Terminalia Arjuna (usually simply referred to as Arjuna) is a tree bark that is used medicinally in Ayurveda for the purposes of cardiovascular health pertaining to the heart itself. It has a large variety of bioactives, with the water extract showing promise at improving left ventricle function of the heart without any observable toxicity of side effects when taken at 500mg thrice a day (every 8 hours).
There are numerous human studies conducted on Arjuna bark, although many of them are low in sample size. Nevertheless, the water extract appears to be effective in improving cardiac function in persons who have recently undergone cardiac trauma or injury; Myocardial Infarction is the most commonly researched ailment in this regard. Only one study exists on otherwise healthy persons, but Arjuna showed benefit in improving left ventricle function in an exercise test and the benefits may affect a person regardless of health state.
In animal models, this extract appears to exert protection on cardiac tissue in response to various cardiac insults including beta(2)adrenergic agonists (like ephedrine, although isoproterenol was used in the studies) and catecholamines themselves.
The water extract appears to be effective for improving cardiovascular health, particularly at the level of left ventricle function. The studies in humans are underpowered at this moment in time and only one in healthy humans (preliminary evidence), but all evidence appears to be promising and in the same positive direction. The water extract appears to be quite safe
Other extracts such as ethanolic or acetone, with different bioactives, may not have similar cardioprotective effects (no human trials, but some in vitro evidence suggesting the bioactives are not in these extracts) yet appear to be somewhat cancer protective. Tumor growth in animal models is reduced with either the ethanolic extract or isolated Arjunolic Acid (commonly seen as the main bioactive) as is reduced DNA damage in response to mutagens, and these are attributed to the antioxidative capacity of Arjuna which is comparable to Vitamin C on a per weight basis. Due to the anti-cancer effects of the ethanolic extract having some cytotoxic properties, and LD50 has actually been established with this extract and it is possible that side-effects may occur. Additionally, the anti-cancer evidence is somewhat limited as although cytotoxicity has been established in cancer cells a lack of evidence exists to assess healthy cells (a good anti-cancer drug will be highly selective in killing cancer cells, which Arjuna does, and not healthy cells, which Arjuna has not been sufficiently tested for).
Other possible uses of Arjuna include ulcer protection in the stomach with potency similar to Rantidine in one study (associated with the ethanolic extract), protection to the liver and kidney likely mediated by antioxidative properties (ethanolic extract) and the cardiovascular properties may increase anaerobic cardiovascular performance in healthy persons (with the one study using sprinting as a test) although this last claim has a lone study in support of it and no replication.
Ethanolic extracts have potent antioxidative and potentially potent anticancer effects, but although there are no reported side effects with the ethanolic extracts currently (due to a lack of human interventions) it is theoretically plausible that higher than recommended doses could be harmful related to the anticancer effects (cytotoxicity)