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
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.