Pharmacokinetics of cathinone,cathine and norephedrine after the chewing of khat leaves

AIM: The stimulating herbal drug khat is habitually used in East Africa and the Arabian peninsula but is also imported into other countries. The aim was to study the pharmacokinetics of its alkaloids cathinone, cathine and norephedrine. METHODS: Four volunteers chewed khat leaves in an amount equivalent to one-quarter of that used in a typical khat session. Blood samples were collected up to 80 h and the alkaloids were assayed using gas chromatography-mass spectrometry. The data were evaluated using computerized pharmacokinetic compartmental analysis. RESULTS: The plasma concentration-time data for the alkaloids could be described using a two-compartment model with two-segment absorption. The mucosa of the oral cavity is considered to be the first absorption segment, where the major proportion of the alkaloids is absorbed (mean +/- SD 59 +/- 21% for cathinone and 84 +/- 6% for cathine). The extraction of the alkaloids from the leaves by chewing was very effective with only 9.1 +/- 4.2% remaining as a residue. Cathinone was eliminated from the central compartment with a mean half-life of 1.5 +/- 0.8 h. The half-life of cathine was 5.2 +/- 3.4 h. The metabolism of cathinone to norephedrine had a substantial influence on its plasma concentration profile. Psychophysical functions were essentially unaffected by the chewing of khat. CONCLUSIONS: The pharmacokinetics of khat alkaloids in humans explain why chewing is the preferred form of khat ingestion. Subjects absorbed a mean dose of 45 mg of cathinone, and did not suffer any severe adverse reactions.     

HPLC-UV法同时测定麻黄中5种麻黄生物碱的含量

目的建立同时分离检测麻黄中麻黄碱(Ephedrine)、伪麻黄碱(Pseudoephedrine)、去甲麻黄碱(Norephedrine)、去甲伪麻黄碱(Norpseudoephedrine)和甲基麻黄碱(Methylephedrine)的含量测定方法。方法采用HPLC-UV法,色谱柱:苯基柱(Alltima Phenyl,250mm×4.6 mm,5μm);流动相:0.02 mol/L磷酸二氢钾溶液-乙腈(96∶4);流速:0.6 ml/min;检测波长:210 nm;柱温:25℃。结果 5种生物碱在13.5 min内即可达到完全分离,E在2.000 8～40.016 0μg/ml线性关系良好;PE在1.003 6～20.072 0μg/ml线性关系良好;NME在0.199 2～3.984 0μg/ml线性关系良好;NMP在0.200 0～4.00 0μg/ml线性关系良好;ME在0.200 4～4.008 0μg/ml线性关系良好。各生物碱的平均回收率均在92%～104%(RSD≤5.76%)。结论本方法可操作性强,简便快速,分离效果好,重现性好,可为麻黄及含麻黄的中西药制剂提供有效的检测手段。     

基于UPLC-DAD-TOF/MS结合HPLC-UV法的麻黄“先煎去沫”样品的化学成分分析

目的建立基于UPLC-DAD-TOF/MS结合HPLC-UV法检测麻黄样品化学成分的方法,以明确麻黄"先煎去沫"样品化学成分间的差异。方法 UPLC-DAD-TOF/MS:Waters ACQUITY UPLC?BEH C18(50 mm×2.1 mm,1.7μm)色谱柱,以甲醇-0.1%甲酸水溶液为流动相梯度洗脱,体积流量0.3 m L/min,柱温40℃,正、负离子模式扫描;HPLC-UV:以十八烷基硅烷键合硅胶为填充剂(150 mm×4.6 mm,5μm),以0.1%磷酸水溶液(含0.05%三乙胺)-乙腈溶液(99∶1)为流动相,等度洗脱,体积流量1 m L/min,检测波长为210 nm,柱温30℃。结果上沫中所含成分较少,去沫下液和全煎煮液中化学成分基本一致。同时,三者均可鉴定出去甲基麻黄碱、去甲基伪麻黄碱、麻黄碱、伪麻黄碱和甲基麻黄碱5个生物碱类成分和1个羧酸类成分(4-羟基-7-甲氧基-2-喹啉羧酸)。但上沫中生物碱含量极低,而全煎煮液中3种生物碱的含量略高于去沫下液。结论麻黄"先煎去"沫理论可能与生物碱类成分关系不大,但仍需后期进行更深入的研究验证。     

Vasorelaxant effects of 2‐nitro‐1‐phenyl‐1‐propanol in rat aorta

2‐Nitro‐1‐phenyl‐1‐propanol (NPP) is a nitro alcohol that is known as an intermediate in the synthesis of sympathomimetic agents, such as norephedrine. The present study investigated the vasoactive effects of NPP on rat aorta. In endothelium‐intact aortic rings, NPP fully relaxed contractions that were induced by phenylephrine, KCl, and U‐46619. The relaxant effects of NPP on phenylephrine‐elicited contractions remained unaffected by NG‐nitro‐l ‐arginine methyl ester (l ‐NAME), indomethacin, propranolol, tetraethylammonium, 4‐aminopyridine, and glibenclamide. Conversely, pretreatment with 1H‐[1,2,4]oxadiazolo[4,3‐a]quinoxalin‐1‐one (ODQ), cis‐N‐(2‐phenylcyclopentyl)‐azacyclotridec‐1‐en‐2‐amine hydrochloride (MDL‐12,330A), and N‐[2‐(P‐bromocinnamylamino)ethyl]‐5‐isoquinolinesulfonamide dihydrochloride (H‐89) reduced the ability of NPP to relax contractions that were elicited by phenylephrine. NPP inhibited the vasoconstrictor response that was induced by Ca²⁺ in aortic rings that were stimulated by pharmacomechanical or electromechanical coupling with phenylephrine and 60 mmol/L KCl, respectively, and after the depletion of intracellular Ca²⁺ stores. Such effects of NPP were significantly reversed by pretreatment with the guanylyl cyclase inhibitor ODQ and weakly influenced by the adenylyl cyclase inhibitor MDL‐12,330A. In Ca²⁺‐free medium, NPP inhibited transient contractions that were induced by phenylephrine but not caffeine. In homogenates of aortic rings, NPP increased cyclic guanosine 3′,5′‐monophosphate (cGMP) and cyclic adenosine 3′‐5′‐monophosphate levels, but this effect was statistically significant only for cGMP. In conclusion, in contrast to the vasoconstrictor amine norephedrine, NPP is a vasodilator in rat aorta, and its relaxant effects are likely attributable to cGMP production.     

Antibacterial activities of 4-substituted-2-[(E)-{(1S,2R)/(1R,2S)-1-hydroxy-1-phenylpropan-2-ylimino}methyl]phenol

A series of norephedrine‐based Schiff bases (1a–6a and 1b–6b) were synthesized by reacting substituted salicylaldehydes with d‐norephedrine or l‐norephedrine. The structure of these compounds was confirmed by elemental analyses and spectroscopic techniques. The molecular structures of 5a and 6a have been determined by X‐ray crystallography, which revealed that the compounds are in the oxoamino form, with bent intramolecular N‐H···O (N···O ≈ 2.58 Å) hydrogen bonds and that they are associated in dimers bridged by linear intermolecular O‐H···O (O···O ≈ 2.69 Å) hydrogen bonds. The density functional theory calculations on 5a confirmed that the oxoamino form is more stable than the phenolimino form by 12.2 kcal/mol. All the compounds were evaluated for their antibacterial activity using resazurin dye as indicator by twofold dilution method against four bacteria namely, Bacillus subtilis (NCIM2718), Staphylococcus aureus (NCIM5021), Escherichia coli (NCIM2931), and Proteus vulgaris (NCIM2813).     

Influence of Skin Irritants on Percutaneous Absorption

The effects of the application of skin irritants on the in vitro percutaneous absorption of three model compounds of diverse physico-chemical properties, caffeine, indomethacin, and hydrocortisone, were investigated. Norephedrine and imipramine, basic drugs with a known skin irritation potential, were employed to damage the skin. Treatment with norephedrine increased the permeation of caffeine and hydrocortisone by two- to fourfold, while absorption of indomethacin declined an order of magnitude. A similar result was obtained for the effect of treatment with imipramine on transport of caffeine. Pretreatment with imipramine promoted hydrocortisone absorption 10-fold but, unlike norephedrine, did not alter indomethacin permeation. While both treatments in vivo caused an increase (norephedrine > imipramine) in the pH on the surface of skin and after tape-stripping the skin, only norephedrine caused changes in transepidermal water loss in vivo in man. Since imipramine was the more severe irritant as judged by erythema, alterations by irritants of barrier function appeared rather complex.     

Excretion of norephedrine by man after oral administration of oxyfedrine

Summary After oral administration of oxyfedrine to healthy volunteers, norephedrine was identified in the urine by thin layer chromatography and gas liquid chromatography and mass spectrography. 30 hours after single oral doses of 8, 16 or 24 mg of oxyfedrine, about 4, 8 and 9 mg, respectively, of norephedrine were found in the urine, i.e. on a molar base 75–100% of the dose was excreted as norephedrine. The peak of excretion occurred within 2–4 hours after administration of the drug. No accumulation of oxyfedrine and/or its metabolite was observed after administration of 16 mg of oxyfedrine t.i.d. for three days. It could not be decided whether oxyfedrine was metabolized to norephedrine by liver enzymes, as in rats, or was spontaneously degraded to norephedrine, e.g. in duodenal fluid before absorption. 30–150 min after oral oxyfedrine (24 mg) norephedrine was demonstrable in duodenal fluid. Thus, in addition to the direct-sympathomimetic effects of oxyfedrine, it may also have indirect sympathomimetic effects because of the noradrenaline-releasing properties of its metabolite norephedrine.Presented in part at the 79. Tag.Dtsch.Ges.Inn.Med., Wiesbaden, 1973 (Appelet al., 1973^b). The work was supported by grants from the Deutsche Forschungsgemeinschaft