ABSTRACT: The methanolic extract of the marine sponge
Ircinia felix has yielded nine novel fatty acid esters, (7E, 12E,
18R, 20Z)-variabilin (5Z, 9Z)-22-methyltricosadienoate, (7E,
12E, 18R, 20Z)-variabilin (5Z, 9Z)-tetracosadienoate, (7E, 12E,
18R, 20Z)-variabilin hexadecanoate, (7E, 12E, 18R, 20Z)-vari-
abilin 10-methylhexadecanoate, (7E, 12E, 18R, 20Z)-variabilin
15-methylhexadecanoate, (7E, 12E, 18R, 20Z)-variabilin 14-
methylhexadecanoate, (7E, 12E, 18R, 20Z)-variabilin 9-octade-
cenoate, (7E, 12E, 18R, 20Z)-variabilin octadecanoate, and (7E,
12E, 18R, 20Z)-variabilin 2,11-dimethyloctadecanoate, along
with the recently described (7E, 12E, 18R, 20Z)-variabilin 11-
methyloctadecanoate. The characterization of the new fatty
acids (5Z, 9Z)-22-methyltricosadienoic and 2,11-dimethyloc-
tadecanoic acids is also described. The chemical structures
were determined by extensive spectroscopic, chromatographic,
and chemical analyses.
Lipids 32, 565–569 (1997).
Marine sponges of the genus Ircinia (order Dictyoceratida)
are known as common sources of furanosesterterpene tetronic
acids and of linear C
21
furanoterpenes (1,2). During the
course of our studies on I. felix, I. campana, and I. strobilina
occurring in the Colombian Caribbean coast, we recently re-
ported (3,4) on the occurrence of (7E, 12E, 18R, 20Z)-vari-
abilin as the major antimicrobial furanosesterterpene tetronic
acid in the three Ircinia sponges examined, followed by
medium levels of (8E, 13Z, 18R, 20Z)-strobilinin, (7E, 13Z,
18R, 20Z)-felixinin and lesser amounts of (8Z, 13Z, 18R,
20Z)-strobilinin and (7Z, 13Z, 18R, 20Z)-felixinin. More re-
cently we detected in I. felix a complex mixture of fatty acid
esters of furanosesterterpene tetronic acids, of which only the
novel variabilin 11-methyloctadecanoate has so far been re-
ported (5).
To continue our studies on I. felix collected in the Colom-
bian Caribbean, we reisolated the furanosesterterpene tetronic
acid fatty acid ester mixture in order to identify the rest of the
esters present in this marine sponge. Thus, in this paper we
report on the isolation of nine novel fatty acid esters of (7E,
12E, 18R, 20Z)-variabilin as major components of the above-
mentioned mixture along with two new fatty acids, whose
chemical structures were determined by spectroscopic, chro-
matographic, and chemical analyses.
MATERIALS AND METHODS
Materials. All solvents used were of high purity at purchase
(Merck, Darmstadt, Germany) and were redistilled before
use.
Samples. Ircinia felix was collected by SCUBA at Santa
Marta Bay on the Caribbean coast of Colombia, at a depth of
15–20 m. Voucher specimens have been deposited in the ref-
erence collection of the Instituto de Investigaciones Marinas
de Punta Betín, Colombia. Local populations have been de-
scribed by Zea (6).
Variabilin fatty acid esters extraction. A sample of thawed
sponge (1.8 kg) was soaked in methanol (2 L) for 24 h and
filtered. After concentration of the extract, it was partitioned
between ethyl acetate/water (2:1, vol/vol). The organic layer
was dried, and removal of the solvent yielded a brown residue
(19.4 g). Part of this residue (4.4 g) was subjected to column
chromatography on silica gel, eluting with hexane/ethyl ac-
etate (5:1, vol/vol) to give 19 mg of crude variabilin fatty acid
ester mixture. Although this fraction was detected as a single
spot by thin-layer chromatography (TLC) analysis on silica
gel, reversed-phase high-performance liquid chromatography
(RP-HPLC) revealed it to be a complex mixture of esters
which were separated on a preparative ODS HPLC column
and identified on the basis of spectral, chromatographic, and
chemical evidence.
High-performance liquid chromatography (HPLC).
Preparative HPLC was performed on a Shimadzu Techno-Re-
search PREP-ODS(H) column (250 × 20 mm i.d., 5 µm)
using a Shimadzu Liquid Chromatograph 6A (Kyoto, Japan)
and a Shimadzu SDD-6A ultraviolet (UV)-visible detector
monitoring at 270 nm, with methanol as mobile phase (flow
rate 5 mL/min). Fractions were collected as indicated by dot-
ted lines in Figure 1.
Copyright © 1997 by AOCS Press 565 Lipids, Vol. 32, no. 5 (1997)
1
Current address: Facultad de Química Farmacéutica, Universidad de Antio-
quia, AA 1226, Medellín, Colombia.
*To whom correspondence should be addressed.
Abbreviations: ECL, equivalent chain length; EI–MS, electron impact mass
spectrometry; FAB–MS, fast atom bombardment–MS; GC, gas chromatog-
raphy; GC/MS, GC coupled to MS; HPLC, high-performance liquid chro-
matography; NBA, nitrobenzylalcohol; NMR, nuclear magnetic resonance;
RP-HPLC, reversed-phase high-performance liquid chromatography; RT, re-
tention time; TLC, thin-layer chromatography; UV, ultraviolet.
COMMUNICATION
Novel Fatty Acid Esters of (7E, 12E, 18R, 20Z)-Variabilin
from the Marine Sponge Ircinia felix
Alejandro Martínez
a,1
, Carmenza Duque
a,
*, and Yoshinori Fujimoto
b
a
Departamento de Química, Universidad Nacional de Colombia, AA 14490 Bogotá, Colombia,
and
b
Department of Chemistry, Tokyo Institute of Technology, Meguro, Tokyo, Japan