Electrochemical Determination of Capsaicin and Silymarin Using a Glassy Carbon Electrode Modified by Gold Nanoparticle Decorated Multiwalled Carbon Nanotubes

Capsaicinoids in Food: An Update on Pretreatment and Analysis Methods since 2010

Capsaicinoids, whose basic chemical structure is the vanilla amide of n-nonanoic acid, are responsible for chili pepper fruits' spicy flavor (pungency) and multiple pharmacological actions. Capsaicinoids are widely used to produce intense flavor food additives due to their sensory attributes of pungency, aroma, and color. To ensure strict quality control for capsaicinoids and maximize their positive effects, valid and sensitive pretreatment and determination methods are urgently needed. Consequently, this review provides a comprehensive summary of capsaicinoids' preparation and analytical technologies in food samples. Pretreatment techniques mainly include liquid-liquid extraction, solid-phase extraction, solid-phase microextraction, and dispersive solid-phase microextraction, among others. Detection methods include liquid chromatography coupled with different detectors, gas chromatography, electrochemical sensor methods, capillary electrophoresis, etc. Furthermore, the advantages and disadvantages of various pretreatment and analytical methods are compared and discussed. Thus, the present paper has attempted to shed light on novel and traditionalpretreatment methods and determination approaches and provided proper comments about their new developments and applications.

Electronic Tongue Based on ZnO/ITO@glass for Electrochemical Monitoring of Spiciness Levels

Capsaicin, a chemical compound present in chili peppers, is widely acknowledged as the main contributor to the spicy and hot sensations encountered during consumption. Elevated levels of capsaicin can result in meals being excessively spicy, potentially leading to health issues, such as skin burning, irritation, increased heart rate and circulation, and discomfort in the gastrointestinal system and even inducing nausea or diarrhea. The level of spiciness that individuals can tolerate may vary, so what may be considered incredibly hot for one person could be mild for another. To ensure food safety, human healthcare, regulatory compliance, and quality control in spicy food products, capsaicin levels must be measured. For these purposes, a reliable and stable sensor is required to quantify the capsaicin level. To leverage the effect of zinc oxide (ZnO), herein, we demonstrated the one-step fabrication process of an electronic tongue (E-Tongue) based on an electrochemical biosensor for the determination of capsaicin. ZnO was electrodeposited on the indium tin oxide (ITO) surface. The biosensor demonstrated the two notable linear ranges from 0.01 to 50 μM and from 50 to 500 μM with a limit of detection (LOD) of 2.1 nM. The present study also included the analysis of real samples, such as green chilis, red chili powder, and dried red chilis, to evaluate their spiciness levels. Furthermore, the E-Tongue exhibited notable degrees of sensitivity, selectivity, and long-term stability for a duration of more than a month. The development of an E-Tongue for capsaicin real-time monitoring as a point-of-care (POC) device has the potential to impact various industries and improve safety, product quality, and healthcare outcomes.

Fluorimetric chemodosimeter for the detection of capsaicinoids in food matrices

Capsaicin is a major pungent capsaicinoids in chili pepper and it causes duodenal, liver, stomach and gastric cancer in human. Hence, the detection of capsaicinoids becomes important on health issues concern. Here we are reporting, the first organic molecule based fluorimetric sensor for capsaicin detection using simple fluorophore 4-3-(pyren-2-yl-acryloyl) phenyboronic acid (PAPA), which was synthesized via greener microwave method. The probe has detected the capsaicin selectively in presence of other biomolecules in human biofluids through the intramolecular charge transfer mechanism and supported with DFT studies. The sensor has shown an excellent response towards capsaicin from 2 to 40 µM and the limit of detection of 12.84 nM. Real time analysis was done in various food matrices having capsaicinoids and the results have clearly shown good agreement with our optimized data and it also evinced that the developed sensor can be applied to detect the level of pungency of capsaicinoids.

Highly Sensitive Capsaicin Electrochemical Sensor Based on Bimetallic Metal-Organic Framework Nanocage

The content of capsaicin can be used as exotic markers of kitchen recycled oil. In this study, a bimetallic MOF nanocage (Fe^III-HMOF-5) was successfully prepared by a one-step solvothermal method and used for electrode modification to prepare a highly sensitive electrochemical sensor for rapid detection of capsaicin. Capsaicin could be selectively immobilized onto the Fe^III-HMOF-5 surface during infiltrating adsorption, thus exhibiting very excellent sensing performance. The detection conditions of the sensor were optimized. Under optimum conditions, the electrochemical sensor can linearly detect capsaicin in the range between 1–60 μM with a detection limit of 0.4 μM. In addition, the proposed electrochemical sensor showed excellent stability and selectivity. The real sample tests indicated the proposed electrochemical sensor was comparable to conventional UV spectrophotometry.

Electroanalytical overview: the pungency of chile and chilli products determined via the sensing of capsaicinoids

When you bite into a chile pepper or eat food containing chile (chilli), one might feel heat, or other associated feelings, some good such as the release of endorphins, and some bad. The heat, or pungency, and related feelings from eating chile peppers are the result of their chemical composition, i.e. the concentrations of capsaicinoids. The major components are capsaicin and dihydrocapsaicin, which occur in chiles in the ratio of 6 : 4. Other capsaicinoids occur in smaller concentrations and are known as the "minor" capsaicinoids. Wilbur L. Scoville in 1912 created an organoleptic test, now known as the Scoville scale, which asked a panel of tasters to state when an increasingly dilute solution of the chile pepper in alcohol no longer burned the mouth. Following the Scoville scale, a plethora of analytical techniques later followed. In this overview, we explore the endeavours directed to the development of electrochemical-based sensors for the determination of capsaicin and related compounds, starting from their use in hyphenated laboratory set-ups to their modern use as stand-alone electroanalytical sensors. The latter have the advantage of providing a rapid and sensitive methodology that has the potential to be translated in the field; future trends and issues to be overcome are consequently suggested.

A simple and rapid electrochemical determination of pungency: Application to aqueous and ethanolic extracts of Capsicum annuum cubana red

Chili peppers are rich in ascorbic acid and capsaicin. In this article is proposed an easy, fast, sensitive, and inexpensive method for determining the pungency and content of ascorbic acid in chili pepper extracts. The voltammetric (cyclic and differential pulse) behavior of capsaicin on a glassy carbon electrode has been evaluated at different pH values. A calibration curve has been obtained for the peak current, IP, of capsaicin as a function of the capsaicin concentration, C, in differential pulse voltammetry in phosphate buffer solution at pH 7.0: IP(µA) = 0.0147 (±5.346·10−3) + 0.0507 (±8.984·10−4) C(µM), with limit of detection, LOD = 0.198µM, limit of quantification, LOQ = 0.660µM, and dynamic linear range from 0.660 to 20.9 µM. A variant of the standard addition method has been used for simultaneous determination of the pungency and ascorbic acid content of extracts of Capsicum annuum cubana red. In this case, the calibration for ascorbic acid was I(µA) = 0.467 (±0.012) + 2.039·10−3 (±4.601·10−5) VAA(L)), with LOD = 17.56 µL, LOQ = 58.55 µL, and dynamic linear range from 58.6 to 500 µL, being VAA the volume of 10-mM ascorbic acid added to 50 mL of solution. The ascorbic acid content was compared to that of a sweet pepper. The method is cheap, simple, and fast (30 min vs c.a. 2 h compared to the spectrophotometric method), its sensitivity being comparable to other more expensive and/or more laborious methods.

Oxidative Transformations of Lignans

Numerous oxidative transformations of lignan structures have been reported in the literature. In this paper we present an overview on the current findings in the field. The focus is put on transformations targeting a specific structure, a specific reaction, or an interconversion of the lignan skeleton. Oxidative transformations related to biosynthesis, antioxidant measurements, and total syntheses are mostly excluded. Non-metal mediated as well as metal mediated oxidations are reported, and mechanisms based on hydrogen abstractions, epoxidations, hydroxylations, and radical reactions are discussed for the transformation and interconversion of lignan structures. Enzymatic oxidations, photooxidation, and electrochemical oxidations are also briefly reported.

Nanomaterials: Electrochemical Properties and Application in Sensors

The unique properties of nanoparticles make them an extremely valuable modifying material, being used in electrochemical sensors. The features of nanoparticles affect the kinetics and thermodynamics of electrode processes of both nanoparticles and redox reactions occurring on their surface. The paper describes theoretical background and experimental studies of these processes. During the transition from macro- to micro- and nanostructures, the analytical characteristics of sensors modify. These features of metal nanoparticles are related to their size and energy effects, which affects the analytical characteristics of developed sensors. Modification of the macroelectrode with nanoparticles and other nanomaterials reduces the detection limit and improves the degree of sensitivity and selectivity of measurements. The use of nanoparticles as transducers, catalytic constituents, parts of electrochemical sensors for antioxidant detection, adsorbents, analyte transporters, and labels in electrochemical immunosensors and signal-generating elements is described.

Recent advances in the analysis of flavonolignans of Silybum marianum

Extracts of milk thistle (Silybum marianum, Asteraceae) have been recognized for centuries as remedies for liver and gallbladder disorders. The active constituents of milk thistle fruits are flavonolignans, collectively known as silymarin. Flavonolignans in S. marianum are structurally diverse, 23 constituents have been isolated from purple- and white-flowering variants. Flavonolignans have a broad spectrum of bioactivities and silymarin has been the subject of intensive research for its profound pharmacological activities. Silymarin is extracted from the seeds, commercialized in standardized form, and widely used in drugs and dietary supplements. The thorough analysis of silymarin, its constituents and silymarin-containing products has a key role in the quality control of milk thistle-based products. Due to the low concentration of analytes, especially pharmacological and pharmacokinetic studies require more and more selective and sensitive, advanced techniques. The objective of the present review is to summarize the recent advances in the chemical analysis of S. marianum extracts, including the chemical composition, isolation and identification of flavonolignans, sample preparation, and methods used for qualitative and quantitative analysis. Various analytical approaches have been surveyed, and their respective advantages and limits are discussed.

Extraction and electrochemical detection of capsaicin and ascorbic acid from fresh chilli using ionic liquids

Capsaicin (flavour indicator) and ascorbic acid (vitamin C, freshness indicator) were simultaneously extracted from fresh chillies and quantified.