Plant material
Fruits of Piper sarmentosum were collected from Kanchanaburee
province, Thailand. A voucher specimen
(No. 0039 (RU)) is deposited at the Faculty of Science,
Ramkhamhaeng University.
2.3. Extraction and separation
The pulverized, dried fruits of Piper sarmentosum
(2.39 kg) were extracted successively with hexane and
MeOH in a Soxhlet apparatus. After removal of solvent in
vacuo, the hexane extract (70.7 g) was subjected to quick
CC (silica gel) eluting with hexane, hexane–CHCl3, CHCl3,
CHCl3–MeOH and MeOH (in order of increasing polarity)
to give 6 main fractions (H1–H6). Fraction H2 was rechromotographed
on silica gel column using a gradient solvent
system of hexane, hexane–EtOAc, EtOAc, EtOAc–MeOH
and MeOH to obtain 13 subfractions (H2.1–H2.13). Fraction
H2.2 was further purified by silica gel CC using hexane
as eluent to give 11 (284 mg) whereas fraction H2.7 yielded
a mixture of 13 and 14 (13 mg). Fraction H2.9 was rechromatographed
on silica gel column using EtOAc–hexane
(15:75) as eluent to afford 1 (122 mg). Fraction H3 was
separated by silica gel CC using a hexane–EtOAc step
gradient to obtain 24 subfractions (H3.1–H3.24). Filtration
of fractions H3.4 and H3.17 yielded 9 (5 mg) and
2 (91 mg), respectively. Fractions H4 and H5 were separately
fractionated into 12 subfractions each (H4.1–H4.12
and H5.1–H5.12, respectively) on silica gel columns using
a gradient solvent system similar to that of fraction H2.
Purification of fraction H4.4 by chromatography on silica
gel and elution with EtOAc–hexane (15:85) afforded 3
(6 mg) whereas fraction H4.6 yielded 4 (1.28 g). From fraction
H5.11, 5 (14 mg) was isolated by silica gel CC using
EtOAc–hexane (25:75) as eluen