Abstract
Mitragyna speciosa (K.) H. (Kratom) is a tree that possesses stimulant and opioid-like analgesic effects, and is indigenous to Southeast Asia and Indochina, where it has seen widespread use for hundreds of years. The principal pharmacologically active alkaloids in kratom leaves include mitragynine (MG), 7-hydroxymitragynine (HMG), speciociliatine (SC), speciogynine (SG) and paynantheine (P). The pharmacological effects induced and their potency can vary dramatically according to variations in the proportions of alkaloid compounds present, which are related to geographic origin, stage of maturity and ecotype. Much of the analgesic and opiate-like psychoactive effect of kratom has been associated with the MG and HMG detected in M. speciosa (K.). H. Five different strains of M. speciosa (K.) H., which present differing vein colours and geographic origin, have been studied herein; red vein strains from Thailand, Malaysia and Bali, named Red Thai, Red Malay and Red Bali, a white vein strain from Borneo (White Borneo) and a green vein strain from Malaysia (Green Malay) were included in the study. Plant leaves were extracted under magnetic stirring at room temperature in a MeOH/H2O 1:1 mixture. Purified alkaloids were isolated in a number of organic extraction steps, from either aqueous basic or acidic phases, that culminated in precipitation (yields between 0.94 and 1.43%). These samples have been analysed using HPLC-DAD, HPLC-MS, HPLC-MS/MS and GC-MS to optimize the identification and quantification of the principal alkaloids present in the different strains. 24 alkaloids were detected in Red Bali whereas 11 compounds were found in the other varieties. Red Thai, Red Bali, Green Malay and White Borneo strains had a higher w/w percentage for MG than for P, while P was more abundant in Red Malay. The Green Malay variety (GMK) showed the highest w/w percentages for MG and total alkaloids in its extracts (59.7 and 94.9% respectively). The Green Malay variety was therefore chosen for in vivo pharmacological studies. The Green Malay extract has shown remarkable and significant antinociceptive and anti-inflammatory activity in mouse hot plate and carrageenan-induced paw edema tests.