DIURNAL FLUCTUATIONS OF COCAINE AND POTENTIAL PRECURSORS IN LEAVES OFERYTHROXYLUM-COCA

Cocaine is abundant in leaves of Erythroxylum coca var. coca Lam. Cons equently, cocaine and two of its early biosynthetic precursors were mo nitored for 24 h to determine whether they fluctuated diurnally. E. co ca was grown under controlled environmental conditions in a growth cha mber in soil at pH 3.5. After 17.5 months of growth, leaves not less t han 35 days old were harvested every 2 and 4 h for 24 h for arginine, phenylalanine and cocaine content, respectively. The content of cocain e was determined by GC/MS and amino acid content by HPLC. Diurnal fluc tuation of cocaine occurred during the 24 h cycle. Cocaine was highest in leaves of E. coca at 8 and 16 h where its content was 7.67 and 9.4 5 mg.g(-1) dry weight, respectively. Arginine and phenylalanine in lea ves of E. coca also displayed diurnal rhythmic pat terns of fluctuatio n. The content of arginine declined from hours 6 to 12 and increased t o the highest content at 13 h (21.8 mg.g(-1) dry weight). Overall, phe nylalanine content was lower than arginine, but had two peak periods o f accumulation during the 24 h cycle, occurring at 8 and 14 h. The con tent of phenylalanine in leaves of E. coca during the peak hours was 6 .98 and 6.54 mg.g(-1) dry weight, respectively.