Simple and Sensitive Voltammetric Determination of Esculetin Using Electrochemically Reduced Graphene Oxide Modified Electrode

Heparin-stabilized gold nanoparticles embedded in graphene for the electrochemical determination of esculetin

A conductive nanocomposite consisting of heparin-stabilized gold nanoparticles embedded in graphene was prepared and characterized to develop an electrochemical sensor for the determination of esculetin in tea and jam samples. The gold nanoparticles were characterized by spectroscopic and microscopic techniques. The different proportions of graphene in the nanocomposite were evaluated and characterized by electrochemical practices. The heterostructure material on the glassy carbon electrode with esculetin showed π-π stacking interactions with an adsorption-controlled process. The voltammetric profile of esculetin using the proposed nanomaterial presented oxidation and reduction peaks at +0.61 and +0.58 V vs. Ag/AgCl, respectively, facilitating the electron transfer with esculetin through the transfer of two moles of protons and two moles of electrons per mole of esculetin. Using optimized conditions and square wave voltammetry, the calibration curve was obtained with two linear ranges, from 0.1 to 20.5 μmol L-1, with a detection limit of 43.0 nmol L-1. The electrochemical sensor showed satisfactory results for repeatability and stability, although interferences were observed in the presence of high concentrations of ascorbic acid or quercetin. The sensor was successfully applied in the determination of esculetin in samples of mulberry jam, white mulberry leaf tea, and white mulberry powder tea, presenting adequate recovery ranges. This directive provides valuable insights for the development of novel electrochemical sensors using heparin-based conductive nanomaterials with improved sensitivity and sensibility.

Esculetin: A review of its pharmacology and pharmacokinetics

Esculetin is a natural dihydroxy coumarin; it is mainly extracted from twig skin and the trunk bark of the Chinese herbal medicine Fraxinus rhynchophylla Hance. Emerging evidence suggests that esculetin has a wide range of pharmacological activities. Based on its fundamental properties, including antioxidant, antiinflammatory, antiapoptotic, anticancer, antidiabetic, neuroprotective, and cardiovascular protective activities, as well as antibacterial activity, among others, esculetin is expected to be a therapeutic drug for specific disease indications, such as cancer, diabetes, atherosclerosis, Alzheimer's disease (AD), Parkinson's disease (PD), nonalcoholic fatty liver disease (NAFLD), and other diseases. The oral bioavailability of esculetin was shown by studies to be low. The extensive glucuronidation was described to be the main metabolic pathway of esculetin and C-7 phenolic hydroxyl to be its major metabolic site. With the development of scientific research technology, the pharmacological effects of esculetin are identified and its potential for the treatment of diseases is demonstrated. The underlining mechanisms of action and biological activities as well as the pharmacokinetic data of the analyzed compound reported so far are highlighted in this review with the aim of becoming a proven, and applicable insight and reference for further studies on the utilization of esculetin.