A rapid and simple procedure for the determination of synephrine in dietary supplements by gas chromatography-mass spectrometry

Scavenging Glyoxal and Methylglyoxal by Synephrine and Neohesperidin from Flowers of Citrus aurantium L. var. amara Engl. in Mice and Humans

There is considerable research evidence that α-dicarbonyl compounds, including glyoxal (GO) and methylglyoxal (MGO), are closely related to many chronic diseases. In this work, after comparison of the capture capacity, reaction pathway, and reaction rate of synephrine (SYN) and neohesperidin (NEO) on GO/MGO in vitro, experimental mice were administrated with SYN and NEO alone and in combination. Quantitative data from UHPLC-QQQ-MS/MS revealed that SYN/NEO/HES (hesperetin, the metabolite of NEO) could form the GO/MGO-adducts in mice (except SYN-MGO), and the levels of GO/MGO-adducts in mouse urine and fecal samples were dose-dependent. Moreover, SYN and NEO had a synergistic scavenging effect on GO in vivo by promoting each other to form more GO adducts, while SYN could promote NEO to form more MGO-adducts, although it could not form MGO-adducts. Additionally, human experiments showed that the GO/MGO-adducts of SYN/NEO/HES found in mice were also detected in human urine and fecal samples after drinking flowers of Citrus aurantium L. var. amara Engl. (FCAVA) tea using UHPLC-QTOF-MS/MS. These findings provide a novel strategy to reduce endogenous GO/MGO via the consumption of dietary FCAVA rich in SYN and NEO.

Scavenging Glyoxal and Methylglyoxal by Synephrine Alone or in Combination with Neohesperidin at High Temperatures

α-Dicarbonyl compounds, such as glyoxal (GO) and methylglyoxal (MGO), are a series of chemical hazards that exist in vivo and in vitro, posing a threat to human health. We aimed to explore the scavenging effects on GO/MGO by synephrine (SYN) alone or in combination with neohesperidin (NEO). First, through LC-MS/MS, we confirmed that both SYN and NEO could effectively remove GO and form GO adducts, while NEO could also clear MGO by forming MGO adducts, and its ability to clear MGO was stronger than that of GO. Second, a synergistic inhibitory effect on GO was found when SYN and NEO were used in combination by using the Chou-Talalay method; on the other hand, SYN could promote NEO to clear more MGO, although SYN could not capture MGO. Third, after synthesizing four GO/MGO-adducts (SYN-GO-1, SYN-GO-3, NEO-GO-7, and NEO-MGO-2) and identifying their structure through NMR, strict correlations between the GO/MGO-adducts and the GO/MGO-clearance rate were found when using SYN and NEO alone or in combination. Furthermore, it was inferred that the synergistic effect between SYN and NEO stems from their mutual promotion in capturing more GO by the quantitative analysis of the adducts in the combined model. Finally, a study was conducted on flowers of Citrus aurantium L. var. amara Engl. (FCAVA, an edible tea) rich in SYN and NEO, which could serve as an effective GO and MGO scavenger in the presence of both GO and MGO. Therefore, our study provided well-defined evidence that SYN and NEO, alone or in combination, could efficiently scavenge GO/MGO at high temperatures, whether in the pure form or located in FCAVA.

Synephrine, as a scavenger and promoter, cooperates with hesperidin to reduce acrolein levels

Acrolein (ACR) is a harmful and active aldehyde produced in processed food that endangers foods safety. We undertook this work to explore the ACR-trapping ability of hesperidin (HES) and synephrine (SYN) from the diet. After comparing their ACR-trapping abilities, the reaction pathways of HES and SNY were analyzed using LC-MS/MS, and two adducts (HES-ACR-1 and SNY-2ACR) were synthesized, and their structures were identified by NMR. Then, we not only evaluated the synergistic trapping effects of HES and SNY on ACR in the model through the Chou-Talalay method but verified it in the processing of roasted duck wings and cookies. Furthermore, based on the quantitative analysis of the ACR-adducts of HES and SNY, we demonstrated that SYN, as a promoter, could greatly improve the ACR-capturing ability of HES by forming more adducts (3-fold). Our findings could serve as a guide for using SNY and HES as new scavengers in food processing.

Disclosing Frauds in Herbal Food Supplements Labeling: A Simple LC-MS/MS Approach to Detect Alkaloids and Biogenic Amines

Food supplements are a category of products perceived safe and therefore commonly used by different categories of consumers without any particular attention or precaution. However, health risks associated with the consumption of supplements containing undeclared substances cannot be excluded. A variety of analytical methods are used to control supplement quality composition, but usually, these procedures are complex and time-consuming. Here, we report the results of a simple and fast liquid chromatography-tandem mass spectrometry (LC-MS/MS) method, to detect and quantify simultaneously different categories of active molecules, such as biogenic ammines and natural alkaloids that at high doses can produce negative health effect in consumers. Three categories of products intended for body weight loss, energy boosting, and erectile dysfunction treatment, purchased through e-commerce sites and from local supermarkets, were analyzed (n = 91). The caffeine, synephrine, agmatine sulfate, yohimbine, phenethylamine, and icariin were correctly separated and identified with good precision (RSD < 20%) and recovery (89-109%). The identification and quantification of the analytes in real samples highlighted that the 26% of the samples were not compliant with labeling, confirming that frauds are very common also in the natural supplements market. This LC-MS/MS method could be easily used to test natural supplements in order to check the correct labeling and to protect consumers from potential health risks and food frauds.

LC-HRMS analysis of 13 classes of pharmaceutical substances in food supplements

Food supplements should not contain substances considered unsafe or pose a health risk to consumers. In recent years illegal adulterants have been found in various functional foods without notification of their presence or amount in the labelling. In this study, a validated method was developed and applied as a screening method to detect 124 forbidden substances belonging to 13 classes of compounds in food supplements. Liquid chromatography coupled with high-resolution mass spectrometry (LC-HRMS) and a simple and rapid extraction protocol was applied to 110 food supplements collected from the internet market or during official controls in Italy. The percentage of non-compliant samples was 4.5%, relatively high compared with the official control results for these substances usually obtained on other food matrices. The results suggested the need to strengthen controls in this field to detect food supplement adulteration, which represents a potential health risk for the consumer.

Dietary supplement mislabelling: case study on selected slimming products by developing a green isocratic HPLC method for their quality control

Nowadays, a huge population consumes Dietary supplements for losing weight. Products are often claimed as botanical blends, yet they aren't necessarily safe. Misleading labels are also very common. Thus, validated analytical methods for a wide range of slimming compounds are highly needed. Herein, we present a simple HPLC/PDA method for the quantitation of seven popular slimming ingredients. Studied compounds were Caffeine, Raspberry Ketone, trans-Resveratrol, p-Synephrine, p-Octopamine, p-Hordenine and 2-phenethylamine. After optimization, separation was carried out on a C18 column and mobile phase was a mixture of Acetonitrile:Water containing 0.1% phosphoric acid (50:50, %v/v). The last compound was eluted at 9.76 min. Separation was efficient showing baseline- separated symmetric peaks, without using any gradient programs, organic mobile phase modifiers or modified stationary phases. Method validation was done following ICH guidelines. Calibration curves were linear over wide concentration ranges and calculated LOD values were in the range 0.02-0.09 µg/mL. Method greenness was assessed using Analytical Eco-scale, GAPI and AGREE metric tools. Further, four random sample products purchased from online supplement stores were assayed. Results proved some mislabeling actions. To support our findings, standard addition was carried out and average % recoveries were 96.67 - 101.44% with standard deviation ≤ 2.83 between measurements.

A new voltammetric platform for reliable determination of the sport performance-enhancing stimulant synephrine in dietary supplements using a boron-doped diamond electrode

For the first time, we propose a new modification-free voltammetric platform for simple, fast and reliable quantification of the sport performance-enhancing stimulant synephrine (SYN) based on the usage of a commercial screen-printed boron-doped diamond (BDD) electrochemical sensor. Applying cyclic voltammetry, SYN exhibited one well-shaped, irreversible and diffusion-driven oxidation peak at a peak potential of +1.45 V (vs. the silver pseudoreference electrode) in the presence of 2 M HClO₄. Under the selected experimental conditions, the following analytical parameters for determination of SYN were obtained: linear concentration ranges from 19.6 up to 1000 μM and from 9.9 up to 1000 μM for differential pulse (DPV) and square-wave voltammetry (SWV), respectively, detection limits at micromolar concentration levels and intra-day repeatability with a relative standard deviation below 4% for both pulse techniques. The interference study revealed fair selectivity when considering the target dietary supplements. The feasibility of the developed voltammetric platform was verified in the analysis of commercially available dietary supplements and reasonable recovery values were achieved by DPV and SWV, respectively. In addition, the method can be performed directly without higher consumption of chemicals, waste generation, complex sample extraction and higher instrumentation cost. The advanced BDD electrochemical sensor has appeared to be a suitable competitor for efficient applications in food quality control analysis.

Rapid Detection of Six Glucocorticoids Added Illegally to Dietary Supplements by Combining TLC with Spot-Concentrated Raman Scattering

The objective of this study was to establish a novel method for rapid detection of six glucocorticoids (prednisone, prednisone acetate, prednisolone, hydrocortisone, hydrocortisone acetate, and dexamethasone) added illegally in dietary supplements simultaneously by combining thin layer chromatography (TLC) with spot-concentrated Raman scattering (SCRS). The doping ingredients were separated by TLC, and viewed and located with UV light (254 nm), enriched by chromatography, then Raman spectra were directly detected by a Raman Imagine microscope with 780 nm laser source. This method had complementary advantages of TLC and Raman spectroscopy, which enhanced the specificity of the test results. The limit of detection (LOD) of the reference substances were 4 μg, 4 μg, 4 μg, 6 μg, 6 μg, and 4 μg, respectively. The method was used to study the six glucocorticoids added illegally in five dietary supplements. Fake drugs had been detected. The study showed that the TLC-SCRS method is simple, rapid, specific, sensitive, and reliable. The method could be used for effective separation and detection of six chemical components used in dietary supplement products, and would have good prospects for on-site qualitative screening of dietary supplement products for adulterants.

High-performance liquid chromatographic analysis of biogenic amines in pharmaceutical products containing Citrus aurantium

A reverse-phase (RP)-HPLC method is reported for determining L-tyrosine, p-octopamine, synephrine, tyramine and hordenine as chemical markers of the species Citrus aurantium in raw material, dry extracts and phytotherapeutic herbal formulations. Using RP-HPLC with diode array detection (DAD) and gradient elution, the amines were determined in 12 different products from different Brazilian states labelled as containing C. aurantium. The presence of the amines was confirmed by mass spectrometry using electrospray ionisation (ESI-MS/MS). This RP-HPLC method allowed the separation of the amines from complex mixtures containing caffeine, ephedrine, salicin and other raw materials (e.g. Garcinia camboja, Phaseolus vulgaris, Caralluma fimbriata, Cassia nomane, Ephedra sp. and Cordia ecalyculata). The method proved useful and selective for inspecting herbal medicines containing p-synephrine and structural analogues. The herbal products analysed had a p-synephrine content ranging from 0.005 to 4.0% (w/w).

Simultaneous determination of flavanones, hydroxycinnamic acids and alkaloids in citrus fruits by HPLC-DAD-ESI/MS

A simple and accurate method has been developed to simultaneously separate and determine 10 bioactive compounds in citrus fruits by high-performance liquid chromatography coupled with diode array detection and electrospray ionisation mass spectrometry (HPLC-DAD-ESI/MS). This HPLC assay was performed on a reversed-phase C18 column with acetonitrile and 0.1% (v/v) aqueous formic acid as mobile phase. DAD has been performed at 273, 283 and 324nm for quantification of the alkaloids, flavanones and hydroxycinnamic acids. MS was also employed to identify the each analyte. Ten analytes (naringin, hesperidin, neohesperidin, ferulic acid, p-coumaric acid, chlorogenic acid, caffeic acid, octopamine, synephrine and tyramine) demonstrated good linearity (r⩾0.9990) in a relatively wide concentration range. The method revealed high average recovery (range, 92.1-97.9%) and good precision with interday and intraday variations with less than 4.71%. The limits of detection (LODs) ranged from 0.02 to 0.11μg/ml, while the limits of quantification (LOQs) were defined in the range of 0.08-0.39μg/ml. The proposed method has been successfully applied to analyse three types of bioactive constituents in eight citrus hybrids pulps and eight citrus hybrids peels, which has been successfully cultivated in China.

Mass spectrometric determination of the predominant adrenergic protoalkaloids in bitter orange (Citrus aurantium)

The predominant adrenergic protoalkaloid found in the peel and fruit of bitter orange, Citrus aurantium, is synephrine. Synephrine is reputed to have thermogenic properties and is used as a dietary supplement to enhance energy and promote weight loss. However, there exists some concern that the consumption of dietary supplements containing synephrine or similar protoalkaloids may contribute to adverse cardiovascular events. This study developed and validated a positive-ion mode liquid chromatography/tandem mass spectrometry (LC/MS/MS) method for the quantitative determination of the major (synephrine) and minor (tyramine, N-methyltyramine, octopamine, and hordenine) adrenergic protoalkaloids in a suite of National Institute of Standards and Technology (NIST) bitter orange Standard Reference Materials (SRMs): SRM 3258 Bitter Orange Fruit, SRM 3259 Bitter Orange Extract, and SRM 3260 Bitter Orange Solid Oral Dosage Form. The limit of quantitation (LOQ) for all protoalkaloids is approximately 1 pg on-column, except for octopamine (20 pg on-column). Additionally, the method has a linear dynamic range of > or =3 orders of magnitude for all of the protoalkaloids. Individual, as well as "total", protoalkaloid levels (milligrams per kilogram) in the NIST SRMs were determined and compared to the levels measured by an independent liquid chromatography/fluorescence detection (LC/FD) method. Satisfactory concordance between the LC/MS/MS and LC/FD protoalkaloid measurements was demonstrated. LC/MS/MS analysis of the protoalkaloids in the SRMs resulted in mean measurement imprecision levels of < or =10% coefficient of variation (% CV).

Fast high-performance liquid chromatography analysis of phenethylamine alkaloids in Citrus natural products on a pentafluorophenylpropyl stationary phase

In this study, the chromatographic performance of a pentafluorophenylpropyl (PFPP) stationary phase was evaluated for the rapid separation of phenethylamine alkaloids (i.e. (+/-)-octopamine, (+/-)-synephrine, tyramine, N-methyltyramine and hordenine) in Citrus aurantium plant material (fruits and peel), various Citrus species, extracts and dietary supplements claiming to contain C. aurantium. The problems of phenethylamine alkaloid separation, such as peak tailing, low retention and low resolution, were successfully solved with this stationary phase. The parameters used for the method optimization included the mobile phase counter ion concentration and column temperature. A Discovery HS F5 column (150 mm x 4.6 mm i.d., 5 microm) was used, with an isocratic mobile phase composed of 10 mM ammonium acetate in 90:10 ACN-H(2)O (v/v), at a flow rate of 1.0 mL/min. The column temperature was set at 20 degrees C. The photodiode array detector monitored the eluent at 225 nm. The total analysis time was 10 min. The validation parameters, such as linearity, sensitivity, accuracy, precision and specificity, were found to be highly satisfactory. With a simple sample preparation procedure, different matrices were successfully analyzed for their alkaloid content. The results indicated that the products on sale, labeled as dietary supplements, vary widely in the quantitative composition of the active constituents: the amount of (+/-)-synephrine, the major alkaloid, in such products ranged from 0.65 to 27.41 mg/g. The other compounds were either not detected or were present at low levels. The developed method can be considered suitable for the quality control of Citrus plant material and commercial products.

Chromatographic and electrophoretic methods for the analysis of phenethylamine [corrected] alkaloids in Citrus aurantium

Citrus aurantium (bitter orange) is a plant belonging to the family Rutaceae, whose fruit extracts have been used recently for the treatment of obesity. The most important biologically active constituents of the C. aurantium fruits are phenethylamine alkaloids (i.e. octopamine, synephrine, tyramine, N-methyltyramine and hordenine). Synephrine is a primary synthesis compound with pharmacological activities such as vasoconstriction, elevation of blood pressure and relaxation of bronchial muscle. Synephrine is present in the peel and the edible part of Citrus fruit. Of the adrenergic amines of natural origin, synephrine has been found to be the main constituent of C. aurantium fruits and extracts; the other alkaloids are either absent or present in only low concentrations. It is known that synephrine and the other amines found in C. aurantium have adverse effects on the cardiovascular system, owing to adrenergic stimulation. In light of the great commercial proliferation of C. aurantium herbal medicines in recent years, this review provides an overview of various extraction, separation and detection techniques employed for the qualitative and quantitative determination of the alkaloids in C. aurantium and related species. The application of chromatographic and electrophoretic methods for the separation and determination of these active components in C. aurantium plant material and derivatives are described. Since synephrine is a chiral compound, enantioselective chromatographic and electrophoretic techniques for the analysis of synephrine enantiomers in natural products are presented. Furthermore, examples of identification of these active compounds in complex matrices by hyphenated methods, such as gas chromatography-mass spectrometry and high-performance liquid chromatography-mass spectrometry, are described. The advantages and limitations of these separation and identification methods are assessed and discussed.