Quality Assessment of Melatonin Supplements Marketed in Brazil: Alarming Discrepancies

Melatonin (MLT) is a hormone naturally produced by the pineal gland at night. It has multifunctional properties, including the regulation of circadian rhythms, antioxidant effects, and potential treatments for insomnia and jet lag. Due to simplified regulatory processes, many supplements may present quality deviations. In Brazil, MLT was recently approved for sale in pharmacies at low dosages. In this study, we analyzed the quality of orodispersible tablets containing 0.21 mg of MLT. Characterization was performed using Fourier‐transform infrared spectroscopy (FTIR), differential scanning calorimetry (DSC), thermogravimetric analyses (TGA), and scanning electron microscopy (SEM) with an energy‐dispersive X‐ray spectrometer (EDS). A liquid chromatographic method with ultraviolet detection (LC/UV) was developed and validated, and used to perform the identification, assay, and content uniformity tests of the tablets. FTIR, DSC, and TGA analyses indicated excipient interference. SEM/EDS analysis revealed variations in formulation morphology and the presence of impurities, such as copper. The LC/UV method demonstrated precision, accuracy, and linearity, with a limit of detection (LOD) of 1.19 μg/mL and a limit of quantification (LOQ) of 3.98 μg/mL. Excipients and potential adulterants did not interfere with the specificity. Tablet weights ranged from 79 mg to 200 mg. The samples failed both the assay and content uniformity tests, with values ranging from 43% to 75% and from 30% to 78%, respectively. The low active ingredient content significantly compromises efficacy. These findings reinforce the need for standardization and increased regulatory oversight of dietary supplements to ensure efficacy and consumer safety.