Melatonin: quantitative analysis in pharmaceutical oral dosage forms using thin-layer chromatography (TLC) densitometry

Up-to-date studies regarding the determination of melatonin by chromatographic methods

Melatonin is an indolic compound that has been reported in the literature to exist in human-based samples, vertebrates, vegetables, fruits, and pharmaceutical products. Melatonin is considered a dietary supplement and can regulate circadian rhythms, although it has not been classified as a drug by the US Food and Drug Administration. Several analytical methods have been used for its detection. This study aimed to summarize the recent outcomes of the chromatographic methods such as electrophoretic methods, gas chromatography, and liquid chromatography, which have been used for the determination of melatonin in the last three decades, with the focus on gas chromatography and high-performance liquid chromatography methods.

Microbial production of beneficial indoleamines (serotonin and melatonin) with potential application to biotechnological products for human health

Micro-organisms have showed the ability to produce biologically active compounds associated with neurotransmission in higher organisms. In particular, serotonin- and melatonin-producing microbes are valuable sources for the development of eco-friendly bioproducts. Serotonin and melatonin are indoleamines that have received special attention due to their positive effects on human health. These biomolecules exert a critical role in several physiological or pathological processes, including some mental and neurological disorders. This article includes a review of the microbial production of serotonin and melatonin, their functions in micro-organisms and their potential uses as therapeutic and/or preventive agents to improve human health. A description of the quantification methods employed to detect indoleamines and the evidence found concerning their microbial production at laboratory and industrial scale-for application in biotechnological products-is also provided. The microbial ability to synthesize beneficial indoleamines should be further studied and harnessed, to allow the development of sustainable bioprocesses to produce foods and pharmaceuticals for human health.

Melatonin: comprehensive profile

This chapter includes the aspects of melatonin. The drug is synthesized in the pineal gland starting from tryptophane or synthetically by using indole as starting material. Melatonin has been used as an adjunct to interleukin-2 therapy for malignant neoplasms, as contraceptive, in the management of various forms of insomnia, to alleviate jet lag following long flights, and finally as free radical scavenger and hence as an antioxidant and an anti-inflammatory. The chapter discusses the drug metabolism and pharmacokinetics and presents various method of analysis of this drug such as biological analysis, spectroscopic analysis, and chromatographic techniques of separation. It also discusses its physical properties such as solubility characteristics, X-ray powder diffraction pattern, and thermal methods of analysis. The chapter is concluded with a discussion on its biological properties such as activity, toxicity, and safety.

Melatonin as an antioxidant and its semi-lunar rhythm in green macroalga Ulva sp

The presence and role of melatonin in plants are still under debate owing to difficulties of identification and quantification. Accordingly, although it has been frequently proposed that melatonin acts as an antioxidant in phototrophic organisms, experimental data on its physiological role are scarce. This study describes the use of a rapid and simple new method for quantification of melatonin in the marine macroalga Ulva sp., organisms routinely exposed to tide-related environmental stresses and known for their high tolerance to abiotic conditions. The method was used here to show that exposure to oxidative stress-inducing environmental conditions (elevated temperature and heavy metals) induced a rise in melatonin level in the algae. Addition of exogenous melatonin alleviated the algae from cadmium-induced stress. Interestingly, although the algae were taken from a culture growing free floating and kept under constant photoperiod and water level, they exhibited a semi-lunar rhythm of melatonin levels that correlated with predicted spring tides. The correlation can probably be interpreted as reflecting preparation for predicted low tides, when the algae are exposed to increasing temperature, desiccation, and salinity, all known to induce oxidative stress. Given the simplicity of the described method it can easily be adapted for the study of melatonin in many other phototrophic organisms. These results provide, for the first time, experimental data that support both an antioxidant role for melatonin and its semi-lunar rhythm in macroalgae.

The quality of commercially available nutraceutical supplements and food sources

OBJECTIVES

Nutraceuticals are components of dietary origin, with claimed beneficial therapeutic activities. The quality of nutraceuticals is paramount for efficacy and safety, and it includes quality of raw materials, different available chemical forms, complex products, lack of substitution of inappropriate materials, and the absence of contaminants. The aim of this review is to investigate the extent of substandard formulated and raw material nutraceuticals, and to highlight any consequent health concern.

KEY FINDINGS

Reports of the quality of raw materials have revealed wide variations, often as a result of lack of clear regulatory definitions with respect to size of polymeric entities and also presence of glycosidic and salt forms. Published evaluations of over 70 formulations of 25 different nutraceuticals revealed variable quality; no nutraceutical showed consistent high quality, but a number revealed consistent low quality, thereby making the case for closer regulation of manufacturers. Whole food sources have also been shown to be widely variable in constituent levels. The effect of different formulations requires consideration, as the different types have been shown to have marked effects on bioavailability.

SUMMARY

The poor quality of commercially available nutraceuticals has been highlighted. In addition, incidences of side effects and drug interactions are increasing, as consumption of nutraceuticals rises. Pharmacists and health practitioners need to be aware of the scientific literature to advise accordingly.

Quantitative analysis of barakol content in Senna siamea leaves and flowers by TLC-densitometry

OBJECTIVE

To develop a TLC-densitometric method for the determination of barakol content in Senna siamea leaf and flower extracts, and to compare the barakol content in mature leaves, young leaves and young flowers of the plant which are consumed as a vegetable in curry.

MATERIALS AND METHODS

The extraction of pure barakol was performed by boiling the fresh young leaves of S. siamea with 0.5% sulfuric acid followed by chloroform extraction. The extract was further purified and recrystallized from absolute ethanol. Authentic sample of barakol was used for the validation of the TLC-densitometric method. Chromatography was performed on a TLC aluminium plate precoated with silica gel 60 F(254)as a stationary phase and chloroform-methanol (85:15 v/v) as a solvent system. Fifteen percent ethanolic extracts of mature leaves, young leaves and flowers of S. siamea were analyzed and compared for barakol content using the validated TLC-densitometric method. Both the validation and analysis of barakol by TLC-densitometry were carried out at the absorbance mode of 366 nm.

RESULTS

Barakol was extracted as pure lemon-yellow crystals from young S. siamea leaves with 0.1% yield. Linearity was found over the range of 200-900 ng/spot (r(2) = 0.997). The developed method gave high precision (%RSD < 0.50) and accuracy (average 101.12%). The limit of detection and limit of quantitation were 8 and 50 ng, respectively. Barakol content in young leaves, mature leaves and young flowers were 1.67, 0.78 and 1.43% dry weight, respectively. R(f) value of the barakol in young leaves, young flowers and authentic sample was the same: 0.45 +/- 0.03.

CONCLUSION

The TLC-densitometric method was simple, precise and convenient; hence it is an effective procedure for the simultaneous determination of barakol in plant extracts.

Photostability of drugs: photodegradation of melatonin and its determination in commercial formulations

The photostability of melatonin, a hormone used as supplementary drug in the alleviation of jet-lag and other sleep disorders, was studied. The drug photodegradation at different pH values was monitored by HPLC methods. The main photoproduct was isolated and characterised on the basis of the NMR, FTIR, and mass spectra. A HPLC method, in combination with a post-column on-line photochemical derivatisation was developed for the selective and reliable quality control of commercially available melatonin containing products.