No full-text available
To read the full-text of this research,
you can request a copy directly from the authors.
Modernizing USP Melatonin Liquid Chromatographic Analyses for Increased Throughput and Reduced Environmental Impact
Abstract
Background
Melatonin supplements are often used to alleviate jetlag and other sleep-depletion related disorders. Recent studies found large inconsistencies between labeled values and actual contents of melatonin within products, which has led to concerns over the quality of melatonin supplements. In order to facilitate the quality control testing of melatonin supplements, an improved and more modern approach to the liquid chromatographic analysis of melatonin is required. In addition, growing public concern over the environmental footprint of analytical laboratories exacerbates the need to modernize legacy analytical procedures with more eco-friendly or greener approaches.
Objective
This study aims to optimize the routine liquid chromatographic analyses that are prescribed in the US Pharmacopeia (USP) melatonin monograph on a High Performance Liquid Chromatography (HPLC) system without fundamentally modifying the methods.
Method
The melatonin assay and the melatonin related compounds (impurities) test were optimized on a C18 column packed with 2.5 µm particles. The column length and the gradient elution parameters were adjusted following the guidelines on Adjustment of Chromatographic Conditions in USP General Chapter <621>. The mobile phase compositions were optimized to meet the system suitability requirements that were specified in the USP melatonin monograph. The flow rate was optimized for better separation efficiency.
Results
The optimized HPLC methods not only met the USP system suitability requirements in relative retention time (RRT), resolution, and relative standard deviation (RSD), but also demonstrated excellent linearity, sensitivity, accuracy, precision (repeatability), and would have a lower environmental impact.
Conclusions
The optimized HPLC methods for assay of melatonin and test of its related compounds achieved significantly increased throughput and a reduced environmental impact, without fundamentally modifying the methods.
Highlights
The optimized HPLC methods are significantly faster and more eco-friendly. These methods can be implemented on HPLC systems without a full re-validation.
ResearchGate has not been able to resolve any citations for this publication.
Melatonin is an endogenous neurohormone that regulates the sleep-wake cycle (1). It is used therapeutically for insomnia in adults and for primary sleep disorders in children (2). Melatonin is regulated by the Food and Drug Administration (FDA) as a dietary supplement. Various synthetic melatonin preparations are widely available over the counter (OTC) in the United States with sales increasing from 821 million in 2020 (3). Children are at increased risk for melatonin exposure because of the supplement's widespread use and growing popularity as a sleep aid. In 2020, melatonin became the most frequently ingested substance among children reported to national poison control centers (4); however, more research is needed to describe the toxicity and outcomes associated with melatonin ingestions in children. This study assessed isolated melatonin ingestions among the pediatric population (defined here as children, adolescents, and young adults aged ≤19 years) during January 1, 2012-December 31, 2021, using the American Association of Poison Control Centers' National Poison Data System (NPDS). During the 10-year study period, 260,435 pediatric melatonin ingestions were reported to NPDS, and the annual number of ingestions increased 530%. In addition, pediatric melatonin ingestions accounted for 4.9% of all pediatric ingestions reported to poison control centers in 2021 compared with 0.6% in 2012. Pediatric hospitalizations and more serious outcomes due to melatonin ingestions increased during the study period, primarily related to an increase in unintentional ingestions among children aged ≤5 years. Five children required mechanical ventilation, and two died. Consumers and health care professionals should be encouraged to report any melatonin product-related adverse events to MedWatch, the FDA's medical product safety reporting program. Public health initiatives should focus on raising awareness of increasing numbers of melatonin ingestions among children and on the development of preventive measures to eliminate this risk.
Melatonin is a hormone secreted in the pineal gland with several functions, especially regulation of circadian sleep cycle and the biological processes related to it. This review evaluates the bioavailability of melatonin and resulting metabolites, the presence of melatonin in wine and beer and factors that influence it, and finally the different benefits related to treatment with melatonin. When administered orally, melatonin is mainly absorbed in the rectum and the ileum; it has a half-life of about 0.45–1 h and is extensively inactivated in the liver by phase 2 enzymes. Melatonin (MEL) concentration varies from picograms to ng/mL in fermented beverages such as wine and beer, depending on the fermentation process. These low quantities, within a dietary intake, are enough to reach significant plasma concentrations of melatonin, and are thus able to exert beneficial effects. Melatonin has demonstrated antioxidant, anticarcinogenic, immunomodulatory and neuroprotective actions. These benefits are related to its free radical scavenging properties as well and the direct interaction with melatonin receptors, which are involved in complex intracellular signaling pathways, including inhibition of angiogenesis and cell proliferation, among others. In the present review, the current evidence on the effects of melatonin on different pathophysiological conditions is also discussed.
Sleep disorders are a group of conditions that affect the ability to sleep well on a regular basis and cause significant impairments in social and occupational functions. Although currently approved medications are efficacious, they are far from satisfactory. Benzodiazepines, antidepressants, antihistamines and anxiolytics have the potential for dependence and addiction. Moreover, some of these medications can gradually impair cognition. Melatonin (N-acetyl-5-methoxytryptamine) is an endogenous hormone produced by the pineal gland and released exclusively at night. Exogenous melatonin supplementation is well tolerated and has no obvious short- or long-term adverse effects. Melatonin has been shown to synchronize the circadian rhythms, and improve the onset, duration and quality of sleep. It is centrally involved in anti-oxidation, circadian rhythmicity maintenance, sleep regulation and neuronal survival. This narrative review aims to provide a comprehensive overview of various therapeutic functions of melatonin in insomnia, sleep-related breathing disorders, hypersomnolence, circadian rhythm sleep-wake disorders and parasomnias. Melatonin offers an alternative treatment to the currently available pharmaceutical therapies for sleep disorders with significantly less side effects.
There is currently no doubt about the serious threat that oxidative stress (OS) poses to human health. Therefore, a crucial strategy to maintain a good health status is to identify molecules capable of offering protection against OS through chemical routes. Based on the known efficiency of the phenolic and melatonin (MLT) families of compounds as antioxidants, it is logical to assume that phenolic MLT-related compounds should be (at least) equally efficient. Unfortunately, they have been less investigated than phenols, MLT and its non-phenolic metabolites in this context. The evidence reviewed here strongly suggests that MLT phenolic derivatives can act as both primary and secondary antioxidants, exerting their protection through diverse chemical routes. They all seem to be better free radical scavengers than MLT and Trolox, while some of them also surpass ascorbic acid and resveratrol. However, there are still many aspects that deserve further investigations for this kind of compounds.
This study assesses the actual measured quantities of melatonin and cannabidiol (CBD) in products marketed and sold in the US as melatonin gummies compared with the quantities declared on their labels.
Analytical metrics allow a periodic, healthy examination of methods and how they impact the environment, while ensuring that procedures are reproducible, reliable, repeatable, transferable and of high quality. This article provides a review of current trends with analytical metrics, such as the analytical method green score (AMGS). More importantly, the AMGS impact on sample preparation, development strategy and energy consumption considerations are provided. Finally, recent uses of metrics with specific relevance to the pharmaceutical research and development area through method transfer are covered.
In recent years, people have become increasingly interested in bioactive ingredients from plants, especially antioxidant molecules such as melatonin, which are beneficial to human health. The purpose of this article is to provide new information on plant-derived foods with a high content of melatonin. We comprehensively summarize the content of melatonin in plant-derived foods and discuss the factors that influence melatonin levels to provide new ideas on enhancement. Additionally, we describe the biosynthetic pathway of melatonin and identify its major functions. Medicinal herbs are often rich in melatonin while many vegetables and fruits exhibit somewhat lower levels with wide variations among species. The genetic traits of plants, the phenological stage of the cultivar, the photoperiod, the level of stress to which the plants are exposed at the time of harvest, exposure to agrochemicals and determination methods are the main factors affecting the melatonin content. To date, standardization of uniform sampling times and the use of suitable pretreatments as well as determination methods have not been achieved. The results of the studies reviewed highlight the potentially important role of plant melatonin in influencing the progression of human diseases. Based on the health promotional aspects of melatonin, consuming foods containing higher concentrations of tryptophan and melatonin is suggested.
Green and sustainable processes to develop and manufacture pharmaceuticals using eco-friendly and environmentally responsible means have been underway for over 25 years. These include the major analytical chemistry techniques used for pharmaceutical characterization. The pharmaceutical industry as a whole needs to responsibly transition away from traditional chromatographic methodologies that include the use of longer columns, extended run times, toxic non-polar solvents (e.g. heptanes and hexanes for normal phase liquid chromatography) and their accompanying large solvent volume consumption - toward more efficient, greener solutions. Over the last decade, high pressure liquid chromatography (HPLC) and supercritical fluid chromatography (SFC) techniques have undergone substantial improvements to instrumentation (e.g. UHPLC and UHPSFC) and column particle technologies, all of which lead to faster and more efficient separations while reducing development and validation time for both chiral and achiral analyses. However, many of these advances have yet to be globally adopted in later stage drug development and manufacturing where chromatographic process usage requires multiple analyses for every method transfer, validation, and clinical supply campaign. In order to emphasize greener method alternatives, we introduce a new approach to definitively establish the impact of method design and instrument selection choices. Our aim is to provide awareness and guidance to the global industry with a single unified, straightforward metric that clearly shows the benefit of selecting more modernized, safer and more environmentally-friendly methods and techniques without compromising separation performance.
Objective:
We describe the purpose of the Dietary Supplement Ingredient Database (DSID), the statistical methodology underlying online calculators of analytically verified supplement content estimates, and the application and significance of DSID label adjustments in nutritional epidemiology.
Background and history:
During dietary supplement (DS) manufacturing, many ingredients are added at higher than declared label amounts, but overages are not standardized among manufacturers. As a result, researchers may underestimate nutrient intakes from DSs. The DSID provides statistical tools on the basis of the results of chemical analysis to convert label claims into analytically predicted ingredient amounts. These adjustments to labels are linked to DS products reported in NHANES.
Rationale:
Tables summarizing the numbers of NHANES DS products with ingredient overages and below label content show the importance of DSID adjustments to labels for accurate intake calculations.
Recent developments:
We show the differences between analytically based estimates and labeled content for vitamin D, calcium, iodine, caffeine, and omega-3 (n-3) fatty acids and their potential impact on the accuracy of intake assessments in large surveys. Analytical overages >20% of label levels are predicted for several nutrients in 50-99% of multivitamin-mineral products (MVMs) reported in NHANES: for iodine and selenium in adult MVMs, for iodine and vitamins D and E in children's MVMs, and for iodine, chromium, and potassium in nonprescription prenatal MVMs. Predicted overages of 10-20% for calcium can be applied to most MVMs and overages >10% for folic acid in the vast majority of adult and children's MVMs.
Future directions:
DSID studies are currently evaluating ingredient levels in prescription prenatal MVMs and levels of constituents in botanical DSs.
Conclusions:
We estimate that the majority of MVM products reported in NHANES have significant overages for several ingredients. It is important to account for nonlabeled additional nutrient exposure from DSs to better evaluate nutritional status in the United States.
Study objectives:
Melatonin is an important neurohormone, which mediates circadian rhythms and the sleep cycle. As such, it is a popular and readily available supplement for the treatment and prevention of sleep-related disorders including insomnia and jet lag. This study quantified melatonin in 30 commercial supplements, comprising different brands and forms and screened supplements for the presence of serotonin.
Methods:
A total of 31 supplements were analyzed by ultraperformance liquid chromatography with electrochemical detection for quantification of melatonin and serotonin. Presence of serotonin was confirmed through analysis by ultraperformance liquid chromatography with mass spectrometry detection.
Results:
Melatonin content was found to range from -83% to +478% of the labelled content. Additionally, lot-to-lot variable within a particular product varied by as much as 465%. This variability did not appear to be correlated with manufacturer or product type. Furthermore, serotonin (5-hydroxytryptamine), a related indoleamine and controlled substance used in the treatment of several neurological disorders, was identified in eight of the supplements at levels of 1 to 75 μg.
Conclusions:
Melatonin content did not meet label within a 10% margin of the label claim in more than 71% of supplements and an additional 26% were found to contain serotonin. It is important that clinicians and patients have confidence in the quality of supplements used in the treatment of sleep disorders. To address this, manufacturers require increased controls to ensure melatonin supplements meet both their label claim, and also are free from contaminants, such as serotonin.
We discuss the origins and the fundamentals of Green Analytical Chemistry (GAC), based on the literature published about clean, environmentally-friendly or GAC methods. We pay special attention to the strategies and the tools available to make sample-pretreatment and analytical methods greener. We consider that the main principles are to replace toxic reagents, to miniaturize and to automate methods, making it possible to reduce dramatically the amounts of reagents consumed and wastes generated, so reducing or avoiding side effects of analytical methods. We also consider on-line decontamination or passivation of wastes to be of special interest in making analytical chemistry sustainable.
Melatonin functions as a free radical scavenger and controls the regulation of the sleep–wake cycle in mammals, while serotonin
is the main intermediate in melatonin biosynthesis. In this paper, melatonin and serotonin have been detected and quantified
for the first time in eight different sweet cherry cultivars using high performance liquid chromatography with mass spectrometry
detection. The limits of detection of the proposed analytical method were 4.3ng/mL for melatonin and 3.0ng/mL for serotonin.
An inverse relation between the contents of melatonin and serotonin was observed in the studied sweet cherry cultivars. The
highest melatonin amounts were found in ‘Burlat’ sweet cherries (22.4±1.3ng/100g of fresh fruit), while the highest serotonin
contents were found in the cultivar ‘Ambrunés’ (37.6±1.4ng/100g of fresh fruit). The results presented in this research
allow us to know the amount of melatonin and serotonin bring to the diet.
Melatonin exists in a considerable variety of plant species. However, the physiological roles of melatonin in plants are not well understood. In this study, the distribution and accumulation of melatonin during leaf and fruit development were analyzed in Micro-Tom, a model cultivar of tomato (Solanum lycopersicum L.). Melatonin was extracted using an acetone-methanol method and measured by enzyme-linked immunosorbent assay. Melatonin was detected in leaves, stems, roots, flowers, fruits, seedlings and seeds in the range of 1.5-66.6 ng/g fresh weight, with seeds containing the highest concentration of melatonin. In fruits and leaves, melatonin concentrations varied depending on the developmental stage, suggesting that melatonin controls some of the processes involved in plant maturation.
Immunoassays were investigated for the determination of melatonin in biological samples in the presence of a naphthalenic structural analogue S 20098, which is currently under development as a melatonin agonist. The lack of specificity of commercially available antibodies in the presence of closely related molecules led us to develop an LC-RIA procedure with a quantification limit set at 15 pg/ml(-1). Because this technique was not sensitive enough and difficult to use on a routine basis, a more sensitive GC-MS technique was developed. This method involved automated solid-phase extraction (plasma) or liquid-liquid extraction (saliva), derivatization of the indolic moiety and GC separation with an automated switching device before MS detection. The method was validated over the range 1-100 pg/ml(-1), with a quantification limit set at 1 pg/ml(-1) in human plasma and saliva. Intra-assay and inter-assay precision and accuracy were within 16% for all concentrations investigated and each biological matrix. The stability of melatonin in plasma and saliva under various storage conditions was also determined. The specificity of the assay for the analysis of melatonin in the presence of S 20098 and its metabolises was demonstrated. The method was subsequently applied for the determination of endogenous melatonin concentrations in plasma and saliva samples from clinical studies performed with S 20098 to provide pharmacodynamic data.
The seeds of plants represent the anlage of the next generation and are vital to their existence. Melatonin has been identified in the leaves and flowers of plants but not in seeds. In this study, we examined the seeds of 15 edible plants for the presence of melatonin which was extracted using cold ethanol. Melatonin was initially identified by radioimmunoassay and subsequently quantified and confirmed using high performance liquid chromatography. The physiological concentrations of melatonin in the 15 seeds studied ranged from 2 to 200 ng/g dry weight. The highest concentrations of melatonin were observed in white and black mustard seeds. This level of melatonin is much higher than the known physiological concentrations in the blood of many vertebrates. Since the seed, particularly its germ tissue, is highly vulnerable to oxidative stress and damage, we surmise that melatonin, a free radical scavenger, might be present as an important component of its antioxidant defense system. Thus, melatonin in seeds may be essential in protecting germ and reproductive tissues of plants from oxidative damage due to ultraviolet light, drought, extremes in temperature, and environmental chemical pollutants.
Melatonin is a highly conserved molecule that not only exists in animals, but also is present in bacteria, unicellular organisms and in plants. Since melatonin is an antioxidant, in plants melatonin was speculated to protect them from intrinsic and environmental oxidative stress. More importantly, melatonin in edible plants inevitably enters animals and human through feed and food. In this study, more than 100 Chinese medicinal herbs were analyzed using the methods of solid phase extraction and HPLC-FD on-line with MS to determine whether melatonin is present in these commonly used herbs. Melatonin was detected in majority of these plants. Sixty-four of them contain melatonin in excess of 10 ng per gram dry mass. Melatonin levels in several herbs are in excess of 1000 ng/g. It is well known that normal average physiological plasma levels of melatonin are only 10-60 pg/mL. These high level-melatonin containing plants are traditionally used to treat diseases which presumably involve free radical damage. The current study provides new information concerning one potentially effective constituent present in a large number of medicinal herbs. The results suggest that these herbs should be reevaluated in reference to their nutritional and medicinal value.
We investigated whether melatonin is present in walnuts (Juglans regia L.) and, if so, tested whether eating walnuts influences melatonin levels and the total antioxidant status of the blood.
Melatonin was extracted from walnuts and quantified by high-performance liquid chromatography. After feeding walnuts to rats, serum melatonin concentrations were measured using a radioimmunoassay and the "total antioxidant power" of the serum was estimated by using the trolox equivalent antioxidant capacity and ferric-reducing ability of serum methods.
Mean +/- standard error melatonin concentrations were 3.5 +/- 1.0 ng/g of walnut. After food restriction of rats and then feeding them regular chow or walnuts, blood melatonin concentrations in the animals that ate walnuts were increased over those in the rats fed the control diet. Increases in blood melatonin were also accompanied by increases in trolox equivalent antioxidant capacity and ferric-reducing ability of serum values.
Melatonin is present in walnuts and, when eaten, increase blood melatonin concentrations. The increase in blood melatonin levels correlates with an increased antioxidative capacity of this fluid as reflected by augmentation of trolox equivalent antioxidant capacity and ferric-reducing ability of serum values.
- United States Pharmacopeia