A suite of three dietary supplement standard reference materials (SRMs) containing bitter orange has been developed, and the levels of five alkaloids and caffeine have been measured by multiple analytical methods. Synephrine, octopamine, tyramine, N-methyltyramine, hordenine, total alkaloids, and caffeine were determined by as many as six analytical methods, with measurements performed at the National Institute of Standards and Technology and at two collaborating laboratories. The methods offer substantial independence, with two types of extractions, two separation methods, and four detection methods. Excellent agreement was obtained among the measurements, with data reproducibility for most methods and analytes better than 5% relative standard deviation. The bitter-orange-containing dietary supplement SRMs are intended primarily for use as measurement controls and for use in the development and validation of analytical methods.
Reversed-phase high-performance liquid chromatography utilizing photodiode array detection is used for the simultaneous determination of caffeine and nine alkaloids from Citrus aurantium (CA) and ephedra (EA) contained in dietary weight loss products. Since the Food and Drug Administration (FDA) ban of EA, manufacturers have substituted CA in their weight loss formulations, usually combined with high levels of caffeine. The alkaloids contained in CA have some physiological effects similar to those of the EA alkaloids and are, therefore, cause for concern. Caffeine has been shown to potentiate the toxicity of the EA alkaloids. Recently, a federal judge overturned the absolute ban and allowed marketing of low levels (<10 mg/day) of total EA alkaloids. To support an absolute ban, the FDA is now compelled to perform dose-dependent toxicology studies to determine the toxic dose(s) of EA. The toxicity of the CA compounds is largely unknown, especially in combination with caffeine. The described method enables quantitation over a wide range of product formulations. Recoveries range from 91% to 100% from a variety of fortified plant matrices.
In common with halogenated anaesthetics, nicorandil, a new KATP channel opener, has been shown to have cardioprotective and vasodilator effects. Recent studies have also suggested that the vasodilator and protective effects of halogenated anaesthetics are mediated partly via KATP channel opening. This study examined the effects of concurrent administration of nicorandil and isoflurane on haemodynamic state and ventricular function before, during and after 15 min of ischaemia. We studied left ventricular function in 40 anaesthetized rabbits using ultrasonomicrometry. Measurements were obtained before, during and after 15 min of regional ischaemia. Regional ventricular function was assessed in terms of systolic shortening (SS%) and preload recruitable work area (PRWA, the area beneath the regional stroke work vs end-diastolic length relationship) during reperfusion. Four groups were studied: group F (n = 10) received a bolus dose of fentanyl 100 micrograms kg-1 and then 400 micrograms kg-1 h-1 throughout; group 1 (n = 10) received 2.05% end-tidal concentration of isoflurane (1 MAC); group FN (n = 10) received fentanyl, a bolus does of nicorandil 100 micrograms kg-1 and then 25 micrograms kg-1 min-1, 15 min before occlusion; and group IN (n = 10) received isoflurane and nicorandil. Isoflurane decreased left ventricular systolic pressure and ventricular contractility (+dP/dtmax, slope of preload recruitable stroke work, and SS%). Nicorandil increased -dP/dtmax in group FN. Post-ischaemic regional left ventricular contractility in group I did not differ from that in group F, however, groups receiving nicorandil recovered to a greater extent. Group IN showed better recovery compared with all other groups when ventricular contractility was assessed by PRWA normalized to pre-occlusion values (mean 99.3 (SEM 10.5)% vs 73.4 (7.5)%, 50.2 (5.8)% and 52.4 (3.7)% at 120 min reperfusion in groups FN, I and F, respectively). Tissue ATP and lactate contents did not differ between groups. We conclude that concurrent administration of nicorandil and isoflurane enhanced post-ischaemic recovery compared with isoflurane anaesthesia or nicorandil and fentanyl administration.
Ethinyl estradiol (EE2) is an extremely potent synthetic estrogen and a common component in oral contraceptives. The drug has a well-characterized pharmacological profile and is used as a positive control in toxicological investigations of compounds having estrogenic activity. An analytical method developed for the determination of low microg/kg levels of EE2 in a casein-based rodent diet is presented. A methanol extract of casein diet is purified for instrumental analysis by a 3-fold solid-phase extraction process. The sample extract is derivatized with pentafluoropropionic anhydride to the pentafluoropropionyl product and analyzed by capillary gas chromatography with electron-capture detection. Recoveries of EE2 from casein diet fortified at 5, 10, and 50 microg/kg average 88.8% and have a relative standard deviation (%) of 7.2. The method limit of detection in a casein-based diet is 1 microg/kg.
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