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Melatonin (N-acetyl-5-methoxytryptamine) is an indole molecule widely found in animals and plants. It is well known that melatonin improves plant resistance to various biotic and abiotic stresses due to its potent free radical scavenging ability while being able to modulate plant signaling and response pathways through mostly unknown mechanisms. In recent years, an increasing number of studies have shown that melatonin plays a crucial role in improving crop quality and yield by participating in the regulation of various aspects of plant growth and development. Here, we review the effects of melatonin on plant vegetative growth and reproductive development, and systematically summarize its molecular regulatory network. Moreover, the effective concentrations of exogenously applied melatonin in different crops or at different growth stages of the same crop are analysed. In addition, we compare endogenous phytomelatonin concentrations in various crops and different organs, and evaluate a potential function of phytomelatonin in plant circadian rhythms. The prospects of different approaches in regulating crop yield and quality through exogenous application of appropriate concentrations of melatonin, endogenous modification of phytomelatonin metabolism-related genes, and the use of nanomaterials and other technologies to improve melatonin utilization efficiency are also discussed.

This review gives a comparative evaluation of the radioprotective properties and the therapeutic index (TI) of radioprotectors from various pharmacological group in experiments on both small and large animals. It presents a hypothesis explaining the decrease in the TI of cystamine and 5-methoxytryptamine (mexamine), and the retention of that of α1-adrenomimetic indralin, and also compares the effects on large and small animals. The considerable differences in the therapeutic indices of catecholamines, serotonin and cystamine are a consequence of specific features of their mechanisms of radioprotective action. Radioprotectors acting via receptor mediation tend to provide a more expanded window of protection. The reduction in the TI of cystamine in larger animals, such as dogs, may be caused by the greater increase in toxicity of aminothiols in relation to the decrease in their optimal doses for radioprotective effect in going from mice to dogs, which is a consequence of the slower metabolic processes in larger animals. The somatogenic phase of intoxication by cystamine is significantly longer than the duration of its radioprotective effect, and increases with irradiation. The decrease in the radioprotective effect and the TI of mexamine in experiments with dogs may be caused by their lower sensitivity to the acute hypoxia induced by the mexamine. This is because of lower gradient in oxygen tension between tissue cells and blood capillaries under acute hypoxia that is determined by lower initial oxygen consumption in a large animal as compared with a small animal. Indralin likely provides optimal radioprotective effects and a higher TI for large animals via the increased specificity of its adrenergic effect on tissue respiration, which supports the development of acute hypoxia in the radiosensitive tissues of large animals. The stimulatory effect of indralin on early post-irradiation haematopoietic recovery cannot provide a high level of radioprotective action for large animals, but it may promote recovery.

Recent additions of designer tryptamines and phenethylamines to the Drug Enforcement Administration's schedule of controlled substances necessitate analytical procedures for their detection and quantitation. As specific immunoassays are not currently available and cross-reactivities with existing assays are unknown, a screening method based on gas chromatography-mass spectrometry was developed. The method was capable of measuring the pentafluoropropionic derivatives of a-methyltryptamine (AMT), N,N-dimethyltryptamine (DMT), 4-bromo-2,5-dimethoxy-beta-phenethylamine (2CB), N,N-dipropyltryptamine (DPT), 2,5-dimethyl-4-N-propylthio-beta-phenethylamine (2C-T-7), and 5-methoxy-N,N-diisopropyltryptamine (5-MeO-DiPT). Separation was optimized to allow tentative identification of metabolites, which display common electron impact ionization fragmentation patterns. The screening method gave limits of detection between 5 and 10 ng/mL and demonstrated linearity between 50 and 1000 ng/mL. The method was successfully applied to blood and urine samples in suspected AMT intoxications. Confirmation of 5-MeO-DiPT in one of the subjects' urine was achieved using liquid chromatography-mass spectrometry (LC-MS). Quantitation by selected ion monitoring (SIM) yielded a urinary concentration of 229 ng/mL. The method was linear from 25 to 1500 ng/mL with a correlation coefficient of 0.995. The limit of detection was 5 ng/mL in urine on the LC-MS. Two additional peaks were observed and presumed to be metabolic products reported previously as 5-methoxy-N-isopropyltryptamine (5-MeO-iPT) and 5-methoxy-N,N-diisopropyltryptamine-N'-oxide (5-MeO-DiPT-N-oxide).

Foxy is slang for 5-methoxy-N,N-diisopropyltryptamine. It has hallucinogenic properties, similar to other tryptamine compounds, and is mildly euphoric. This case report describes a 21-year-old Caucasian man who ingested a pill called Foxy containing an unknown amount of drug. He was observed in hospital for 2 h, during which time he had mild hallucinations and could not move his limbs. A urine sample was collected approximately 4 h after drug ingestion. The patient was then discharged with no follow up assessment. The 5-methoxy-N,N-diisopropyltryptamine was identified in the urine by gas chromatography-mass spectrometry. Standards prepared from the pure material were used in the identification. Quantitative analysis using the same analytical technique resulted in a urinary concentration of 1.7 micro g/mL. Through oxidative deamination, the metabolite, 5-methoxy-indole acetic acid, was formed. It was identified in the urine, and the concentration was determined to be 1.3 micro g/mL using gas chromatography-mass spectrometry. Two other compounds were discovered in the urine sample as a result of a routine drug screen. From their mass spectra, they were tentatively identified as 5-methoxy-N-isopropyltryptamine and 5-methoxy-N,N-diisopropyltryptamine-N'-oxide.

A series of tryptamine analogues has been prepared and tested for their 5-HT1 receptor agonist properties. The incorporation of an alkoxy group at the C-5 position of the indole nucleus resulted in a short-lived and dose-dependent immediate antihypertensive and bradycardic response in anaesthetized spontaneously hypertensive rats (SHR). In addition, a carbomethoxy function at the β-position of the side-chain of the tryptamines significantly increased the mean resting arterial blood pressure (MAP) in pithed rats and also produced contraction of the canine basilar artery in a dose-dependent fashion. Structure-activity relationships (SAR) suggest that the 5-alkoxy group is an important pharmacophore in the production of the antihypertensive effect and that the introduction of a hydroxymethylene group on the side-chain, instead of the carbomethoxy group, changed the receptor affinity profile.

The effect on sexual maturation of 6 different pineal indoles, including melatonin, and of the metabolite 6-hydroxymelatonin was studied in the male rat after daily injections from 20 to 40 days of age. Only 5-methoxytryptamine (5MT) and 6-hydroxymelatonin (6M), in addition to melatonin, inhibited the neuroendocrine-reproductive axis during sexual maturation. Their potencies when injected in the afternoon were in the range of one-twentieth to one-fifth that of melatonin. Like melatonin these two indoles had no effect when injected in the morning. N-acetylserotonin, serotonin, 5-hydroxytryptophol and 5-methoxytryptophol did not influence sexual maturation either when injected in the morning or in the afternoon. Chromatographic separation was performed on plasma extracts from rats injected daily with the biologically active indoles and killed 10-120 min after the last injection. This procedure confirmed that 6M injections did not increase plasma melatonin levels. In contrast, plasma melatonin levels in 5MT-treated rats were increased 1 h after the 5MT injection. These results suggest that 5MT or part of it might be acetylated to melatonin; thus inhibition of sexual maturation might be mainly due to melatonin. These results indirectly support the contention that melatonin is the principal pineal indoleamine playing a role during sexual maturation.

Isamide, the N-chloroacetyl derivative of 5-methoxytryptamine, produced a dose-dependent competitive blockade of uterine contractions in vitro induced by 5-HT. The pA2 value for the 5-HT-isamide interaction was 4.42. The blockade was short-lasting and reversible; after recovery, a dose-dependent increase in the uterine sensitivity to 5-HT was found. The blockade proved to be selective to the 5-HT receptor. The simultaneous application of 5-HT plus isamide partially prevented the 5-HT-induced auto blockade phenomenon. In addition, isamide did not affect the contractile responses of the uterus to oxytocin or bradykinin or the contractile effects of the rat vas deferens to adrenaline.