Most of the alkaloids identified in Mitragyna speciosa Kratom are Yohimbe-type indoles and oxindoles. The most abundant alkaloids consist of three indoles and two oxindoles, and some indoles such as mitragynine, paynanthine and others are unique to the Mitragyna speciosa plant.

Other indole alkaloids present are found in the whole leaf of the Mitragyna
plant. Two of particular interest are corynantheidine another μ-
opioid antagonist also found in Yohimbe, as well as 9-hydroxycorynantheidine
a partial μ-opioid agonist, which makes for an interesting combination between full agonists (such as 7-hydroxymitragynine and mitragynine) with an
antagonist or partial agonist – and this alkaloidal balance probably plays a
significant role in Mitragyna speciosaKratom’s complex opiate like action, yet without developing the full addictive potential of opiates.

Other active alkaloids present in Mitragyna speciosa Kratom include
raubasine (best known from Rauwolfia serpentina) paynanthine,
speciogynine, mitraphylline, mitraversine, ajmalicine, and several other less
abundant alkaloids.

Ajmalicine (also called raubasine), is a Mitragyna speciosa alkaloid which is also found in Rauvolfia serpentina (Indian snakeroot) and Catharanthus roseus (Madagascar periwinkle), and has multiple pharmacological activities. Ajmalicine/raubasine inhibits platelet aggregation through an inhibitory action on the release reaction of the platelets. It also has some sedative and anticonvulsive properties due to agonist activity at the [3H] flunitrazepam benzodiazepine receptor, and increases the availability of oxygen in the brain, which has led to its use in cognitive disorders in the elderly and in stroke ischemia.

Ajmalicine/raubasine also acts as an antiadrenergic, through the blocking of alpha-1-adrenergic receptors, inducing a lowered blood pressure and acting as a diuretic through the relaxation of smooth muscle. Mitragyna speciosa Kratom also shares another indole with Catharanthus roseus: tetrahydroalstonine, which is known to lower blood sugar levels and acts as a blocker at the alpha-2-adrenergic receptors.

Mitragyna speciosa Kratom contains several alkaloids found in the South-American medicinal plant Uncariatomentosa (cat’s claw/uña de gato) which are thought to play a beneficial role on the immune system and lower blood pressure. The most predominant of these alkaloids is mitraphylline, which has shown activity as a vasodilator and in lowering blood pressure, and is also a diuretic and muscle relaxer (myorelaxant). A study has indicated that it might increases memory retention performance in animals treated with amnesic drugs.

Kratom also contains the Uncaria alkaloid isopteropodine, which has been shown to be the most effective immunostimulant of this alkaloid group, as well as rhynchophylline, which also lowers blood pressure by a blocking of the voltage-dependent calcium and potassium channels, dilating peripheral blood vessels, and lowering heart rate. Rhynchophylline also has cardiac antiarrhythmic properties, lowers cholesterol and prevents blood clots by inhibiting platelet aggregation and thrombosis. It also has anti-inflammatory and anti-pyretic properties.

Rhynchophylline, as a calcium channel blocker, (and reduces NMDA-induced current) could be playing a considerable role in modifying the development of opioid action related addiction mechanisms.

Speciophylline (also known as uncarine-D) has been used against leukemia, shown cytotoxic activity against leukemic cells like isomitraphylline, more effective against U-937 than HL-60.

Rotundifoline is another Uncaria alkaloid found in Kratom, but it is not know if it has any activity in Kratom. Corynoxine A and corynoxine B reduce locomotor activity in mice, apparently due to a mediating activity in the dopaminergic system.

Corynoxeine (not to be confused with corynoxine A and B) is an oxindole which has calcium channel antagonist activity similar to verapamil.

Mitragyna speciosa also contains epicatechin, a powerful antioxidant which also found in dark chocolate, green tea, cranberry juice, a polyphenol (the cis-isomer of catechin) which is closely related to the EGCG that gives a wide spectrum of beneficial effects. Epicatechin reduces free radicals in the blood, hence reducing some cancer risks, and acts as a powerful antioxidant which helps prevent fat cells from oxidizing and clogging arteries.

Epicatechin has demonstrated some ability to inhibit growth of pathogenic bacteria such as E. coli and staphylococci, showing anti-viral properties and inhibiting the ability of viruses to enter and infect cells. It helps with urinary tract infections by reducing bacteria's ability to stick to the cell walls of the urinary tract. Epicatechin keeps blood sugar levels lower by inhibiting intestinal glucose absorption, and also through its insulin mimicry, protecting erythrocytes in a similar manner, and also inhibits alpha-amylase, preventing the digestion of starch into absorbable glucose.