The leaves of Lagerstroemia speciosa L. (Lythraceae)
were harvested in March from Luzon Island in the Philippines.
Permit to collect and export plant material was given
by The Foreign Trade Statistics of the Philippines under
Volume 2—Export Food and Live Animal No. 074.10 on 2
February 1999. The voucher specimen (#Lag-0037) is kept
at the Department of Medicine, Hiroshima University, Japan.
The leaves were dried, extracted with 80% (w/w) aqueous
ethanol at 80 ◦C for 1.5 h, cooled to room temperature, then
filtered. The extract was treated with activated carbon to remove
chlorophyll, filtered and concentrated under reduced
pressure to give a dry solid, which was shown by HPLC
to contain 3% corosolic acid. The HPLC conditions: ODS
C18 column (4.6 mm×150 mm); 35:65 (v/v) water containing
0.1% trifluoroacetic acid:acetonitrile as a mobile phase;
flow rate of 1.0 ml/min; and UV detection at 210 nm. The
extract was standardized to contain 1.0% corosolic acid to
give GlucosolTM.
GlucosolTM was provided to subjects in either a soft
gelatin capsule as a suspension in a vegetable oil-base or in
a two-piece hard gelatin capsule as a powder in rice-bran
base.