Stachydrine, a Bioactive Equilibrist for Synephrine, Identified from Four Citrus Chinese Herbs.

Four Chinese herbs from the Citrus genus, namely Aurantii Fructus Immaturus (Zhishi), Aurantii Fructus (Zhiqiao), Citri Reticulatae Pericarpium Viride (Qingpi) and Citri Reticulatae Pericarpium (Chenpi), are widely used for treating various cardiovascular and gastrointestinal diseases. Many ingredients have already been identified from these herbs, and their various bioactivities provide some interpretations for the pharmacological functions of these herbs. However, the complex functions of these herbs imply undisclosed cholinergic activity. To discover some ingredients with cholinergic activity and further clarify possible reasons for the complex pharmacological functions presented by these herbs, depending on the extended structure-activity relationships of cholinergic and anti-cholinergic agents, a simple method was established here for quickly discovering possible choline analogs using a specific TLC method, and then stachydrine and choline were first identified from these Citrus herb decoctions based on their NMR and HRMS data. After this, two TLC scanning (TLCS) methods were first established for the quantitative analyses of stachydrine and choline, and the contents of the two ingredients and synephrine in 39 samples were determined using the valid TLCS and HPLC methods, respectively. The results showed that the contents of stachydrine (3.04‱) were 2.4 times greater than those of synephrine (1.25‱) in Zhiqiao and about one-third to two-thirds of those of Zhishi, Qingpi and Chenpi. Simultaneously, the contents of stachydrine, choline and synephrine in these herbs present similar decreasing trends with the delay of harvest time; e.g., those of stachydrine decrease from 5.16‱ (Zhishi) to 3.04‱ (Zhike) and from 1.98‱ (Qingpi) to 1.68‱ (Chenpi). Differently, the contents of synephrine decrease the fastest, while those of stachydrine decrease the slowest. Based on these results, compared with the pharmacological activities and pharmacokinetics reported for stachydrine and synephrine, it is indicated that stachydrine can be considered as a bioactive equilibrist for synephrine, especially in the cardio-cerebrovascular protection from these citrus herbs. Additionally, the results confirmed that stachydrine plays an important role in the pharmacological functions of these citrus herbs, especially in dual-directionally regulating the uterus, and in various beneficial effects on the cardio-cerebrovascular system, kidneys and liver.

p-Synephrine Indicates Internal Maturity of Citrus grandis (L.) Osbeck cv. Mato Peiyu-Reclaiming Functional Constituents from Nonedible Parts.

The processing of Citrus grandis Osbeck cv. Mato Peiyu (CGMP) fruits generates a considerable amount of waste, mainly the flavedo, albedo, and segment membrane; the generated waste yields severe environmental and economic challenges. In this study, we tried to reclaim some functional chemicals from the waste. Our data indicated that the essential oil content in the flavedo was 0.76-1.34%, with the major component being monoterpenes (93.75% in August, declining to 85.56% in November, including mainly limonene (87.08% to 81.12%) and others such as ß-myrcene). p-Synephrine (mg/100 g dry weight) declined accordingly (flavedo, 10.40 to 2.00; albedo, 1.80 to 0.25; segment membrane, 0.3 in August, 0.2 in September, and none since October). Polyphenols (in µg/g) included gallic acid (70.32-110.25, 99.27-252.89, and 105.78-187.36, respectively); protocatechuic acid (65.32-204.94, 26.35-72.35, and 214.98-302.65, respectively), p-coumaric acid (30.63-169.13, 4.32-17.00, and 6.68-34.32, respectively), ferulic acid (12.36-39.36, 1.21-10.25, and 17.07-39.63, respectively), and chlorogenic acid (59.19-199.36, 33.08-108.57, and 65.32-150.14, respectively). Flavonoids (in µg/g) included naringin (flavedo, 89.32-283.19), quercetin (181.05-248.51), nobiletin (259.75-563.7), hesperidin, and diosmin. The phytosterol content (mg/100 g) was 12.50-44.00 in the flavedo. The total dietary fiber in the segment membrane was 57 g/100 g. The antioxidant activity against the DPPH• and ABTS+• free radicals was moderately high. In conclusion, the waste of CGMP fruits is worth reclaiming for essential oil, p-synephrine, polyphenolics, and dietary fiber. Notably, p-synephrine content (flavedo: <8 mg/100 g dry weight, albedo: <2.0, or segment membrane: <0.4 mg) can serve as a marker of the internal maturation of CGMP fruits.

Racemic synephrine found in Citrus aurantium-listing pre-workout supplements suggests a non-plant-based origin.

Multi-ingredient pre-workout supplements (MIPS) contain Citrus aurantium as a source of bioactive amines such as p-synephrine, but concerns regarding the authenticity of ingredients in some supplements as well as adverse effects from consumption have been raised. R-(-)-Synephrine is the predominant enantiomer in Citrus aurantium extracts while synthetic preparations are often racemic. The aims of this study were to develop a screening method to determine the ratio of synephrine enantiomers in pre-workout supplements listing Citrus aurantium and to assess the ingredient authenticity by directly comparing their ratios to that found in Citrus aurantium standardised reference materials (SRMs). Quantification of enantiomers in the supplements and SRMs was achieved using a validated, high-performance liquid chromatography-single quadrupole mass spectrometry (HPLC-UV-QDa) direct enantioseparation method with a cellobiohydrolase (CBH) column (100 × 4.0 mm, 5 µM) and UV detection at 225 nm. Citrus aurantium SRMs were found to have an average enantiomeric ratio of 94:6 (R:S) with total synephrine ranging from 5.7 to 90.2 mg/g. Within the pilot sample of pre-workout supplements tested, only 42% (5/12) had enantiomeric ratios consistent with the SRMs with total synephrine ranging from 0.03 to 91.2 mg/g. For the remaining supplements, four had racemic ratios of synephrine (0.14 to 5.4 mg/g), two lacked any detectable levels of synephrine, and one had solely the S-(+)-enantiomer (0.15 mg/g). These results bring the authenticity of labelling of some pre-workout supplements into question and highlight the need for more stringent labelling regulations and testing for dietary supplements.

The determination of common anabolic steroid and stimulants in nutritional supplements by HPLC-DAD and LC-MS.

A high-performance liquid chromatography method employing a diode-array detector and mass spectrometry detector was developed, validated and implemented for determining Synephrine, Caffeine, Clenbuterol, Nandrolone, Testosterone and Methylhexaneamine in Nutritional supplements. The use of Nutritional supplements is widespread. Hazards relating to concentration, composition, individual contaminants, supplements interactions as well as positive doping results among athletes present increasing concerns regarding nutritional supplement consuming. The proposed method was validated according to the International Conference on the Harmonization of the Technical Requirements for Registration of Pharmaceuticals for Human Use (ICH) standards. The proposed method observed to be accurate, linear, precise, sensitive, required minimal sample preparation and uncomplicated mobile phase. The implementation of the proposed method on nine commercial supplements shows that inaccurate labeling for some supplements regarding the concentration of the ingredients.

Identification and determination of chemical constituents of Citrus reticulata semen through ultra high performance liquid chromatography combined with Q Exactive Orbitrap tandem mass spectrometry.

Citrus reticulata semen, a traditional Chinese medicinal material, has desirable medicinal and dietary properties. In this study, a method combining ultra high performance liquid chromatography with Q Exactive Orbitrap tandem mass spectrometry was established and validated for the identification and analysis of the chemical components of C. reticulata semen for the first time. The evaluation of different retention times and fragmentation characteristics, as well as comparative analysis with the literature, resulted in the identification of 35 chemical constituents, including 21 flavonoids and 14 other compounds. The 21 flavonoids derived from C. reticulata semen were reported for the first time. Seven of the chemical components of C. reticulata semen were quantitatively analyzed using the developed method under the optimal conditions. The results showed that the content of limonin, hesperidin, nobiletin, synephrine, tangeretin, 3,5,6,7,8,3',4'-heptamethoxyflavone and 5-hydroxide-6,7,8,3',4'-pentamethoxyflavone in C. reticulata semen was 11.1666, 0.0404, 0.0092, 0.0255, 0.0087, 0.0010, and 0.0008 mg/g, respectively. This study demonstrated that the ultra high performance liquid chromatography Q Exactive Orbitrap mass spectrometry based method can be used to rapidly and reliably analyze the chemical constituents of C. reticulata semen. These results provide a scientific basis for further studies of C. reticulata semen.

Identification and Comparison of Constituents of Aurantii Fructus and Aurantii Fructus Immaturus by UFLC-DAD-Triple TOF-MS/MS.

Although Aurantii Fructus (AF) and Aurantii Fructus Immaturus (AFI) are both the fruits of the same rutaceae plant at different stages of growth, they exert similar yet distinct clinical effects. The chemical composition is crucial for quality control as well as therapeutic application. To address this concern, it is significant to evaluate the similarities and differences of the constituents in both AF and AFI. The extract of AF and AFI were comprehensively analyzed by ultra fast liquid chromatography-photodiode array detector-triple-time of flight-tandem mass spectrometry (UFLC-DAD-Triple TOF-MS/MS). Among the 40 compounds detected, 19 metabolites were detected in both the AF and AFI; whereas 13 compounds were only detected in AF and five constituents were exclusively detected in AFI. In particular, even in AFI, three compounds were only identified in AFI (Citrus aurantium' L. and its cultivar). Among the 18 compounds confirmed by standard database, 13 compounds were reported in AF and AFI for the first time. Furthermore, the distinction was also revealed by the content of naringin, hesperidin, neohesperidin, and synephrine. The study directly contributed to the similarities and differences of AF and AFI. Herein, similarities and the differences in chemical profiles of AF and AFI could explain the current clinical applications.

Determination of synephrine in feeds by a novel quick, easy, cheap, effective, rugged, and safe solid-phase extraction method combined with UHPLC-MS/MS.

To detect and quantify synephrine in feed, an effective analytical method based on quick, easy, cheap, effective, rugged, and safe solid-phase extraction coupled to ultra high performance liquid chromatography with tandem mass spectrometry was developed with isotopic internal standards. Pretreatment was performed using quick, easy, cheap, effective, rugged, and safe solid-phase extraction with primary secondary amine and C18 sorbent as sorbents in combination with Oasis MCX column clean-up to extract and purify feed samples. Tandem mass spectrometry detection in positive ion mode was conducted in positive multiple reaction monitoring mode in addition to the quantitative internal standard method. Two transitions of synephrine at m/z 168.1/150.0 and 168.1/135.0 were selected, and m/z 168.1/135.0 was determined as the quantification ion pair. D9 -Terbutaline was selected as an internal standard, for which m/z 235.1/153.0 was selected as the quantification ion pair. Good linearity was shown for synephrine in the range of 0.5-50 µg/L, and the correlation coefficient exceeded 0.999. The recoveries in three different feed samples at three spiked levels were 81.42-112.08%, and the relative standard deviations were not greater than 14.66%. The method proposed in this study was reliable and highly effective, and its sensitivity, accuracy, and precision are suitable for determining synephrine residues in feed samples.

Synephrine - A potential biomarker for orange honey authenticity.

A LC-MS/MS method for synephrine as a biomarker for orange honey authenticity was developed and validated. The sample was extracted with 5% TCA and cleaned up with Florisil providing 83.7% recoveries. Ions transitions for quantification and identification were 168→135.0 and 168→107.0, respectively. The limits of detection and quantification were 0.66 and 1.0ng/g, respectively. Synephrine was detected in orange honey at levels from 79.2 to 432.2ng/g, but not in other monofloral honeys. It was also present in some wildflower honeys (9.4-236.5ng/g), showing contribution of citrus to this polyfloral honey. Results were confirmed by qualitative pollen analysis. No citrus pollen was detected in honey containing synephrine levels ≤43.8ng/g, suggesting that synephrine in honey is more sensitive compared to pollen analysis. Synephrine was found in citrus but not in other apiculture flowers. Therefore, synephrine is a botanical marker to differentiate and attest authenticity of orange honey.

Pharmaceutical doses of the banned stimulant oxilofrine found in dietary supplements sold in the USA.

Oxilofrine (4-[1-hydroxy-2-(methylamino)propyl]phenol) is a pharmaceutical stimulant prescribed in dosages of 16 to 40 mg to stimulate the heart and increase blood pressure. It has never been approved for use in the USA as a prescription drug or as a dietary supplement. Several athletes, however, have been banned from sport for testing positive for oxilofrine and have claimed that they inadvertently consumed oxilofrine in sports supplements. Consumption of supplements containing oxilofrine may also pose serious health risks. For example, one brand of supplements containing oxilofrine has been linked to serious adverse events including vomiting, agitation, and cardiac arrest. We designed our study to determine the presence and quantity of oxilofrine in dietary supplements sold in the USA. A validated ultra-high performance liquid chromatography-quadrupole time of flight-mass spectrometry method was developed for the identification and quantification of oxilofrine. The separation was achieved using a reversed phase column, mass spectrometry detection, and a water/acetonitrile gradient as the mobile phase. The presence of oxilofrine was confirmed using a reference standard. We analyzed 27 brands of supplements labelled as containing a synonym of oxilofrine ('methylsynephrine') and found that oxilofrine was present in 14 different brands (52%) at dosages ranging from 0.0003 to 75 mg per individual serving. Of the supplements containing oxilofrine, 43% (6/14) contained pharmaceutical or greater dosages of oxilofrine. Following instructions on the label, consumers could ingest as much as 250 mg of oxilofrine per day. The drug oxilofrine was found in pharmacological and greater dosages in supplements labelled as containing methylsynephrine. Copyright © 2016 John Wiley & Sons, Ltd.

Comparison of Aurantii Fructus Immaturus and Aurantii Fructus based on multiple chromatographic analysis and chemometrics methods.

To get a better understanding of the bioactive constituents in Aurantii Fructus Immaturus (AFI) and Aurantii Fructus (AF), in the present study, a comprehensive strategy integrating multiple chromatographic analysis and chemometrics methods was firstly proposed. Based on segmental monitoring, a high-performance liquid chromatography (HPLC)-variable wavelength detection method was established for simultaneous quantification of ten major flavonoids, and the quantitative data were further analyzed by hierarchical cluster analysis (HCA) and principal component analysis (PCA). A strong cation exchange-high performance liquid chromatography (SCX-HPLC) method combined with t-test and one-way analysis of variance (ANOVA) was developed to determine synephrine, the major alkaloid in AFI and AF. The essential oils were analyzed by gas chromatography-mass spectrometry (GC-MS) and further processed by partial least squares discrimination analysis (PLS-DA). The results indicated that the contents of ten flavonoids and synephrine in AFI were significantly higher than those in AF, and significant difference existed in samples from different geographical origins. Also, 9 differential volatile constituents detected could be used as chemical markers for discrimination of AFI and AF. Collectively, the proposed comprehensive analysis might be a well-acceptable strategy to evaluate the quality of traditional citrus herbs.

Variability of Stimulant Levels in Nine Sports Supplements Over a 9-Month Period.

Many studies have found that some dietary supplement product labels do not accurately reflect the actual ingredients. However, studies have not been performed to determine if ingredients in the same dietary supplement product vary over time. The objective of this study was to assess the consistency of stimulant ingredients in popular sports supplements sold in the United States over a 9-month period. Three samples of nine popular sports supplements were purchased over the 9-month period. The 27 samples were analyzed for caffeine and several other stimulants (including adulterants). The identity and quantity of stimulants were compared with stimulants listed on the label and stimulants found at earlier time points to determine the variability in individual products over the 9-month period. The primary outcome measure was the variability of stimulant amounts in the products examined. Many supplements did not contain the same number and quantity of stimulants at all time points over the 9-month period. Caffeine content varied widely in five of the six caffeinated supplements compared with the initial measurement (-7% to +266%). In addition, the stimulants-synephrine, octopamine, cathine, ephedrine, pseudoephedrine, strychnine, and methylephedrine-occurred in variable amounts in eight of the nine products. The significance of these findings is uncertain: the sample size was insufficient to support statistical analysis. In our sample of nine popular sports supplements, the presence and quantity of stimulants varied over a 9-month period. However, future studies are warranted to determine if the variability found is significant and generalizable to other supplements.

3D-printed and CNC milled flow-cells for chemiluminescence detection.

Herein we explore modern fabrication techniques for the development of chemiluminescence detection flow-cells with features not attainable using the traditional coiled tubing approach. This includes the first 3D-printed chemiluminescence flow-cells, and a milled flow-cell designed to split the analyte stream into two separate detection zones within the same polymer chip. The flow-cells are compared to conventional detection systems using flow injection analysis (FIA) and high performance liquid chromatography (HPLC), with the fast chemiluminescence reactions of an acidic potassium permanganate reagent with morphine and a series of adrenergic phenolic amines.

Determination of synephrine and octopamine in bitter orange peel by HPTLC with densitometry.

This paper presents the development and validation of an improved method for the simultaneous analysis of synephrine and octopamine using high-performance thin-layer chromatography with densitometric detection. Separation was performed on silica gel 60F254 plates. The mobile phase is comprised of methanol, ethylacetate, methylene chloride and concentrated ammonia (2:2:1:0.05, v:v:v:v). The Rf values were 0.292 ± 0.0083 and 0.413 ± 0.0089 for synephrine and octopamine, respectively (n = 9). Ultraviolet absorbance detection at 277 nm was used for the alkaloids detection. Specificity, accuracy (recovery rates were between 96 and 99%) and precision (in both cases intra-day precision and inter-day precision were ≤ 2.0%) of the method were determined. Their amounts were calculated using the regression equations of the calibration curves which were linear in the range 0.2-1.2 µg/spot. The amounts of alkaloids in basic methanolic extracts of bitter orange peel measured by the method were 0.253 and 0.142% for synephrine and octopamine, respectively. Most of the factors evaluated in the robustness test were found to have an insignificant effect on the selected responses at 95% confidence level. The method was validated giving rise to a dependable and high-throughput procedure well suited to routine application.

[Determination of the active constituents in aurantii fructus from Jiangxi province at different harvest time by HPLC].

OBJECTIVE: To determine the contents of the main active constituents in Aurantii Fructus from Jiangxi at different harvest time and make sure the best harvest time. METHODS: RP-HPLC was used to assay the active constituents (including naringin, neohesperidin, synephrine, nobiletin, tangeretin, meranzin hydrate, meranzin, marmin and auraptene) contents in the Aurantii Fructus at different harvest periods from Xingan and Zhangshu countries. RESULTS: The trend of the contents of those active constituents was basically decreased as the day trailing. CONCLUSION: The best harvest time of Aurantii Fructus from Jiangxi is about the Great Heat.

Phytochemical profile and antioxidant activity of physiological drop of citrus fruits.

UNLABELLED: The phytochemical content and the antioxidant activity (AA) of physiological drop of the main citrus species grown in China were investigated. Among the flavonoids, hesperidin was found mostly in mandarin and sweet orange, naringin was found mostly in sour orange, pummelo, grapefruit and a hybrid (Gaocheng), narirutin was found in most varieties, neohesperidin was found in Gaocheng and Huyou, and nobiletin and tangeretin were found in most varieties. Hydroxycinnamic acids were the main phenolic acids present, ferulic acid and caffeic acid were the dominant in most cases. There was a greater amount of free (extractable) than bound (insoluble) phenolic acids. Levels of limonoids were higher in Foyou, Eureka lemon, and Gaocheng than those in the other cultivars. The highest level of synephrine was found in Ponkan and Weizhang Satsuma. AA was highest in Ponkan and Weizhang Satsuma and lowest in Huyou, pummel, and lemon. These results suggest that physiological drop of citrus fruits have good potential as sources of different bioactive compounds and antioxidants. PRACTICAL APPLICATION: Physiological drop of citrus fruits may be a good resource of bioactive compounds including flavonoids, phenolic acids, limonoids, synephrine, and a good material of nutraceuticals.

[Determination of synephrine and arecoline contents in Xiao'er Xiaoji Zhike oral liquid].

OBJECTIVE: To develop a HPLC method for the determination of synephrine and arecoline contents in Xiao'er Xiaoji Zhike oral liquid. METHOD: The analysis was performed on a Symmetry C18 column (4.6 mm x 250 mm, 5 microm) eluted with acetonitrile-methanol-0.1% acetic acid solution (containing potassium dihydrogen phosphate 0.6 g and SDS 1.0 g per 1 000 mL) (15: 30: 55) as mobile phase. The detection wavelength was set at 215 nm. RESULT: The synephrine and arecoline concentrations had good linear relationship between 0.281 5-2.815 and 0.040 16-0.401 6 microg (r > 0.999 7), and the average recoveries of the two compounds were 97.1% (RSD 1.4%) and 100% (RSD 1.3%), respectively. CONCLUSION: The method is simple, accurate and sensitive.

Development and validation of a GC/IT-MS method for simultaneous quantitation of para and meta-synephrine in biological samples.

After the FDA's ban of ephedrine-containing supplements, Citrus aurantium appeared as an alternative to ephedra in herbal weight loss products. Synephrine, the most abundant active component of C. aurantium, exists in three different structural or positional isomeric forms (ortho-o-, meta-m-, and para-p-). Dietary supplements contain m- and p-synephrine, both alpha-adrenergic agonists,while the m-isoform is the most potent at alpha(1)-adrenoreceptors. In spite of the pharmacokinetic and toxicological interest in the study of these compounds, adequate methods for their quantification in biological samples are yet to be developed. Thus, in the present study, a sensitive gas chromatography-ion trap mass spectrometry (GC/IT-MS) method was developed and validated for the simultaneous quantitation of m- and p-synephrine in a cellular matrix after solid phase extraction (SPE). The validation of the method was performed through the evaluation of the following parameters: selectivity, linearity, specificity, precision, accuracy, limit of detection, limit of quantification, and recovery. The method's applicability was studied in two different biological matrices by evaluating p- and m-synephrine uptake in Caco-2 cells and also in freshly isolated cardiomyocytes from adult rat. The developed GC/IT-MS method was shown to be selective, accurate, precise, and valid for simultaneous determination of p- and m-synephrine in biological samples.

Analysis of synephrine in da-cheng-qi decoction by HPLC employing precolumn derivatization with 9-fluorenylmethyl chloroformate.

A sensitive and reliable method has been developed to determine synephrine in a famous purgative Chinese medicinal prescription, da-cheng-qi decoction. After purified by solid-phase extraction (SPE), the decoction was derivatized with 9-fluorenylmethyl chloroformate in borate buffer and analyzed by reversed-phase high-performance liquid chromatography equipped with a diode-array detector. The chromatographic separation was carried out on a Shimadzu shim-pack VP-ODS column using acetonitrile-water as mobile phase. This method was validated in terms of linearity, recovery, precision, accuracy, and repeatability. Calibration curves were linear (r(2) > 0.99) over the concentration range of 0.78-100 microg/mL, and the mean recovery was 93.28%. The intra- and inter-batch precisions were less than 2% in terms of relative standard deviations. The accuracy and repeatability were well within the acceptable range. The limit of detection was 0.25 microg/mL. This validated method also can be used for assays of herbal products, fruits, dietary supplements, and biological samples containing synephrine.

Selectivity and potential interference from phenolic compounds in chemiluminescence methods for the determination of synephrine.

Three recently reported chemiluminescence methods (based on reactions with alkaline luminol and hexacyanoferrate(III); acidic cerium(IV) and rhodamine B; and acidic permanganate with polyphosphates) for the determination of synephrine were re-evaluated in terms of their selectivity towards this analyte in comparison to other phenolic compounds. A fourth reagent system, acidic soluble manganese(IV) and formaldehyde, was also examined. Each set of reagents was sensitive towards synephrine (limits of detection were 3 x 10(-9), 5 x 10(-8), 1 x 10(-8) and 1 x 10(-8) mol/L, respectively) but also responded with numerous other phenolic compounds, including some that are present in citrus fruit extracts, dietary supplements and/or biological fluids. It is therefore recommended that the determination of synephrine in these matrices should incorporate physical separation of sample components (e.g. chromatography or electrophoresis). In more general terms, this study illustrates that accurate percentage recoveries for an analyte in spiked samples (without validation against another analytical method) are insufficient to confirm the analytical utility of new flow-injection analysis (FIA) procedures.

Synephrine content of juice from Satsuma mandarins (Citrus unshiu Marcovitch).

Synephrine, the main protoalkaloid in Citrus species, is commonly analyzed as the active component in citrus peel-containing herbal supplements, but the edible parts of mandarins have been largely ignored. The synephrine concentration has been determined in the juices of Citrus unshiu mandarins harvested from 10 different groves located in a major growing region in California. For comparison, the physicochemical properties of the juices, including pH, conductivity, soluble solids content, and titratable acidity, were also measured. The synephrine values among 10 groves ranged from 73.3 to 158.1 mg L (-1). Repeat sampling of fruit from the 10 locations showed that the intragrove variability in synephrine concentrations ranged from 1.0 to 27.7% CV and was grove dependent. Among the physicochemical properties, titratable acidity weakly correlated with synephrine, and for one sample a low maturity index was linked to high synephrine content. The overall mean synephrine concentration of 92.8 mg L (-1) is up to 6-fold higher than values previously determined for orange juices and suggests that mandarin juice could constitute a significant dietary source of synephrine. Furthermore, the results suggest that grove location and maturity affect synephrine content.