Robert B. (Temple University School of Pharmacy, Philadelphia, Pennsylvania, USA) Raffa 
Kratom and Other Mitragynines [PDF ebook] 
The Chemistry and Pharmacology of Opioids from a Non-Opium Source

Opioids such as morphine, codeine, and oxycodone are extracts or analogs isolated from a single source: the opium poppy. For a long time, it was believed to be nature”s only source of opioids. But it now appears that biological diversity has evolved an alternative source of opioid compounds-those derived from the plant Mitragyna speciosa. This plan