The cocaine alkaloid content of the E. coca and the E. novogranatense species
also serves to distinguish between these species and the many other species
of wild coca that grow in Latin America. These other species contain much
lower levels of cocaine alkaloid. The usual cocaine alkaloid content of a
sample of coca leaf material is between 0.1 and 0.8 percent. The cocaine
alkaloid content can go much higher, however, as was shown in one sample of
coca leaf from the Chapare region in Bolivia that measured 1.2 percent. Coca
grown on the upper slopes of the Andes also contain more cocaine alkaloids
than coca grown in low-lying areas. It is therefore believed that the best
quality coca is grown at higher altitudes.
got it from here...
http://www.druglibrary.org/schaffer/GovPubs/cocccp.htm
