Lagerstroemia speciosa L. is distributed all over the Philippines. The leaves of this plant are called "Banaba", and used as an anti diabetic, the decoction has been clinically tested and found to reduce blood sugar.

The bioactive McO11 extract of banaba was fractionated and subjected to column chromatography. The bioactivity of each fraction was monitored at each stage of the isolation process. From the active McO11 fraction eluded from a Diaion HP-20 chromatography column, compounds 1 and 2 were isolated by silica-gel column chromatography in yields of 0.01 and 0.0016%, respectively. Compounds 1 and 2 were identified by means of NMR as known tritepenes, colosolic acid (2a-hydroxyursoloic acid) and maslinic acid (2a-hydroxyoleanolic acid), respectively.

The bioactivity of 1 and 2 was measured by the above method. Colosolic acid (1) showed a significant glucose transport-stimulating activity at a concentration of 1mm, while 2 were inactive (Table III).

The hypoglycemic effect of 1 has recently been reported in normoglycemic rats following oral administration. This evidence strongly suggest that our in vitro bioassay is closely related to the hypoglycemmic effect and maybe used as a first screening method for anti-diabetic substances without the need for any animals, as in an in vivo assay. Examinations of the correlation of both activities and a further search for active substances in other plants are in progress.