Cathinone Level Determination in Khat Leaves by Quantitative Nmr Methods
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Date
2013-11-11
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Addis Ababa University
Abstract
Catha edulis, commonly known as Khat, belongs to the family Celastraceae. Cathinone is the principal psychoactive constituent which is responsible for the stimulant effects of the leaves of the plant. In this work, rapid and simple quantitative proton NMR (qHNMR) method was developed for the first time in order to determine cathinone level. The method involves extracting chewable or dry Khat leaves with 1N oxalic acid, then basifying with 1M NaOH to pH 12 followed by EtOAc extraction. In this project, histidine and caffeine were tested as internal standards. Histidine was found to be the better choice for quantification of cathinone due to its high degree of solubility in D2O and because it has comparable molecular weight like cathinone. The method employs proton NMR spectrum of a weighed cathinone to which known amount of the internal reference, histidine, is added. The amount of cathinone present in the NMR tube is then determined by calculating the peak integration ratio of selected signal of cathinone and a signal of a proton of the reference, histidine. The amount of cathinone in the weighed fresh and dried Khat leaves originating from Wendo and Jimma were found to fall in the range of 0.02 - 0.04%. These results are in agreement with values reported before in the literature. In the course of this work, two flavonoids (KNA-1 and KNA-2) were isolated and characterized from the non-alkaloidal fractions of the plant. KNA-1 is identified as 2,3-dihydro-5,7-dihydroxy-2-(3,4,5-trihydroxyphenyl)-3-(tetrahydro-3,4,5-trihydroxy-6-methyl-2H-pyran-2-yloxy)chromen-4-one (2,3-dihydromyricetin-3-O-rhamnoside) and KNA-2 as 2,3-dihyro-3,5,7-trihydroxy-2-(3,4,5-trihydroxyphenyl)chromen-4-one (2,3-dihydromyricetin).
OCH3NH2HCathinone OHOOHOOOHOHOHOOHOHOHH3C123456789101'2'3'4'5'6'1''2''3''4''5''6''KNA-1 OHOOHOOHOHOHOH123456789101'2'3'4'5'6'KNA-2 1
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Cathinone Level, Determination, Khat Leaves, Quantitative, Nmr Methods