More than 25 different alkaloids could be isolated in kratom, of which the alkaloid mitragynine in Mitragyna speciosa is the most abundant (about 66 %). It was 1907 for the first time isolated by the scientist Hooper. In 1921 Field repeated the analysis in the hope to be able to isolate the active ingredient, after the scientist Wray had sent him a sample of kratom. He also named the alkaloid “mitragynine”. Its structure was first completely identified by Zaccharias et al. (1964). In relevant literature the alkaloid metragynine is responsible for its opium like effect, despite its greater similarity of its structure to psychedelic substances, but without the psychedelic activity. But this has changed in the last years. Recent studies report, that the alkaloid 7-hydroxymitragynine is probably responsible for the first effects after taking kratom.
The most alkaloids, that could be isolated from kratom, are indoles (compounds that contain indole, an aromatic heterocyclic compound; formula: C8H7N) and oxindole (it has the same structure as indole, except a carbonyl group at position C2 of the five-membered ring; formula C8H7NO). The most often occurring alkaloids are mitragynine, payantheine and specioynine (indoles), as well as mitraphylline and speciofoline (oxindoles). Mitragynine and payantheine can only be found in the genus Mitragyna. Other indoles and oxindoles could also be extracted in the alkaloid fractionation, like ajmalicine, akuammine. coryanthedin, mitraversine, rhynchophylline, speciociliatine (that can be found in kratom only), and stipulatines but in very small amounts only.
Differences exist in the composition and amount of the alkaloids between the plant from Thailand and Malaysia. In the plant from Thailand over 20 different alkaloids could until recently be isolated, they are of the coryanthe type, oxindole-derivatives included. The most abundant alkaloids of these are: mitragynine (66.2 %, based on the raw product), payantheine (8,6 %), speciogynine (6,6 %), 7a-hydroxy-7H-mitragynine (2%), and speciociliatine (0,8 %).
On the other hand in the Malaysian plant these five alkaloids, mitragynine, speciogynine, speciociliatine, payantheine, and 7-hydroxymitragynine, could be isolated, that were likewise found in the plant from Thailand. Mitragynine is here also the highest ingredient, however it occurs in the Malaysian plant in a much smaller amount, only 12 %, in comparison to the plant from Thailand. In the Malaysian plant small amounts of mitragynaline and pinoresinol could also be isolated from young leaves. In addition three indole alkaloids could be found, mitalactonale, mitrasulgynine, and 3,4,5,6-tetradehydromitragynine (Takayama, 2004).
In the Papua New Guinea plant the alkaloids mitragynine, speciogynine,, speciociliatine, payantheine, specionoxeine and isospecionoxeine could be determined.
The amount of the alkaloids in the respective plant however varies with timing and location. Shellard et al. (1974) documented for plants of the same species geographical differences in the alkaloid content, as well as differences from month to month in the alkaloid content of the same plant.