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At least 19 recordsLinked to original sources
PubMed1996

Determination of synephrine enantiomers in food and conjugated synephrine in urine by high-performance liquid chromatography with electrochemical detection.

Determination of synephrine enantiomers was made with HPLC with electrochemical detection using a chiral ligand-exchange column (Sumichiral OA-6000). The calibration curve for each enantiomer showed good linearity (r = 0.999) at 1.0-500 pmol injected with a detection limit of 1.0 pmol (signal-to-noise ratio (S/N) = 3). Relative standard deviation (RSD) was 1.8% at 50 pmol d-synephrine and 1.6% at 50 pmol l-synephrine. The contents of synephrine enantiomer in food such as Citrus unshiu fruit, orange juice, and marmalade were determined. The present method was also used to determine conjugated synephrine enantiomers in urine following the ingestion of C. unshiu pulp. l-Synephrine in fruit was converted to the conjugated form of synephrine, and l-synephrine underwent chiral inversion to d-synephrine in vivo.

Adult↗
PubMed1988

Activities of octopamine and synephrine stereoisomers on alpha-adrenoceptors.

1. The activities of the (-)- and (+)-forms of m- and p-octopamine and m- and p-synephrine on alpha 1-adrenoceptors from rat aorta and anococcygeus and alpha 2-adrenoceptors from rabbit saphenous vein were compared with those of noradrenaline (NA). 2. The rank order of potency of the (-)-forms on alpha 1-adrenoceptors from rat aorta and alpha 2-adrenoceptors was NA greater than m-octopamine = m-synephrine greater than p-octopamine = p-synephrine. The two m-compounds were 6 fold less active than NA on alpha 1-adrenoceptors from rat aorta and 150 fold less active on alpha 2-adrenoceptors. The two p- compounds were 1,000 fold less active than NA on both alpha 1-adrenoceptors from rat aorta and alpha 2-adrenoceptors. The rank order of potency of the (-)- forms on alpha 1-adrenoceptors from rat anococcygeus was NA = m-synephrine greater than m-octopamine greater than p-octopamine = p-synephrine. m-Octopamine was 4 fold less active than NA and (-)-m-synephrine. The two p- compounds were 30 fold less active than NA. 3. The rank order of potency of the (+)- forms was NA greater than m-octopamine greater than m-synephrine greater than p-octopamine greater than p-synephrine on both alpha 1- and alpha 2-adrenoceptors. The potency of each (+)- form was 1-2 orders of magnitude less than that of the (-) counterpart, the differences being greater for the stereoisomers of synephrine than for those of octopamine on both alpha 1- and alpha 2-adrenoceptors. 4. The yohimbine diastereoisomer antagonists, rauwolscine and corynanthine, were tested against (-)-NA and (-)-m-octopamine-induced contractions in both preparations. Based upon the known selectivities of these isomers for alpha-adrenoceptor subtypes, it is concluded that the rat aorta contains only alpha 1-adrenoceptors while the rabbit saphenous vein possesses predominantly alpha 2-adrenoceptors. 5. Ligand binding data for the octopamine and synephrine stereoisomers at alpha 1- and alpha 2-binding sites from rat cerebral cortex was also obtained. (-)-Forms were more active than (+)-forms. The rank order of affinity of the (-)-forms for both alpha 1- and alpha 2-binding sites was NA greater than m-octopamine = m-synephrine greater than p-synephrine greater than p-octopamine. The relative affinities of the members of the series against alpha 1-binding sites were very similar to their relative functional activities on rat aorta. However, the affinities of both m- and p-compounds relative to that of ( -)-NA were much greater at the x2-binding sites than were the relative activities in rabbit saphenous vein, possibly suggesting low intrinsic efficacy. Functional antagonist responses to NA by the (-)-octopamine and synephrines could not, however, be demonstrated on rat aorta or rabbit saphenous vein. 6. The activities of m-octopamine and m-synephrine were not significantly different from each other on either a,-adrenoceptors from rat aorta or x2-adrenoceptors; however, m-synephrine is more active than m-octopamine on a,-adrenoceptors from rat anococcygeus. Both m-octopamine and msynephrine can be considered to be naturally occurring x,-selective amines. However, if m- and poctopamine are co-released with NA in amounts proportional to their concentration, it is concluded that their activities on m,- and x2-adrenoceptors are too low to be physiologically significant.

2-Hydroxyphenethylamine↗
PubMed2001

Characterization of antidepressant-like effects of p-synephrine stereoisomers.

We previously reported that p-synephrine has antidepressant-like activity in the murine models of forced swimming and tail suspension. In the present study, we characterized antidepressant-like effects of p-synephrine stereoisomers in both in vivo and in vitro systems. In the tail suspension test, S-(+)-p-synephrine (3 mg/kg, p.o.) reduced the duration of immobility, while R-(-)-p-synephrine (0.3-3 mg/kg, p.o.) had no effect. S-(+)-p-synephrine (0.3, 1 and 3 mg/kg, p.o.) and R-(-)-p-synephrine (1 mg/ kg and 3 mg/kg, p.o.) significantly reversed the reserpine (2.5 mg/kg, i.p.)-induced hypothermia. S-(+)-p-synephrine was more effective than R-(-)-p-synephrine in inhibition of both [3H]noradrenaline uptake in rat cerebral cortical slices (maximal inhibition 85.7 +/- 7.8% vs. 59.8 +/- 4.3%; EC50 5.8 +/- 0.7 microM vs. 13.5 +/- 1.2 microM) and [3H]nisoxetine binding (Ki 4.5 +/- 0.5 microM vs. 8.2 +/- 0.7 microM). In contrast, R-(-)-p-synephrine was more effective than S-(+)-p-synephrine in stimulation of [3H]noradrenaline release from rat cerebral cortical slices (maximal stimulation 23.9 +/- 1.8% vs. 20.1 +/- 1.7%; EC50 8.2 +/- 0.6 microM vs. EC50 12.3 +/- 0.9 microM). The stimulatory effect of R-(-)-p-synephrine on [3H]noradrenaline release was inhibited by nisoxetine (100 nM), but tetrodotoxin (1 microM) and elimination of extracellular calcium had no effect. It is suggested that S-(+)-p-synephrine has more effective antidepressant-like activity than R-(-)-p-synephrine.

Adrenergic Uptake Inhibitors↗
PubMed2005

Exactly which synephrine alkaloids does Citrus aurantium (bitter orange) contain?

Following the withdrawal of ephedrine from the dietary supplement marketplace sales of products containing Citrus aurantium (CA) (bitter orange) for weight loss are believed to have increased dramatically. CA contains a number of constituents speculated to lead to weight loss, of which the most frequently cited constituent is synephrine. Concerns have been raised about the safety of products containing synephrine. To develop an adequate basis for clinical and public health recommendations, it is necessary to understand the nature of the synephrine alkaloids in CA. There are six possible isomers of synephrine (para, meta, ortho; and for each a d or l form). Some authors have stated that CA contains only p-synephrine, whereas other authors have stated that CA contains m-synephrine. This is an important distinction because the two molecules have different pharmacologic properties, which may differentially affect safety and efficacy. We are unable to identify published data that explicitly show whether CA contains p-synephrine, m-synephrine, or both. In this brief report, we show that at least one product purportedly containing synephrine alkaloids from CA contains both p-synephrine and m-synephrine. We believe this justifies further investigation into which synephrine alkaloids are present in CA and products purportedly containing synephrine alkaloids from CA and the relative quantities of each of the different isomers.

Alkaloids↗
PubMed1988

Activities of octopamine and synephrine stereoisomers on octopaminergic receptor subtypes in locust skeletal muscle.

The activities of the (-) and (+)- forms of p-, m- and o-octopamine and p- and m-synephrine have been compared on the different subtypes of octopamine receptor present in the extensor-tibiae neuromuscular preparation from the locust hindleg. The rank order of potency of the (-)-forms on the OCTOPAMINE2A receptors was p-synephrine greater than p-octopamine greater than m-octopamine greater than o-octopamine greater than m-synephrine whilst the rank order of the (+)-forms was p-synephrine greater than p-octopamine greater than m-octopamine. (+)-m-Synephrine and (+)-o-octopamine had no effect on this class of receptor when tested up to a concentration of 10(-3) M. The rank order of potency of the (-)-forms on the OCTOPAMINE2B receptors was p-synephrine greater than p-octopamine greater than m-synephrine greater than m-octopamine greater than o-octopamine whilst the rank order of the (+)-forms was p-octopamine greater than p-synephrine greater than m-octopamine greater than o-octopamine. (+)-m-Synephrine again had no effect up to a concentration of 10(-3) M. The rank order of potency of the (-)-forms on the OCTOPAMINE1 receptors was p-synephrine greater than p-octopamine greater than m-synephrine greater than m-octopamine greater than o-octopamine, whilst the rank order of the (+)-forms was p-synephrine greater than p-octopamine greater than o-octopamine greater than m-synephrine greater than m-octopamine.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed2005

Enantioselective LC analysis of synephrine in natural products on a protein-based chiral stationary phase.

An enantioselective LC method with photodiode array detection (PAD) was developed for the enantioseparation of (+/-)-synephrine from C. aurantium L. var. amara fruits and phytotherapic derivatives by using a protein-based chiral stationary phase with cellobiohydrolase as the chiral selector (Chiral-CBH). Analyses were carried out on a Chiral-CBH column (100x4.0 mm i.d., 5 microm), with a mobile phase consisting of 2-propanol (5%, w/w) in sodium phosphate buffer (pH 6.0; 10 mM) and disodium EDTA (50 microM). The flow rate was 0.8 mL/min. Detection was set at 225 nm. To identify the order of elution, the racemate was resolved by the preparation of suitable diastereoisomeric salts with antipodes of appropriate organic acids. Isolation of synephrine from C. aurantium fruits and phytoproducts was performed by solid-phase extraction (SPE) with a strong cation-exchange phase. The method developed was validated and was found to be linear in the 0.40-40.14 microg/mL range (r2=1.000, P<0.0001) for both synephrine enantiomers. The limit of detection (LOD) for each enantiomer was 0.04 microg/mL. The limit of quantification (LOQ) for each enantiomer was 0.13 microg/mL. Intra-day precision (calculated as %R.S.D.) ranged from 0.03 to 0.24% for (-)-synephrine and from 0.03 to 0.35% for (+)-synephrine. Inter-day precision (calculated as %R.S.D.) ranged from 0.07 to 1.45% for (-)-synephrine and from 0.06 to 1.26% for (+)-synephrine. Intra- and inter-day accuracies (calculated as %recovery) were in the ranges of 97.4-100.6 and 98.0-101.6% for (-)-synephrine, and in the ranges 97.0-101.5 and 98.1-102.8% for (+)-synephrine. The results of the application of the method to the analysis of C. aurantium samples showed that (-)-synephrine was the main component. (+)-Synephrine was not detected in C. aurantium fruits and was present in low concentration in the phytoproducts.

Biological Products↗
PubMed1983

The mammalian metabolism of R-(-)-m-synephrine.

The metabolism of R-(-)-m-synephrine (administered orally and by inhalation in man and intraperitoneally in rats) was studied quantitatively by a gas chromatography-mass spectrometry-selected ion monitoring (g.c.-m.s.-s.i.m.) method using deuterated internal standards. When m-synephrine hydrochloride was administered orally to humans in normal dosage regimens four main metabolites were excreted in urine: (i) unconjugated m-hydroxymandelic acid (MHMA, 30%), (ii) m-hydroxyphenylglycol (MHPG) sulphate (6%), (iii) m-synephrine sulphate (47%) and (iv) m-synephrine glucuronide (12%). The comparable figures after inhalation of the drug were 24, 6, 56 and 5%. Intraperitoneal injection of m-synephrine into rats gave: unconjugated MHMA (5%), MHPG sulphate (35%), unconjugated m-synephrine (7%) and conjugates of m-synephrine (9%:4% as the glucuronide and 5% as the sulphate).

Administration, Oral↗
PubMed2001

Hemodynamic effects of synephrine treatment in portal hypertensive rats.

Synephrine, a sympathomimetic alpha1-adrenoceptor agonist, has been shown to induce dose-dependent portal hypotensive effects after acute intravenous infusion. The present study was undertaken to investigate the hemodynamic effects of 8-day administration of synephrine in portal hypertensive rats. Portal hypertension was induced by either partial portal vein ligation (PVL) or bile duct ligation (BDL). Portal hypertensive rats were allocated into one of two groups: vehicle group (0.1 N HCl, 0.5 ml/12 h) or synephrine group (1 mg/kg per 12 h), with 7 rats in each group. Synephrine or vehicle was administered by gavage into PVL and BDL rats for 8 consecutive days. Systemic as well as splanchnic hemodynamic parameters were measured thereafter. Synephrine significantly ameliorated the hyperdynamic state in both PVL and BDL rats. The portal venous pressure in PVL and BDL rats (-13.5% and -10.1%, respectively), portal tributary blood flow (-19.5% and -20.4%) and cardiac index (-12.1% and -18.8%) were significantly reduced, while mean arterial pressure (10.4% and 23.4%) and systemic (26.3% and 51.0%) as well as portal territory (47.1% and 67.7%) vascular resistance were enhanced by treatment of synephrine as compared with vehicle treatment. Our results showed that eight-day administration of synephrine exerted beneficial hemodynamic effects in two models of portal hypertensive rats.

Adrenergic alpha-Agonists↗
PubMedDate not supplied

Sensitive determination of synephrine by flow-injection chemiluminescence.

It was found that light emission produced by the oxidation of luminol by potassium ferricyanide in basic medium was enhanced by synephrine, an anti-obesity drug. The optimum conditions for this chemiluminescent reaction were studied in detail in a flow injection system and employed in a new, simple and rapid method for the determination of synephrine. A mechanism for this reaction is proposed, based on the chemiluminescence reaction spectra. In the optimum conditions, CL intensity is proportional to concentration of synephrine in the 0.008-1 microg/mL range. The limit of detection is 1.6 ng/mL for synephrine (3sigma), and the relative standard deviation (n = 11) is 2.6% for 0.5 microg/mL synephrine. The method was applied to the determination of synephrine in herbal products, citrus fruit and biological fluids. The recoveries were satisfactory (90-102%). The results given by the proposed method are in good agreement with those given by HPLC-UV.

Chromatography, High Pressure Liquid↗
PubMed2005

A rapid liquid chromatography electrospray ionization mass spectrometry(n) method for evaluation of synephrine in Citrus aurantium L. samples.

Immature bitter orange fruit and its extracts have been introduced into the market as an alternative to Ephedra in weight loss products. However, the safety of the immature bitter orange fruit and its extracts is a debated argument due to the presence of synephrine, a constituent known as a sympathomimetic agent. In this paper, we describe the development of a new, rapid, and simple liquid chromatography-electrospray ionization-tandem mass spectrometry method devoted to the quantitative determination of synephrine in bitter orange samples, containing a high quantity of synephrine, and sweet orange samples, known to contain a low level of synephrine but at the same time being one of the main synephrine sources in a normal human diet. Two bitter orange dry extracts containing 5 and 6% sSynephrine and 10 sweet orange samples have been analyzed. Between the sweet orange samples, six were fresh oranges and four were fresh-squeezed juices; in these samples, the synephrine levels ranged from 0.00128 to 0.00349%.

Beverages↗
PubMed1983

The metabolism and biosynthesis of (+/-)-o-octopamine and (+/-)-o-synephrine in the rat.

The metabolism of (+/-)-o-octopamine and (+/-)-o-synephrine by rats was studied quantitatively by a gas chromatography-mass spectrometry-selected ion monitoring (g.c.-m.s.-s.i.m.) method using deuterated internal standards. When o-octopamine was injected intraperitoneally into rats four metabolites were excreted in the urine: (i) unconjugated o-hydroxymandelic acid (OHMA) (16%), (ii) unconjugated o-hydroxyphenylglycol (OHPG) (4.5%), (iii) an acid-hydrolysable conjugate of OHPG (28%) and (iv) unconjugated o-octopamine (10%). When o-synephrine benzoate was similarly administered six metabolites were excreted in urine: (i) unconjugated OHMA (13.5%), (ii) unconjugated OHPG (3.3%), (iii) an acid-hydrolysable conjugate of OHPG (15.6%), (iv) unconjugated o-synephrine (10%), (v) an acid-hydrolysable conjugate of o-synephrine (8.5%) and (vi) unconjugated o-octopamine (0.3%). Adult rats normally excreted OHMA (1.0 micrograms day-1) but OHPG, o-octopamine and o-synephrine could not be detected in urine. After the administration of a monoamine oxidase inhibitor, unconjugated o-octopamine (0.3 micrograms day-1) was excreted in urine but OHPG and o-synephrine could not be detected. o-Tyramine given to rats afforded urinary o-octopamine (75 ng day-1) and this was increased 10-fold upon co-administration of a monoamine oxidase inhibitor and o-tyramine.

Animals↗
PubMed1996

Antidepressant-like effects of p-synephrine in mouse models of immobility tests.

We studied the effects of p-synephrine on the immobility behaviors and on the spontaneous motor activity in mice. p-Synephrine at oral doses from 1 to 10 mg/kg significantly decreased the duration of immobility in the tail suspension test and the forced swimming test in mice. At 30 mg/kg, the duration of immobility was returned to control values in both tests. Subcutaneous administration of prazosin hydrochloride (62.5 micrograms/kg), an alpha 1 adrenoceptor antagonist, blocked the p-synephrine (3 mg/kg)-induced decrease in immobility in the tail suspension test. p-Synephrine did not change the spontaneous motor activity at oral doses from 0.3 to 10 mg/kg. These results suggest that p-synephrine elicits an antidepressant-like activity in mouse models of immobility tests, through the stimulation of alpha 1 adrenoceptors.

Adrenergic alpha-1 Receptor Antagonists↗
PubMed1984

Effect of intracerebroventricularly administered octopamines and synephrines on angiotensin II-induced water intake in rats.

Recent studies from this laboratory showed that l-m-synephrine (phenylephrine), a metabolite of l-m-octapamine, inhibited the drinking response of rats to peripherally administered angiotensin II. The objective of this investigation was to determine whether the isomers of both octapamine and synephrine could inhibit angiotensin II-induced dipsogenesis in the rat. Of the isomers tested, only d,l-m-octopamine and l-m-synephrine blocked the dipsogenic response to administration of angiotensin II (200 micrograms/kg, SC). The antidipsogenic effect of both d,l-m-octopamine and l-m-synephrine could be blocked by concurrent administration of yohimbine (300 micrograms/kg, IP), an alpha 2-adrenoceptor antagonist. The results indicate that m-octopamine and m-synephrine exert their antidipsogenic effect via alpha 2-adrenoceptors. These studies add to a growing body of data suggesting that activation of alpha 2-adrenoceptors inhibits, while blockade of these receptors enhances, angiotensin II-induced drinking.

2-Hydroxyphenethylamine↗
PubMed1987

Beta-adrenergic activities of octopamine and synephrine stereoisomers on guinea-pig atria and trachea.

The activities of the (-)- and (+)-forms of m- and p-octopamine and m- and p-synephrine on beta 1- and beta 2-adrenoceptors in guinea-pig atria and trachea have been compared with that of noradrenaline. The rank order of potency of the (-)-forms on beta 1-adrenoceptors was noradrenaline greater than m-synephrine greater than m-octopamine = p-octopamine greater than p-synephrine. m-Synephrine was 100-fold, m- and p-octopamine about 6000-fold, and p-synephrine about 40,000-fold less active than noradrenaline. The (+)-forms were 1-2 orders of magnitude less active than their (-)-counterparts. The four (-)-compounds were more than four orders of magnitude less active than noradrenaline on beta 2-adrenoceptors, and the (+)-forms had no detectable activity in concentrations as high as 10(-4) M. If m- and p-octopamine are co-released with noradrenaline in amounts proportional to their concentration, their activities at these structures are too low to be physiologically significant.

Adrenergic beta-Agonists↗
PubMedDate not supplied

Chemiluminescence of synephrine based on the cerium(IV)-rhodamine B system.

A new chemiluminescence (CL) method is described for the determination of synephrine. It is based on the reaction between synephrine and Ce(IV) in a nitric acid medium and measurement of the CL intensity produced by rhodamine B used as a luminophore, similar to luminol or lucigenin in basic media, instead of as a sensitizer. In the optimum conditions, the increase of CL intensity was correlated with synephrine concentration over the range 5.0 x 10(-9)-1.0 x 10(-6) g/mL with a detection limit of 1.0 x 10(-9) g/mL. The relative standard deviation (RSD) was 2.9% for 1.0 x 10(-7) g/mL synephrine (n = 11). The method was applied to the determination of a drug in herbal products, citrus fruit and biological samples, with satisfactory results. The results given by the proposed method are in good agreement with those given by HPLC-UV and UV spectrophotometry.

Cerium↗
PubMed2006

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

A simple and rapid procedure based on gas chromatography-mass spectrometry (GC-MS) is described for determination of synephrine, active principle of Citrus aurantium plant, in solid and liquid dietary supplements. After the addition of 3,4-methylenedioxypropylamphetamine as internal standard (I.S.), a liquid-liquid extraction procedure in alkaline conditions with chloroform/isopropanol (9:1, v/v) was applied to the samples prior to analysis. Chromatography was performed on a fused capillary column and synephrine and I.S., derivatized with pentafluoropropionic anhydride, were determined in the selected-ion-monitoring (SIM) mode. The method was validated in the range 0.1-50 microg/mg or microg/mL synephrine. Mean recovery ranged between 89.3% and 90.5% in both solid and liquid dietary supplements. The quantification limit was 0.1 microg/mg or microg/ml. The method was applied to analysis of various dietary supplements promoted for aiding weight control containing, among other constituents such as ephedrine alkaloids and methylxanthines, Citrus aurantium. Amount of synephrine present in such products ranged from 3.1 microg/mg solid product to 480.2 microg/mL liquid product.

Citrus↗