Experimental
Plant Material
Flowers of P. obtusa were collected from several
gardens in the Brunei/Muara District of Brunei Darus-
salam in April and May 1996. Voucher specimens
(KAS 434) were made and deposited at Brunei National
Herbarium (BRUN) and the Herbarium of the Uni-
versiti Brunei Darussalam (UBD). Cuttings of a tree of
P. obtusa were also planted in the ground of the Biology
Department of UBD.
Isolation of the Essential Oil
The oil was obtained from fresh ¯owers by hydro-
distillation in a Neo-Clevenger apparatus for 5±6 h.
The moisture content of the ¯owers was determined by
drying in an oven at 508C until no further change in
weight was observed. The density of the essential oil
was determined by using an Anton Parr Model DMA
48, its refractive index by using a Shimadzu Bausch and
Lamb Abbe Refractometer, and its optical rotation by
using a Bellingham and Stanley Digital Polarimeter
Model P20.
Gas Chromatography±Mass Spectrometry
(GC±MS)
GC±MS analysis of the oil was carried out using a
Hewlett-Packard GCD system. An Innowax fused silica
capillary (FSC) column (60 m 0.25 mm, ®lm thick-
ness 0.25 mm) was used with helium as the carrier gas at
1 ml/min. The temperature of the GC oven was kept at
608C for 10 min, and programmed from 608C to 2208C
at 48C/min, held isothermally at 2208C for 10 min, and
®nally programmed to 2408C at 18C/min and kept at
2408C for 20 min. The split ¯ow was adjusted at 50 ml/
min and its split ratio was 50:1. The temperature of the
injector was 2508C and the ionization voltage was
70 eV. The mass range was 10±425 m/z.
Chemical identi®cation of dierent components of
the oil was based on their retention times and com-
parison of mass spectra with those of Wiley GC±MS
Library and TBAM Library of Essential Oil Constitu-
ents. The relative percentage composition of the volatile
compounds was calculated from the total ion chroma-
togram (TIC), assuming that the relative response
factor is equal to 1.
Results and