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Rapid TLC identification test for khat (Catha edulis)
Forensic
Science
International,
Elsevier Scientific Publishers
RAPID
TLC IDENTIFICATION
T. LEHMANN, Institute
45 (1990) 47-51
S. GEISSHOSLER
of Phamacy,
47
Ireland Ltd.
University
TEST
FOR KHAT
(CATHA
EDULIS’J
and R. BRENNEISEN* of Berne
Kwitzerlund)
(Received April 12th, 1989) (Revision received August 3rd. 19891 (Accepted August 7th, 19891
Summary A rapid and sensitive method for identification of Catha edulis (khat) basing on a simple extraction and TLC separation is described. The test is specific for the main khatamines cathinone and norpseudoephedrine. Key words: Khat (Catha edulis); Cathinone; Identification
Norpseudoephedrine;
Thin layer chromatography;
Introduction
Khat, the leaves or short tops of the evergreen plant Cutha edulis Forsk. (Celastraceael, is well known in East Africa (Kenya, Ethiopia, Madagascar) and the Arabian peninsula (North Yemen) for being chewed habitually by many people. At present, khat has begun to be introduced to certain developed countries, e.g. Great Britain, were use of khat among East African and Yemeni immigrants is substantial [l]. Shipments of khat - mostly by air transportation - have been observed too by customs authorities in France and the United States [1,2]. The widespread use and popularity is due to its CNS-stimulating phenylpropylamines, especially to cathinone (a-aminopropiophenone, ‘natural amphetamine’) and to a much lesser extent to norpseudoephedrine (‘cathine’l and norephedrine [l-6]. After the World Health Organisation recommended that cathionine be placed under international control, the amphetamine-like substance has been included in Schedule I of the UN Convention on Psychotropic Substances. The recently found phenylpentenylamines merucathinone, merucathine and pseudomerucathine [3,7 - 91 play only a minor role concerning the psychoactive effects of khat [lo]. In the guidelines for future investigations which were formulated by the UN Expert Group on the Botany and Chemistry of Khat in 1979 [ll], an ‘urgent need for specific qualitative means of identification of khat material and quantitative analysis of the important plant constituents’ was emphasized. Whereas a HPLC method for the quantitation of all known khatamines 0379-0738/90/$03.50
0 1990 Elsevier Scientific Publishers Printed and Published in Ireland
Ireland Ltd.
has already been proposed [3,12,13], to our knowledge no simple and reliable test for identification of khat samples has been published until now. The method of Rijhm and Schmid [14] is based on a very time consuming extraction (6-15 hl and is therefore not suited for a rapid identification. Furthermore the proposed thin layer chromatography (TLC) system results in inefficient separation of complex khat extracts (e.g. MeOH extracts). A macroscopic, microscopic and histochemical examination of khat leaves does not show enough characteristics and is inappropriate for forensic purposes. Nordal and Laane [15] suggested a combination of morphological, histochemical and chromatographic (TLC and GC) methods. Therefore, our aim was to establish a specific and sensitive test for khat based on a rapid, simple and inexpensive TLC method. With minimum laboratory equipment it can be used for forensic and law enforcement applications. The proposed TLC method was developed and tested by repeated analysis of numerous Catha samples of different type, origin and age which have been screened before for khatamines by HPLC and GC profiling [8,12,13,19]. Material and Methods
Most of the khat samples (Catha edulis) were bought between 1982 and 1986 at the khat markets of Addis Ababa and Awedai/Harrar (Ethiopia), Nairobi and Mombasa (Kenya), Sanaa (North Yemen) and Anivorano (Madagascar). The specimens were deep-frozen within 24 h, transported by air in a cooler to the laboratory and stored at - 20°C until used. Dried khat samples originating from South Africa and Catha transvaalensis were obtained through the Lowveld Botanic Garden, Transvaal and the Johannesburg Botanic Garden, Johannesburg (South Africa). Catha spinosa and Ephedra dystachia were cultivated at the Botanical Garden of the University of Berne. Duplicates of all analyzed specimens are being kept in the herbarium of the Institute of Pharmacy, University of Berne. One leaf (medium size, corresponding to about 500 mg fresh or 150 mg dried plant material1 of a khat sample and 2.5 ml MeOH were ground thoroughly in a mortar. The suspension was then transferred to a 2.5-ml vial with cap and sonicated for 10 min. After passing through a 0.2~pm cellulose filter (or through the tip of a Pasteur pipette filled with cotton wool) the clear and greenish solution was concentrated to about 100 ~1 under a stream of nitrogen and again filtered. If no ultrasonic bath is available the following alternative extraction procedure is recommended: one leaf of a khat sample and 5 ml MeOH were ground properly in a mortar. The suspension was then transferred to a test tube with stopper and shaken vigorously for 10 min. After filtration through a 5-cm paper filter the solution was concentrated to about 250 ~1 on a water bath (70°C) and again filtered through the tip of a Pasteur pipette filled with cotton wool. Five microlitres of the filtrate were applied bandwise (5-mm line) to a TLC plate (Macherey-Nagel Alugram Sil G/UV,,, 0.25 mm, 40 x 80 mm or an
49
equivalent product) and developed in EtOAc-MeOH-NH, 25% 85 : 10 : 5 [15,16]. A methanolic solution of about 1 mglml of cathinone hydrochloride (synthesized according to [6]) and norpseudoephedrine or norephedrine hydrochloride (Sigma Chemical Comp., St. Louis, U.S.A.) was used as standard. Prior to visualization the plate must be dried at room temperature or, more quickly, by short use of a hot air blower. The plate was observed under visible and UV light (254 nm), sprayed with fresh ninhydrin reagent (0.3 g in 100 ml n-butanol + 3 ml cone. acetic acid) and heated at llO°C for 2 min. Results and Discussion
An extraction without partition and with MeOH only as solvent was chosen to get complex TLC patterns showing the khat sample zones of the typical khatamines and other constituents (Figs. la-c). Under visible light (Fig.
m 0.0
mm0
_-
53D(tiD~ -
3
2
3
4
5
6
7
8
9
10
1
2
3
4
5
6
7
8
9
10
Rr
Fig. 1. Thin-layer chromatograms of Cutha edulis (khatl and the main khatamines in comparison with other Cutha species and Ephedra (al VIS detection; (bl UV,,, detection; (cl Ninhydrin detection. (11 Catha edulis “Kenya”; (21 Catha edulis “Ethiopia”: (31 Catha edulis “North Yemen”; (4) Catha edulis “South Africa”; (51 Catha edulis “Madagascar”; (61 Catha transvaalensis; (71 Catha spinosa; 631 Ephedra dystachia; (91 Cathinone ( = Cl; (101 Norephedrine/norpseudoephedrine (= Nl. ? ?, green; ? ?, yellow; I , light-yellow; H , reddish; H , grey-yellow; I , grey-green; violet; I , brown-green; ? ?, white: ? ?, grey; ? ?, dark-blue.
50
la1 khat samples show a brown-green zone of polar products (flavonoids) on the starting line and at R, 0.06 a grey zone, at Rf 0.62 a light-yellow and at 0.72 a yellow zone, probably artifacts (decomposition products of the unstable cathinonel can be observed. At Rf 0.82 a green zone locates the colouring principle of the plant (chlorophyll). Under UV,,, cathinone is visualized as a dark-blue zone at Rf 0.43 (Fig. lb) and in higher concentrations shows a violet zone after spraying with ninhydrin reagent (Fig. 1~1. Norpseudoephedrine and norephedrine are not or only weakly visible under UVZs4, due to a hundred times lower E-value than cathinone, but can be visualized with ninhydrin as pink zone at R, 0.25-0.3 (not separated). The minimum detectable amount of cathinone and norpseudoephedrine is about 250 ng (VU,,,) and 3 pg (ninhydrinl, respectively. If 5 ~1 of the filtered extracts are used for TLC, this corresponds to a relative detection limit of 0.5 pg cathinone and 6 pg norpseudoephedrinelnorephedrine/lOO mg dried khat leaves. The sensitivity of the test is therefore sufficient to identify even one leaf of a khat sample with low phenylalkylamine content, e.g. khat from Yemen and Madagascar [13]. The phenylpentenylamines can not be separated from the corresponding phenylpropylamines and are always below the detection limit. As cathinone has only been found in Catha edulis a positive identification of this compound is a specific indication for khat. Nevertheless, positive results should be confirmed by an alternative technique, such as high-performance liquid chromatography (HPLC), gas chromatography (GC) or gas chromatography/mass spectrometry (GC/MS) [3,8,12,13,16]. Catha spinosa (endemic in North Yemen [17]1 and Catha transvaalensis (endemic in South Africa [18]) have a morphology similar to Catha edulis but produce different TLC patterns (Figs. la-cl. A phytochemical study of these relatively unknown Catha species is in progress [19]. The total content of khatamines and especially the concentration ratios of cathinone, norpseudoephedrine and norephedrine are dependent on the khat type, origin, time of harvesting, drying method, age and storage conditions [3,6,8,12,13]. Dried and old khat samples usually contain only very small but still TLC detectable amounts of cathinone due to enzymatic reduction of cathinone to norpseudoephedrine and norephedrine [3,6,12]. In such plant material norpseudoephedrine is the dominating khatamine [12,13]. But in any case only a quantitative analysis of major and minor khatamines, for example by HPLC profiling [12,13], provides more information about the “history” and the psychotropic potency of a given khat sample. Other plants with as Ephedra species, are such norpseudoephedrine as constituent, morphologically different from khat and give not the same pattern (Figs. la- lcl. Rapid but unspecific colour tests (Marquis’, modified Marquis’, Froehde’s, Simon’s, Chen-Kao’s or Mandelin’s reagent [20-22311 for the presumptive identification of phenylalkylamines do not give positive results with cathinone and norpseudoephedrine. Therefore the commercially available
51
Merck colour test for amphetamine (part of the Drug Identification Kit no. 11850) or the UN colour test for amphetamines (part of the UN Drug Identification Kit), both use the modified Marquis’ reagent, are not suitable for testing khat samples. References 1
P. Kalix, Khat: a plant with amphetamine
effects. J. Subst. Abuse
Treatm.,
5 (1988) 163-
169.
2 3 4
8 9 10
P. Kalix and 0. Braenden, Pharmacological aspects of the chewing of khat leaves. PharmacoL Rev., 37 (1985) 149- 164. R. Brenneisen and S. Geisshiisler, Psychotropic Drugs III: Analytical and chemical aspects of Catha edulis Forsk. Phunn. Acta Helv., 60 (1985) 290-301. United Nations Narcotics Laboratory, Studies on the chemical composition of Khat III: Investigations on the phenylalkylamine fraction. UN Docum. MNAR, 11, 1975. X. Schorno and E. Steinegger, The phenylalkylamines of Catha edulis Forsk.: The absolute configuration of cathinone. UN Docum. MNAR, 7 (1978). X. Schorno, Ph.D. Thesis, University of Berne, 1979. R. Brenneisen, S. Geisshiisler and X. Schorno, Merucathine, a new phenylalkylamine from Catha edulis. Planta Med., 50 (1984) 531. S. Geisshiisler, Ph.D. Thesis, University of Berne, 1988. R. Brenneisen and S. Geisshtisler, Phenylpentenylamines from Catha edulis. J. Nat. Prod., 50 (1987) 1188- 1189. P. Kalix, S. Geisshtisler and R. Brenneisen, The effect of phenylpentenyl-khatamines on the release of radioactivity from rat striatal tissue prelabelled with [3H]dopamine. J. Pharm. Pharmacol,
39 (1987) 135-
137.
11
United
12
MNAR, 3, 1979. X. Schorno, R. Brenneisen
13
Helw., 57 (1982) 168- 176. S. Geisshiisler and R. Brenneisen,
14 15 16 17 18 19 20 21 22 23
Nations
Narcotics
Laboratory,
The botany
and chemistry
of khat.
UN Docum.
und E. Steinegger, Qualitative und quantitative Untersuchungen iiber das Vorkommen ZNS-aktiver Phenylpropylamine in Handelsdrogen und iiber deren Verteilung in verschiedenen Organen von Catha edulis Forsk. (Celastraceael Pharm. Acta
The content of psychoactive phenylpropyl and phenylpentenyl khatamines in Catha edulis Forsk. of different origin. J. Ethnopharmacol, 19 (1987) 269-277. E. Rohm und H.V. Schmid, Empfindliche Nachweismethoden fur das Stimulans Khat. Arch. Kriminol., 155 (1975) 155- 162. A. Nordal and M.M. Lane, Identification of khat. Medd Norsk. Farm. Selsk, 40 (1978) l18. K. Szendrei, The chemistry of khat. Bull. Nurcot., 32 (1980) 5-35. R. Revri, Ph.D. Thesis, University of Hohenheim, 1983. S. Demisew, Botanical aspects of “khat”, Proceedings of the International Symposium on Khat, Addis Ababa, 1984. S. Geisshtisler and R. Brenneisen, in prep. H. Auterhoff und K.-A. Kovar, Zdentifizierung von Arzneistoffen, 5. Aufl., Wiss. Veriagsgesellsch., Stuttgart, 1985. P.W. Ditzel und K.-A. Kovar, Rausch- und Suchmittel, Deutscher Apotheker Verlag, Stuttgart, 1983. United Nations, Div. of Narcotic Drugs, Recommended Methods for Testing Amphetamine and Methamphetamine, New York, 1987. United Nations, Div. of Narcotic Drugs, Rapid Testing Methods of Drugs of Abuse, New York, 1988.
Science
International,
Elsevier Scientific Publishers
RAPID
TLC IDENTIFICATION
T. LEHMANN, Institute
45 (1990) 47-51
S. GEISSHOSLER
of Phamacy,
47
Ireland Ltd.
University
TEST
FOR KHAT
(CATHA
EDULIS’J
and R. BRENNEISEN* of Berne
Kwitzerlund)
(Received April 12th, 1989) (Revision received August 3rd. 19891 (Accepted August 7th, 19891
Summary A rapid and sensitive method for identification of Catha edulis (khat) basing on a simple extraction and TLC separation is described. The test is specific for the main khatamines cathinone and norpseudoephedrine. Key words: Khat (Catha edulis); Cathinone; Identification
Norpseudoephedrine;
Thin layer chromatography;
Introduction
Khat, the leaves or short tops of the evergreen plant Cutha edulis Forsk. (Celastraceael, is well known in East Africa (Kenya, Ethiopia, Madagascar) and the Arabian peninsula (North Yemen) for being chewed habitually by many people. At present, khat has begun to be introduced to certain developed countries, e.g. Great Britain, were use of khat among East African and Yemeni immigrants is substantial [l]. Shipments of khat - mostly by air transportation - have been observed too by customs authorities in France and the United States [1,2]. The widespread use and popularity is due to its CNS-stimulating phenylpropylamines, especially to cathinone (a-aminopropiophenone, ‘natural amphetamine’) and to a much lesser extent to norpseudoephedrine (‘cathine’l and norephedrine [l-6]. After the World Health Organisation recommended that cathionine be placed under international control, the amphetamine-like substance has been included in Schedule I of the UN Convention on Psychotropic Substances. The recently found phenylpentenylamines merucathinone, merucathine and pseudomerucathine [3,7 - 91 play only a minor role concerning the psychoactive effects of khat [lo]. In the guidelines for future investigations which were formulated by the UN Expert Group on the Botany and Chemistry of Khat in 1979 [ll], an ‘urgent need for specific qualitative means of identification of khat material and quantitative analysis of the important plant constituents’ was emphasized. Whereas a HPLC method for the quantitation of all known khatamines 0379-0738/90/$03.50
0 1990 Elsevier Scientific Publishers Printed and Published in Ireland
Ireland Ltd.
has already been proposed [3,12,13], to our knowledge no simple and reliable test for identification of khat samples has been published until now. The method of Rijhm and Schmid [14] is based on a very time consuming extraction (6-15 hl and is therefore not suited for a rapid identification. Furthermore the proposed thin layer chromatography (TLC) system results in inefficient separation of complex khat extracts (e.g. MeOH extracts). A macroscopic, microscopic and histochemical examination of khat leaves does not show enough characteristics and is inappropriate for forensic purposes. Nordal and Laane [15] suggested a combination of morphological, histochemical and chromatographic (TLC and GC) methods. Therefore, our aim was to establish a specific and sensitive test for khat based on a rapid, simple and inexpensive TLC method. With minimum laboratory equipment it can be used for forensic and law enforcement applications. The proposed TLC method was developed and tested by repeated analysis of numerous Catha samples of different type, origin and age which have been screened before for khatamines by HPLC and GC profiling [8,12,13,19]. Material and Methods
Most of the khat samples (Catha edulis) were bought between 1982 and 1986 at the khat markets of Addis Ababa and Awedai/Harrar (Ethiopia), Nairobi and Mombasa (Kenya), Sanaa (North Yemen) and Anivorano (Madagascar). The specimens were deep-frozen within 24 h, transported by air in a cooler to the laboratory and stored at - 20°C until used. Dried khat samples originating from South Africa and Catha transvaalensis were obtained through the Lowveld Botanic Garden, Transvaal and the Johannesburg Botanic Garden, Johannesburg (South Africa). Catha spinosa and Ephedra dystachia were cultivated at the Botanical Garden of the University of Berne. Duplicates of all analyzed specimens are being kept in the herbarium of the Institute of Pharmacy, University of Berne. One leaf (medium size, corresponding to about 500 mg fresh or 150 mg dried plant material1 of a khat sample and 2.5 ml MeOH were ground thoroughly in a mortar. The suspension was then transferred to a 2.5-ml vial with cap and sonicated for 10 min. After passing through a 0.2~pm cellulose filter (or through the tip of a Pasteur pipette filled with cotton wool) the clear and greenish solution was concentrated to about 100 ~1 under a stream of nitrogen and again filtered. If no ultrasonic bath is available the following alternative extraction procedure is recommended: one leaf of a khat sample and 5 ml MeOH were ground properly in a mortar. The suspension was then transferred to a test tube with stopper and shaken vigorously for 10 min. After filtration through a 5-cm paper filter the solution was concentrated to about 250 ~1 on a water bath (70°C) and again filtered through the tip of a Pasteur pipette filled with cotton wool. Five microlitres of the filtrate were applied bandwise (5-mm line) to a TLC plate (Macherey-Nagel Alugram Sil G/UV,,, 0.25 mm, 40 x 80 mm or an
49
equivalent product) and developed in EtOAc-MeOH-NH, 25% 85 : 10 : 5 [15,16]. A methanolic solution of about 1 mglml of cathinone hydrochloride (synthesized according to [6]) and norpseudoephedrine or norephedrine hydrochloride (Sigma Chemical Comp., St. Louis, U.S.A.) was used as standard. Prior to visualization the plate must be dried at room temperature or, more quickly, by short use of a hot air blower. The plate was observed under visible and UV light (254 nm), sprayed with fresh ninhydrin reagent (0.3 g in 100 ml n-butanol + 3 ml cone. acetic acid) and heated at llO°C for 2 min. Results and Discussion
An extraction without partition and with MeOH only as solvent was chosen to get complex TLC patterns showing the khat sample zones of the typical khatamines and other constituents (Figs. la-c). Under visible light (Fig.
m 0.0
mm0
_-
53D(tiD~ -
3
2
3
4
5
6
7
8
9
10
1
2
3
4
5
6
7
8
9
10
Rr
Fig. 1. Thin-layer chromatograms of Cutha edulis (khatl and the main khatamines in comparison with other Cutha species and Ephedra (al VIS detection; (bl UV,,, detection; (cl Ninhydrin detection. (11 Catha edulis “Kenya”; (21 Catha edulis “Ethiopia”: (31 Catha edulis “North Yemen”; (4) Catha edulis “South Africa”; (51 Catha edulis “Madagascar”; (61 Catha transvaalensis; (71 Catha spinosa; 631 Ephedra dystachia; (91 Cathinone ( = Cl; (101 Norephedrine/norpseudoephedrine (= Nl. ? ?, green; ? ?, yellow; I , light-yellow; H , reddish; H , grey-yellow; I , grey-green; violet; I , brown-green; ? ?, white: ? ?, grey; ? ?, dark-blue.
50
la1 khat samples show a brown-green zone of polar products (flavonoids) on the starting line and at R, 0.06 a grey zone, at Rf 0.62 a light-yellow and at 0.72 a yellow zone, probably artifacts (decomposition products of the unstable cathinonel can be observed. At Rf 0.82 a green zone locates the colouring principle of the plant (chlorophyll). Under UV,,, cathinone is visualized as a dark-blue zone at Rf 0.43 (Fig. lb) and in higher concentrations shows a violet zone after spraying with ninhydrin reagent (Fig. 1~1. Norpseudoephedrine and norephedrine are not or only weakly visible under UVZs4, due to a hundred times lower E-value than cathinone, but can be visualized with ninhydrin as pink zone at R, 0.25-0.3 (not separated). The minimum detectable amount of cathinone and norpseudoephedrine is about 250 ng (VU,,,) and 3 pg (ninhydrinl, respectively. If 5 ~1 of the filtered extracts are used for TLC, this corresponds to a relative detection limit of 0.5 pg cathinone and 6 pg norpseudoephedrinelnorephedrine/lOO mg dried khat leaves. The sensitivity of the test is therefore sufficient to identify even one leaf of a khat sample with low phenylalkylamine content, e.g. khat from Yemen and Madagascar [13]. The phenylpentenylamines can not be separated from the corresponding phenylpropylamines and are always below the detection limit. As cathinone has only been found in Catha edulis a positive identification of this compound is a specific indication for khat. Nevertheless, positive results should be confirmed by an alternative technique, such as high-performance liquid chromatography (HPLC), gas chromatography (GC) or gas chromatography/mass spectrometry (GC/MS) [3,8,12,13,16]. Catha spinosa (endemic in North Yemen [17]1 and Catha transvaalensis (endemic in South Africa [18]) have a morphology similar to Catha edulis but produce different TLC patterns (Figs. la-cl. A phytochemical study of these relatively unknown Catha species is in progress [19]. The total content of khatamines and especially the concentration ratios of cathinone, norpseudoephedrine and norephedrine are dependent on the khat type, origin, time of harvesting, drying method, age and storage conditions [3,6,8,12,13]. Dried and old khat samples usually contain only very small but still TLC detectable amounts of cathinone due to enzymatic reduction of cathinone to norpseudoephedrine and norephedrine [3,6,12]. In such plant material norpseudoephedrine is the dominating khatamine [12,13]. But in any case only a quantitative analysis of major and minor khatamines, for example by HPLC profiling [12,13], provides more information about the “history” and the psychotropic potency of a given khat sample. Other plants with as Ephedra species, are such norpseudoephedrine as constituent, morphologically different from khat and give not the same pattern (Figs. la- lcl. Rapid but unspecific colour tests (Marquis’, modified Marquis’, Froehde’s, Simon’s, Chen-Kao’s or Mandelin’s reagent [20-22311 for the presumptive identification of phenylalkylamines do not give positive results with cathinone and norpseudoephedrine. Therefore the commercially available
51
Merck colour test for amphetamine (part of the Drug Identification Kit no. 11850) or the UN colour test for amphetamines (part of the UN Drug Identification Kit), both use the modified Marquis’ reagent, are not suitable for testing khat samples. References 1
P. Kalix, Khat: a plant with amphetamine
effects. J. Subst. Abuse
Treatm.,
5 (1988) 163-
169.
2 3 4
8 9 10
P. Kalix and 0. Braenden, Pharmacological aspects of the chewing of khat leaves. PharmacoL Rev., 37 (1985) 149- 164. R. Brenneisen and S. Geisshiisler, Psychotropic Drugs III: Analytical and chemical aspects of Catha edulis Forsk. Phunn. Acta Helv., 60 (1985) 290-301. United Nations Narcotics Laboratory, Studies on the chemical composition of Khat III: Investigations on the phenylalkylamine fraction. UN Docum. MNAR, 11, 1975. X. Schorno and E. Steinegger, The phenylalkylamines of Catha edulis Forsk.: The absolute configuration of cathinone. UN Docum. MNAR, 7 (1978). X. Schorno, Ph.D. Thesis, University of Berne, 1979. R. Brenneisen, S. Geisshiisler and X. Schorno, Merucathine, a new phenylalkylamine from Catha edulis. Planta Med., 50 (1984) 531. S. Geisshiisler, Ph.D. Thesis, University of Berne, 1988. R. Brenneisen and S. Geisshtisler, Phenylpentenylamines from Catha edulis. J. Nat. Prod., 50 (1987) 1188- 1189. P. Kalix, S. Geisshtisler and R. Brenneisen, The effect of phenylpentenyl-khatamines on the release of radioactivity from rat striatal tissue prelabelled with [3H]dopamine. J. Pharm. Pharmacol,
39 (1987) 135-
137.
11
United
12
MNAR, 3, 1979. X. Schorno, R. Brenneisen
13
Helw., 57 (1982) 168- 176. S. Geisshiisler and R. Brenneisen,
14 15 16 17 18 19 20 21 22 23
Nations
Narcotics
Laboratory,
The botany
and chemistry
of khat.
UN Docum.
und E. Steinegger, Qualitative und quantitative Untersuchungen iiber das Vorkommen ZNS-aktiver Phenylpropylamine in Handelsdrogen und iiber deren Verteilung in verschiedenen Organen von Catha edulis Forsk. (Celastraceael Pharm. Acta
The content of psychoactive phenylpropyl and phenylpentenyl khatamines in Catha edulis Forsk. of different origin. J. Ethnopharmacol, 19 (1987) 269-277. E. Rohm und H.V. Schmid, Empfindliche Nachweismethoden fur das Stimulans Khat. Arch. Kriminol., 155 (1975) 155- 162. A. Nordal and M.M. Lane, Identification of khat. Medd Norsk. Farm. Selsk, 40 (1978) l18. K. Szendrei, The chemistry of khat. Bull. Nurcot., 32 (1980) 5-35. R. Revri, Ph.D. Thesis, University of Hohenheim, 1983. S. Demisew, Botanical aspects of “khat”, Proceedings of the International Symposium on Khat, Addis Ababa, 1984. S. Geisshtisler and R. Brenneisen, in prep. H. Auterhoff und K.-A. Kovar, Zdentifizierung von Arzneistoffen, 5. Aufl., Wiss. Veriagsgesellsch., Stuttgart, 1985. P.W. Ditzel und K.-A. Kovar, Rausch- und Suchmittel, Deutscher Apotheker Verlag, Stuttgart, 1983. United Nations, Div. of Narcotic Drugs, Recommended Methods for Testing Amphetamine and Methamphetamine, New York, 1987. United Nations, Div. of Narcotic Drugs, Rapid Testing Methods of Drugs of Abuse, New York, 1988.