Krizevski, R., Department of Aromatic, Medicinal and Spice Crops, Newe Ya'ar Research Center, Agricultural Research Organization, P.O. Box 1021, Ramat Yishay, 30095, Israel
Dudai, N., Department of Aromatic, Medicinal and Spice Crops, Newe Ya'ar Research Center, Agricultural Research Organization, P.O. Box 1021, Ramat Yishay, 30095, Israel
Bar, E., Department of Aromatic, Medicinal and Spice Crops, Newe Ya'ar Research Center, Agricultural Research Organization, P.O. Box 1021, Ramat Yishay, 30095, Israel
Lewinsohn, E., Department of Aromatic, Medicinal and Spice Crops, Newe Ya'ar Research Center, Agricultural Research Organization, P.O. Box 1021, Ramat Yishay, 30095, Israel

Khat (Catha edulis Forsk., Celastraceae) is a perennial shrub that was introduced to Israel by Yemenite immigrants. Khat young leaves are chewed as a stimulant. The main stimulating active principles in this plant are the phenylpropylamino alkaloids (-)-cathinone [(S)-α-aminopropiophenone], (+)-cathine [(+)-norpseudoephedrine] and (-)-norephedrine. A novel GC-MS analysis method for the quantitative determination of phenylpropylamino alkaloids and their putative precursor 1-phenyl-1,2-propanedione in khat leaves was developed. We found a marked diversity in the phenylpropylamino alkaloids content and composition in 9 different accessions originated in seedlings and in the commercial cultivar "Mahanaim". The highest 1-phenyl-1,2-propanedione and (-)-cathinone levels occur in young leaves, the part traditionally chewed for its psycho-stimulating properties. Older leaves lack (-)-cathinone but contain the less active (+)-cathine and (-)-norephedrine. Young stems and flowers also contain 1-phenyl-1,2-propanedione, (-)-cathinone, (+)-cathine and (-)-norephedrine. We report the presence of a (-)-cathinone reductase in khat leaves capable of reducing (-)-cathinone to (+)-cathine in the presence of NADPH. We propose that (-)-cathinone is a biosynthetic precursor of (+)-cathine and (-)-norephedrine in khat leaves. © 2007.