A number of medicinal plants from India, China and Japan are used for diabetes. One of the most effective plant compounds discovered is corosolic acid found in the leaves of the banaba (lagestroemic speciosu) tree.
Corosolic acid acts like insulin, the hormone that naturally increases glucose transport activity across cell membranes, thus facilitating the lowering of blood sugar. Clinical studies in the US and Japan show that corosolic acid is safe and effective in lowering blood sugar levels in pre-diabetes and type 2 diabetes.