 ± 8.53; P < 0.001), the adrenocorticotropic hormone rate (131.33 ± 12.72, 49.72 ± 13.03; P < 0.001) and the defecation rate (1.400 ± 1.342, 0.600 ± 0.548; P < 0.01), respectively. Conclusions: This indicates that the seeds extract can correct the depression and reach the normal state of the treated animals. The results demonstrated that seeds represented a source of indole alkaloids (harmaline, harmine and tetrahydroharmine).

There is a general consensus in dentistry that successful local anesthesia is frequently difficult in habitual drinkers and alcoholic patients. Neuro-active tetrahydroharmans increase in human body fluids and tissues by consuming alcoholic beverages. To understand such reduced anesthetic efficacy by the drug interaction hypothesis, we studied the influences of drinking-related tetrahydroharmans on membrane fluidization as one of local anesthetic mechanisms. Liposomal membranes prepared with phosphatidylcholine and cholesterol were treated with lidocaine and different tetrahydroharmans separately and in combination, followed by measuring fluorescence polarization to determine their induced changes in membrane fluidity. In contrast to 0.1–2 mg/mL lidocaine, tetrahydroharmans decreased the fluidity of membrane preparations at ∼25 μg/mL with the potency being 1,2,3,4-tetrahydroharman ≫ 1,2,3,4-tetrahydronorharman. 1,2,3,4-Tetrahydroharman counteracted the membrane-fluidizing effects of 1 mg/mL lidocaine at physiologically relevant 0.25–2.5 ng/mL, whereas neither its 6-hydroxyl nor 7-hydroxyl metabolite did at 25–200 ng/mL. Such counteraction at a membrane lipid level may be responsible for the reduction of local anesthetic efficacy in drinkers because 1,2,3,4-tetrahydroharman increases in vivo by ingesting alcoholic beverages.

Summary 4-Dimethylaminoazobenzene is only a weak mutagen on Salmonella typhimurium strains TA100 and TA98, although it is a fairly strong carcinogen. Norharman, which is present in tobacco smoke and tryptophan pyrolysate, enhanced the mutagenicity of 4-dimethylaminoazobenzene on strain TA98 about 40-fold. Norharman alone had no mutagenic activity on TA98 and so it is a ‘Comutagen’. The mutagenicities of 4-methylaminoazobenzene, 3′-methyl-4-dimethylaminoazobenzene, 4-aminoazobenzene and 4′-methoxycarbonyl-N-hydroxy-4-methylaminoazobenzene were all potentiated by norharman. Presence of a metabolic activation system was essential for comutagenic action of norharman with these compounds. Dihydronorharman, tetrahydronorharman, 9-methyl-β-carboline, harman and tetrahydroharman did not enhance the mutagenicity of 4-dimethylaminoazobenzene.

1-Methyl-1,2,3,4-tetrahydro-β-carboline-1-carboxylic acid (1-carboxytetrahydroharman, 1-CTHH) has been detected in the brain of rats following intracerebroventricular injection of tryptamine and pyruvic acid. We now report the metabolism of this compound. Following intraperitoneal injection of 1-CTHH into rats, harmalan was found to be the major metabolite besides tetrahydroharman (THH) and harman. A high concentration of THH was measured in the lung while most of harman was found in the urine. Harmalan and THH could be detected in the brain in low concentrations. The products were separated following extraction from tissues by high-performance liquid chromatography (HPLC) on a reversed phase C18-DB column. The identity of the metabolites was confirmed by mass spectrometry (MS) analysis. The results demonstrate the role of 1-CTHH as a precursor of the biologically active compounds harmalan, THH and harman.

In vivo metabolism of 1-methyl-1,2,3,4-tetrahydro-beta-carboline-1-carboxylic acid (1-CTHH), a possible precursor of the endogenous beta-carbolines tetrahydro-harman (THH) and harman was investigated in rats. Following intraperitoneal injection of [4-14C]1-CTHH, a rapid distribution of the radioactivity in the tissues was observed. The highest radioactivity was measured in the kidney and the lowest in the brain as well as in the fat tissue. Approximately 55% of the administered dose was excreted in the urine within 90 min. The radioactivity in the urine consisted of unchanged 1-CTHH (greater than 90%) besides harmalan and trace amounts of harman. Harmalan represents the major degradation product of 1-CTHH; it could be identified in all tissues examined and in the urine. The concentration in the blood, however, was low at all time points investigated. The peak concentration of harmalan in most tissues was measured between 15-30 min after injection. A time-dependent formation of THH was found in the lung and spleen indicating an important role of these organs in the biosynthesis of THH. Furthermore, the metabolism of [4-14C]1-CTHH in the brain was studied following intracerebroventricular injection. The formation of harmalan in the brain was not affected by pretreatment with the aromatic amino acid decarboxylase inhibitor NSD 1015. Determination of the harmalan concentration in several brain regions revealed a high level in the hippocampus and hypothalamus and a small concentration in pons, corpus striatum, cerebellum and cerebral cortex 20 min after injection. The analyses of the