Variation of Alkaloid Content in Erythroxylum coca Leaves from Leaf Bud to Leaf Drop

Abstract

A sequential study describing the content (%) of alkaloids in leaves of Erythroxylum coca var. coca Lam. from leaf bud development to leaf drop has not previously been conducted. The length of time the leaf resides on the plant and its concurrent metabolic activity also has not been defined. In the present study, cocaine, methyl ecgonine, hygrine, tropinone, trans -cinnamoylcocaine, cis-cinnamoylcocaine, tropacocaine and cuscohygrine were monitored to determine: (1) their content and patterns of accumulation from leaf bud to leaf drop; (2) the time leaves resided on the plant; and (3) whether leaves were metabolically active until leaf drop. E. coca plants were grown in a controlled environment for 37 months. Leaves similar in chronological age were extracted and analysed for alkaloid content by gas chromatography (GC) and gas chromatography/mass spectrometry (GC/MS). Cocaine was highest in 7 d old rolled leaves (0·75%) and declined to 0·39% at leaf drop. Cocaine, methyl ecgonine, hygrine, tropinone, trans -cinnamoylcocaine, cis-cinnamoylcocaine, cuscohygrine and tropacocaine content in 35 d old (mature) leaves was 0·61, 0·59, 0·68, 0·08, 0·31, 0·55, 0·52, and 0·05%. respectively. Cocaine, methyl ecgonine, hygrine, cis -cinnamoylcocaine, and cuscohygrine displayed a gradual decline from week 2 to week 36 of leaf duration. Tropinone and tropacocaine were the least abundant of the alkaloids monitored. Cis-cinnamoylcocaine content exceeded cocaine at week 12, 16, and weeks 19 to 23 of leaf duration. Trans -cinnamoylcocaine was highest in rolled leaves (week 1) and in expanded leaves after week 30. The monitored alkaloids appeared to be part of the metabolically active pool of the leaf. Leaves remained on the E. coca plants for 36 weeks.