In 1993, a group of scientists from Hiroshima University used an Ehrlich ascites tumor cell line coupled with a bioassay guided fractionation to screen compounds isolated by HPLC from banaba extract in order to identify the effective antidiabetic component (21) . Corosolic acid (2a-hydroxyursoloic acid) was identified as the effective compound in the methanol extract of banaba leaves in a glucose uptake assay ( Fig. 2A, 21) . However, this result should be considered with caution since the tumor cell line used in this study is a very unusual and unconventional cell line for diabetes studies or antidiabetic compound screening. Furthermore, the result could not explain the discrepancy that both the banaba water extract and the methanol extract were active in antidiabetic and anti-obesity animal studies since corosolic acid only exists in the methanol extract (19) (20) (21) . Realizing the potential problems associated with the cell line selection and assay method, the researchers acknowledged in a later publication that corosolic acid 'could not represent the whole activity of the banaba extract' (22) . Consequently, the researchers switched their cell model from the original tumor cells to a natural cell target of insulin, adipocytes, in order to allow for the 'isolation and the identification of more active compounds using the improved methodology' (22) . After HPLC purification, ellagitannins were identified in the water extract of banaba as the activators of glucose transport in fat cells with a glucose uptake assay (22) . One of the most potent ellagitannins was named 'Lagerstroemin' (Fig. 2, 22) .