The chewing of khat, which typically consists of the young leaves and stems of the Catha edulis plant, for its stimulant effects has in the past been largely confined to its area of cultivation, namely, East Africa and the Arab Peninsula. Historically, cathine [(+)-norpseudoephedrine] (Fig. 1), was erroneously identified to be the active compound in khat which was responsible for the observed pharmacological effects because the investigations were based on dried or old plant samples. However, discrepancies in drug potency signaled to researchers that another compound was accountable for the effects. Using fresh young leaves or otherwise well-preserved khat samples, cathinone (2-amino-1-phenyl-1-propanone) (Fig. 2), was finally isolated and identified as the principal alkaloid^1-8. Cathinone is estimated to be one-third as potent as amphetamine and ten times more potent than cathine⁹, and it has been found that during the maturation of the leaves or decomposition of the plant through drying and storage, cathinone contained within the plant is enzymatically converted to cathine⁵.

Fig. 1-2
Cathine (left) and Cathinone (right)

Effective February 1993, cathinone was placed into Schedule I of the Controlled Substances Act¹⁰. Khat is a Schedule I substance when cathinone is present. Cathine is ruled as a Schedule IV substance¹¹. When the plant no longer contains detectable levels of cathinone, as in older leaf samples, but contains cathine khat is classified as a Schedule IV substance. This causes a logical problem with cathinone detection since fresh khat leaves (or an otherwise well-preserved sample) are needed for the analysis, an order for the sentence of a Schedule I drug to be invoked.

Fresh leaves are traditionally chewed as the cut khat loses its potency about 3 to 4 days after harvesting². Despite the short period of drug effectiveness, the availability of rapid air freight service has resulted in the appearance of khat in non-origin countries, for example, United States, Italy, and Great Britain. Although it is now recognized that the rapid extraction and analysis of fresh khat samples is needed, the time frame required for cathinone detection has not yet been adequately addressed. Further, the fo[...] of past khat studies relied upon using freshly picked khat samples, deep-freeze and freeze-dried preservation techniques, and temporary dry ice storage so that cathinone detection would be inst[...]^2,7,9,12,13. For law enforcement purposes, such specialized preservation techniques are not generally feasible or readily available at seizure sites. More practical means of sample storage and preservation were investigated in this study so that reasonable guidelines and expectations for cathinone detection in seized khat drug evidence could be made available. In addition to this, the use of vapor phase infrared detection (IRD) and mass spectrometry (MS) were evaluated for their specificity in cathinone and cathine identification.

Results

Dried Samples Stored at Room Temperature

[...] Day 1 as the day the khat material was harvested, 5 g leaves and stems were removed from the paper bag on a daily [...] and analyzed. Cathinone was detected as the major component [...] the Day 2 run of the IRD total response chromatogram [...] through Day 7 (Fig. 3). None or only a trace amount of [...] was detectable. On Day 5, cathine became detectable, in [...] to cathinone. By Day 11, the cathinone IRD peak height [...] TRC was twice or equivalent to the cathine peak, which made a positive identification for cathinone difficult, but still possible, due to the poor chromatographic separation. As the plant dried, more leaves were needed to yield the 5 g sample size. Analyses [...] longer time periods were not performed since there was insufficient [...] air-dried sample. The IRD detection of cathinone after 10 days of air drying is consistent with an earlier work which used thin layer chromatography (TLC) to verify the presence of cathi[...] collected khat samples that were first stored in thermoflasks containing dry ice for 3-4 days, then later allowed to air dry for 7 to 10 days¹².

The IRD spectra for cathinone and cathine isolated from the Catha edulis cuttings are shown in Figs. 4a,b and the mass spectra for cathinone and cathine standards are provided in Figs. 5a,b. Previous works have described using high-pressure liquid chromatography, gas chromatography, infrared spectroscopy, MS and TLC to identify cathinone and cathine. The mass spectra for the cathinone and cathine standards (Fig. 5a,b) are very similar, with an identical base peak at m/e 44 for both compounds. Some groups have used acetylation to better identify the two components by MS⁸. However, the IRD spectra for cathinone and cathine are unambiguous and unique (Fig. 4a,b).

Refrigerated Samples

A 3.5 g khat sample that was stored in a refrigerator for two weeks, exhibited cathinone and cathine (Fig. 6).

Frozen Samples

Samples stored in the freezer for 34 days and 48 days before showed cathinone and cathine, with the cathine levels in high concentration in the latter sample (Figs. 7a,b).

Actual Khat Exhibit

While this study was in progress, an actual khat exhibit was submitted to the Western Laboratory within four days of a U.S. Customs import seizure. Although the sample was sent by overnight delivery and analyzed on the day of receipt, the exhibit had undergone significant spoilage as evidenced by a foul smell and a disproportionately large amount of wet, brown leaves. There have been a number of [...] seizures submitted to several DEA field laboratories where the plant shoots were bundled and wrapped in large plant leaves. In this particular case, the submitted plant exhibit was packaged in plastic bags rather than in leaves which severely restricted air flow around the plant cuttings. Although approx. 50% of the leaves still appeared to be in a fresh condition and were selectively used for the analysis, cathinone was fairly difficult to detect since its IRD peak height was only one-third that for cathine.

Recommendations for submitting khat samples to the laboratory include:

1. Sending a representative sampling of the exhibit in [...] paper bags
2. Packing the bags in sturdy cardboard boxes (which should then be properly sealed)
3. Providing advance notice of the khat shipment to the laboratory
4. Sending the shipment by overnight delivery
5. Storing the plant cuttings in a cool area until the analysis is conducted

[...] Findings

Work by the DEA Northeast Laboratory has found that cathinone concentrated in the leaves rather than in the stems which is consistent with previous studies^12,13. This present work supports earlier findings^2,5,9 that once the plant cuttings are harvested, the cathinone concentration within the plant gradually decreases with the concomitant formation of cathine. However, once cathinone is extracted from the khat leaves, the reduction process from cathinone to cathine ceases to occur.

Fig. 8
3,6-Dimethyl-2,5-Diphenylpyrazine

An undesired side reaction which develops during the cathinone isolation step is the oxidative dimerization of cathinone (3,6-dimethyl-2,5-diphenylpyrazine)^2,7,8, and which significantly decreases the amount of cathinone detected. [...] rapid workup and analysis are recommended once the extraction process is completed to facilitate the detection of cathinone⁸. Although the results presented in this study are based on several khat plants, it should be noted that cathinone levels in the plant can be highly variable; depending on factors such as species, plant maturity, [...] and quality⁹.

Conclusions

This study provides conclusive results that cathinone can be extracted from harvested khat (Catha edulis) despite the elapse of almost two weeks to a month, when the plant samples do not visibly appear to be in their original freshly cut condition. Through proper sample handling, the sample holding time for khat plant material may be significantly extended while at the same time, allow for legal due process of a Schedule I drug, cathinone, rather than the Schedule IV drug, cathine.

The use of vapor phase infrared spectroscopy to identify cathinone and cathinone provides unambiguous and unequivocable spectra relative to that obtained by mass spectrometry.

• Fig. 1: Cathine
• Fig. 2: Cathinone
• Fig. 3: IRD total response chromatogram for plant extract
• Fig. 4a: IRD spectrum of cathinone from khat
• Fig. 4b: IRD spectrum of cathine from khat
• Fig. 5a-b: Mass spectrum of cathinone and cathine standard
• Fig. 6: IRD total response chromatogram of khat (refrigerated 2 weeks)
• Fig. 7a-b: IRD total response chromatogram of khat (frozen 34 and 48 days)
• Fig. 8: 3,6-dimethyl-2,5-Diphenylpyrazine
• Fig. 9: Mass spectrum of cathinone dimer