American Journal of Analytical Chemistry, 2011, 2, 989-995
doi:10.4236/ajac.2011.28116 Published Online December 2011 (http://www.SciRP.org/journal/ajac)
Characterization of Chemical Constituents of
Luffa operculata (Cucurbitaceae)
Cléia Rocha de Sousa Feitosa1,3, Robério Costa da Silva1, Raimundo Braz-Filho2,
Jane Eire Silva Alencar de Menezes4, Sônia Maria Costa Siqueira5, Francisco José Queiroz Monte1
1Programa de Pós-Graduação em Química-DQOI-CC, Universidade Federal do Ceará, Fortaleza, Brazil
2Universidade Estadual do Norte Fluminense Darcy Ribeiro, Campos dos Goytacazes, Brazil
3Universidade Estadual do Ceará, Faculdades de Educação de Crateús, Fortaleza, Brazil
4Universidade Estadual do Ceará, Itapipoca Fortaleza, Brazil
5Universidade Estadual do Ceará, e campos do Itaperi, Fortaleza, Brazil
Received August 4, 2011; revised September 15, 2011; accepted September 28, 2011
Abstract
A mixture of new ceramides (1, 2, 3, 4 and 5) together with a binary mixture of ceramides with long chain
alkyl (6 and 7), triterpenoid (10) and steroids (11 and 12) have been isolated from bark of the fruits and of
the stems of Luffa operculata (Cucurbitaceae). The structures were elucidated by comprehensive spectro-
scopic analysis including 1H and 13C NMR, DEPT (distortionless enhancement by polarization transfer),
COSY (correlated spectroscopy), HMQC (heteronuclear multiple quantum coherence), HMBC (heteronu-
clear multiple bond connectivity), IR (infrared), HR-ESI-MS (electrospray ionization-high resolution mass
spectra) and LR-MS (low resolution electron ionization mass spectra) experiments. All the ceramides are
reported for the first time in Cucurbitaceae and this is the first report of the rare triterpene 10 isolated from
Luffa operculata. The ceramides 6 and 7 showed a high acetylcholine esterase inhibitory effect.
Keywords: Cucurbitaceae, Ceramides, Triterpenes, Spectroscopic Data
1. Introduction
As a part of our continuing chemical studies on plants of
Cucurbitaceae family, we have investigated the bark of
the fruits and the stems of Luffa operculata specie. L.
operculata Cogn. (Cucurbitaceae), locally known as
“cabacinha”, a perennial shrub widely distributed in
Northeastern Brazil where an aqueous solution from its
fruits has been used in popular medicine for the treat-
ment of sinusitis [1]. In the previous paper [2], we re-
ported the isolation and structure elucidation of triper-
penes cucurbitane type from these fruits. In this paper,
we report the isolation and structure elucidation of cera-
mides (1-5, 6 and 7), triterpene oleanane type (10) and
steroids (11 and 12) from the bark of the fruits and stems
of this plant. In plants, recent studies indicate that cera-
mides may be involved in signal transduction, membrane
stability, host-pathogen interactions, and stress responses
[3].The compound 6 and 7, as well as the steroids mix-
ture (12), showed an acetylcholine esterase inhibitory
effect. Inhibition of acetylcholinesterase (AchE) is used
as a strategy for the treatment of Alzheimer's disease
(AD), a neurodegenerative malady characterized by cog-
nitive impairment and personality changes. One of the
most promising approaches for treating this disease is to
enhance the acetycholine level in rain using acetylcho-
line esterase (AChE) plant-derived inhibitors [4]. In this
work we report an evaluation of the cholinesterase inhi-
bition effect of the ceramides 6 and 7 following the
methodology of Elmann, adapted by Rhee [5] for the
layer chromatography (TLC).
2. Materials and Method
2.1. General Procedures
1H and 13C NMR spectra were recorded on Bruker DPX
300 and DRX 500 spectrometers in CDCl3, with TMS as
an internal standard. DEPT and all 2D experiments
(COSY, HMQC and HMBC) with standard Bruker pulse
sequence; IR spectra were carried out on Perkin-Elmer
2000 series FT-IR; electrospray ionization mass spectra

C. R. de S. FEITOSA ET AL. 990
(HR-ESI-MS) obtained in mass spectrometer model
LCMS-IT-TOF (225-07100-34, Shimadzu) and on a
QP5050 (Shimadzu) instrument at 70 eV for low resolu-
tion; melting point were measured on Mettler Toledo
FP90 apparatus, uncorrected; the spots were visualized
by spraying with a mixture of vanillin-perchloric acid
ethanol.
2.2. Extraction and Isolation of Constituents
Luffa operculata stems were collected in Acarape County,
Brazil and identified in the Departamento de Biologia do
Centro de Ciências da Universidade Federal do Ceará
(UFC). A voucher specimen (N˚ 43.056) was deposited
at Departamento de Biologia (UFC) Prisco Bezerra Her-
barium.The air-dried stems (935 g) were powdered and
extracted at room temperature with hexane and EtOH.
The hexane extract (4.1 g) was subjected to column
chromatography (CC) on silica gel (Si gel) 60 (230 - 400
mesh) using hexane, CH2Cl2, EtOAc and MeOH as sol-
vents. The CH2Cl2 fraction (2.56 g) was further subjected
to CC on Si gel 60 (230 - 400 mesh) to yield a material
(17.5 mg) white greasy (1 - 5) and 11 (102 mg). The
AcOEt fraction (4.95 g) of EtOH extract (22.5 g) was
successively chromatographed on Si gel column to afford
10 (7.5 mg) as white powder. The air-dried bark of fruits
(195.8 g) were powdered and extracted at room tem-
perature with hexane and EtOH. The EtOH extract (10.5
g) was subjected to CC on silica gel 60 (230 - 400 mesh)
using CH2Cl2, EtOAc and EtOH as solvents. The CH2Cl2
fraction (0.29 g) was successively chromatographed on
Si gel column to afford 12 (21 mg) as a white powder,
while the AcOEt fraction (0.59 g) after successively
chromatographed on Si gel column afforded 6 and 7
(24.5 mg) a white solid.
3. Results and Discussion
The CH2Cl2 fraction of the hexane extract of the stems of
L. operculata was chromatographed on silica gel column
to yield a white greasy material. Its IR spectrum dis-
closed bands due to methylene and methyl (γmax 2923/
2853 cm–1 and δmax 1462/1380 cm–1), carbonyl (γmax 1737
cm–1) groups, as well as bands of C - O/C - N (γmax 1172
cm–1) bounds. The LR-MS displayed a cluster of four
14-amu-apart ion peaks at m/z 311, 297, 283, 269 and
255 indicative of a mixture of homologous compounds
(Scheme 1). In agreement, the NMR data (Table 1) re-
vealed signals due to methylene groups [intense and
broad signal at δH 1.29 - 1.34; several peaks at δC 23.46 -
34.89 (very high peak at δC 29.85)], as well as signals to
one primary methyl group (δH 0,89, t, 6.7 Hz; δC 14.80)
all characteristic of a long alkyl chain. The methylene
hydrogens at δH 2.39 [t, 7.3 Hz; δC 34.89 (methylene
carbon alfa to carbonyl)] showed 2J and 3J HMBC cor-
relations with the carbons at δC 174.20 (C = O), 32.64
(methylene carbon beta to carbonyl) and 30.26 (methyl-
ene carbon gama to carbonyl) and allowed to establish
the partial structure I.
CH3-(CH2)n-CH2-CH2-CH2-C=O
I
In addition, the 1H and 13C spectra exhibited signals
due to two other methylene groups (δH 4.38, t, 4.9 Hz,
2H; δC 64.67 and δH 3.66, t, 5.2 Hz, 2H; δC 66.76) and to
a secondary gem-dimethyl group (δH 1.12, d, 6.0 Hz, 6H;
δC 22.71 and δH 3.57, m, 1H; δC 72.40) and allowed to
suggest the partial structure II.
n +M

m/z Fragmentos m
14 397 311 18
13 383 297 17
n+3
3'
n+1
n+2
4
4
1
2
1'
2'NO
O
H
3
4´
n
12 369 283
NH2
O
m
16
11 355 269 15
10 341 255 14
CH3CHCH3
m/z 43
O
m/z 86m/z 73
O
Scheme 1. Structures for the amides 1-5.

C. R. de S. FEITOSA ET AL.991
Table 1. 13C (125 MHz) and 1H (500 MHz) data of compounds 1 - 5 in pyridine-d5, δ in ppm, J in Hz and multiplicities, in
parenthesis.
No. 1 - 5
C δC δH 2,3 JCH
1’ 174.20 - H-1; H-2’; H-3’
CH
3 72.40 3.57 (m) H-4; H-2
CH2
1 64.67 4.38 (t, 4.9) H-2
2 66.76 3.66 (t, 5.2) H-1
2’ 34.89 2.39 (t, 7.3) H-3´
3’ 25.81 1.67 (m) H-2´
4’ 30.26 1.29 - 1.34 (m)
5’-n 29.85 - 30.51 1.29 - 1.34 (m) -
n + 1 32.64 1.29 - 1.34 (m) 3H-n + 3
n + 2 23.46 1.29 - 1.34 (m) -
CH3
4 22.71 1.12 (d, 6.0) -
n + 3 14.80 0.89 (t, 6.7) H-2; H-4
N-CH2-CH2-O-CH (C H 3)2
II
In the 1H - 1H COSY spectrum, the mutual correla-
tions between the signals at δH 4.38 and 3.66, as well as
between the signals at δH 1.12 and 3.57, supported the
fragment II. The linkage of theses partial structures (I
and II) to each other was based on additional long-range
connectivities observed between the hydrogens at δH
4.38 (-NCH2-) and the carbon atom in δC 174.20 (C = O)
in the 1H-13C HMBC spectrum and resulted in the gen-
eral structure III, corresponding to amides mixture. Oth-
ers correlations in the HMBC spectrum were assigned in
the Table 1.
n+3
3'
n+1
n+2
4
4
1
2
1'
2'NO
O
H
3
4´
n
III
Finally, the fragments in the mass spectrum due to the
peaks at m/z 311, 297, 283, 269 and 255 obtained by
McLafferty rearranjement from molecular ion peaks at
m/z 397, 383, 369, 355 and 341 (observed at 395, 381,
367, 353 and 339, respectively), respectively, allowed
the possible structures for the amides 1 - 5 (Scheme 1),
unknown ceramides up to date. Others important peaks
as m/z 86 (100%), 73 and 43 all are in agreement with
the proposed structures (Scheme 1).
1 n = 14M+• 397N-(2-isopropoxy-ethyl)eicosamide
2 n = 13M+• 383N-(2-isopropoxy-ethyl)nonadecanamide
3 n = 12M+• 369N-(2-isopropoxy-ethyl)octadacanamide
4 n = 11M+• 355 N-(2-isopropoxy-ethyl)heptadacanamide
5 n = 10M+• 341N-(2-isopropoxy-ethyl)hexadecanamide
The AcOEt fraction of the EtOH extract from barc
fruit of L. operculata was chromatographed on silica gel
column to afford a white solid whose high-resolution
high-resolution ESI mass spectrometry in the negative
mode displayed two 14-amu-apart quasimolecular ion
peaks [M-H]- at m/z 736.5277 and 722.3396, indicative
of a binary mixture of homologous compounds. The IR
spectrum of this solid disclosed bands at 3336/3218,
2918/2849 and 1621 cm–1 suggestive of OH and/or NH,
CH3/CH2 and C = O groups, respectively, as well as
bands at 1070/1025 cm–1 of C-O/C-N bound; further

C. R. de S. FEITOSA ET AL. 992
bands at 1544, 1466 and 750 cm–1 were attributed to NH,
CH3/CH2 and CH2 groups, respectively. The 13C and
DEPT NMR spectra (Table 2) showed several aliphatic
methylenes (δC 23.28 - 36.17) and methyl terminal signal
(δC 14.55) which constructed a long alkane chain. These
spectra also revealed the presence of six methine [δC
53.42; three oxygenated (δC 72.75, 73.26 and 77.32) and
two olefinic (δC 131.16 and 131.04)] carbons. In addition,
signals at δC 62.36 and 175.64 indicated an oxymethyl-
ene carbon and an ester or amide carbonyl, respectively.
The 1H NMR spectrum also revealed characteristic sig-
nals for long alkyl chains (δH 1.27 - 1.33) as well as a
signal at δH 8.61 compatible with hydrogen of secondary
amide (RCONHR’) which, was further substantiated by
its 13C NMR (δC 175.64) and IR (1621 and 1544 cm–1)
spectra. In the 1H-1H COSY spectrum, the amide hydro-
gen with resonance at δH 8.61 coupled to a methine hy-
drogen at δH 5.13 (δC 53.42) which in turn revealed cou-
pling to a methyne carbinolic hydrogen at δH 4.38 (δC
77.32) and to a diastereotopic methylene group observed
at δH 4.45 and 4.53 (δC 62.36). On the other hand, in the
HMBC spectrum, the hydrogen resonance at δH 4.38
showed correlation to the δC 53.42 (CH), 62.38 (CH2),
73.26 (CH) and 34.55 (CH2). The HMQC spectrum es-
tablished the association of the methyne carbon at δC
73.26 with the carbinolic hydrogen at δH 4.32. This
analysis, based on amide function (RCONHR’), allowed
to establish the partial structure IV.
R - C - NH - CH - CH - CH - CH2 -
O
CH2OH
OH OH
IV
- CH2 - CH2- CH - C - NH - CH - CH - CH - CH2 -
O
CH2OH
OH OH
OH
V
The third oxygenate methine carbon at δC 72.75 was
associated to hydrogen in δH 4.64 by HMQC experiment.
In addition, the HMBC spectrum showed that this hy-
drogen was correlated with carbonyl carbon and with the
methylene carbons at δC 36.17 and 26.19, beta and gama
carbons, respectively, to carbonyl function. Thus, a par-
tial structure IV was expanded to V. Based on the above
spectral analysis and by comparison with spectral data
[IR, NMR (1H and 13C) and MS] of the literature [3,6-8]
the sample was identified as a ceramides mixture with
general structure VI.
N
O
OH
OH OH
OH
H
m
n
H
VI
The position of the double bond at C-19 was indicated
by strong peaks corresponding to m/z 97
(+CH2CHCHCH2CH2CH2CH3), 57 (+CH2CH2CH2CH3)
and 43 (+CH2CH2CH3). The E stereochemistry of double
bond was determined on the basis of 13C NMR chemical
shift of the methylene carbons adjacent to the olefinic
carbons, which is observed at δC ≈ 27.00 in Z isomers
and at δC ≈ 32.00 in E isomers [3,6].
After comparison with analogous compounds [3,7-11]
the relative stereochemistry inferred for the sterocenters
2, 3, 4 and 2’ was presumed to be S*, S*, R* and R*, re-
spectively. On the basis of the above mentioned data, the
structures of compounds 6 and 7 were established as
rel-(2S,3S,4R,19E)-2-[(2’R)-2’-hydroxydo cosanoylamin
o]-tetracosadec-19-ene-1,3,4-triol (6) and rel-(2S,3S,4R,
19E)-2-[(2’R)-2’-hydroxyhenicosanoylamino]-tetracosad
ec-19-ene-1,3,4-triol (7).
These data support the structures 6 and 7 proposed for
ceramides:
2´
1
23419
20
21
22
23
24
1´N
OH
O
OH
OH
OH
H
nm
n+1
n+2
5
618
3´
4´
n+3
H
6 [M-H]- 736.5277 n = 15, m = 11
7 [M-H]- 722.3396 n = 14, m = 11
The structures of acyl chains were confirmed by
analysis of the mixture of products (8 and 9) resulting
from methanolysis of 6 and 7. The CG-MS of 8 and 9
was in agreement with structures of 6 and 7, showing the
presence of two constituents, which were identified as
methyl-2-hydroxydocosanoato (m/z 370 [M+]) and methyl-
2-hydroxyhenicosanoato (m/z 356 [M+]).
COCH3
OH
O
n
8 M+ 370 n = 16
9 M+ 356 n = 15
The AcOEt fraction of the EtOH extract of the stems
of L. operculata was successively chromatographed on
silica gel column to afford 10 as white powder, mp
262˚C - 263˚C. The 13C NMR spectrum of 10 exhibited
thirty signals divided by DEPT spectra in nine quarter-
nary carbons, three CH, eleven CH2 and seven CH3

C. R. de S. FEITOSA ET AL.993
Table 2. 13C (125 MHz) and 1H (500 MHz) data of com-
pounds 6 and 7 in pyridin-d5, δ in ppm, J in Hz and multi-
plicities, in parenthesi s.
No. 6 and 7
C δC δH 2,3 JCH
1’ 175.64 - NH-1’
CH
2 53.42 5.13 (m) NH-1’; H-1; H-3
3 77.32 4.38 (m) H-1; H-2; H-5
4 73.26 4.32 (m) H-3; H-5
19 131.16 5.53 (m) -
20 131.04 5.53 (m) -
2’ 72.75 4.64 (m) -
CH2
1 62.36 4.45; 4.53 (m) H-2; H-3
5 34.55 1.95; 2.30 (m) H-3
6 27.00 1.71; 1.80 (m) H-5
7 - 17 30.25 - 30.53 1.27 - 1.33 (m) -
18 33.31 2.05 H-19; H-20
21 34.23 2.00; 2.30 (m) -
22 32.43 1.27 - 1.33 (m) -
23 23.28 1.27 - 1.33 (m) H-24
3’ 36.17 2.05; 2.25 H-2’
4’ 26.19 1.71; 1.80 H-2’
5’-n 30.25 - 30.53 1.27 - 1.33 (m) -
n + 1 32.43 1.27 - 1.33 (m) -
n + 2 23.28 1.27 - 1.33 (m) -
CH3
n + 3 14.55 0.89 (t, 6.4) -
24 14.55 0.89 (t, 6.4) -
groups. In the 1H and 13C NMR spectra of 10 characteris-
tic feature can be identified: methyl groups (δH 0.99, 1.04,
1.05, 1.08, 1.22, 1.28 and 1.42; δC 20.43, 16.82, 22.69,
31.44, 28.93, 18.28 and 33.64) all bonded to the quarter-
nary carbons; one carbinolic methyne carbon (δH 3.38,
dd, J = 10.0 and 5.0; δC 78.34); one tetrasubstituted dou-
ble bond (δC 134.89 and 134.45) and one carboxylic
carbon (δC 181.68). Together, these data were consistent
with a molecular formula of C30H48O3, including one
-OH and one -CO2H groups. Based on this NMR data
(Table 3), the seven degrees of unsaturation could be
attributed to one carbon-carbon double bond, one car-
bonyl group, and five ring systems. Compound 10 was
distinct from oleanolic acid by two remarks: the double
bond was located at ∆8 based on the long range connec-
tivities between two methyl signals at δH 0.99 (3H-25)
and 1.05 (3H-26) and the olefinic carbon signals at δC
134.89 (C-8) and 134.45 (C-9), respectively; the long
range coupling between the methyl signal at δH 1.42
(3H-30) and carbon carboxylic signal at δC 181.68 (C-29).
Thus, based on the above spectral analysis and by com-
parison with spectral data [IR, NMR (1H and 13C) of lit-
erature [12,13] the structure was confirmed as 3β-hy-
droxy-D:C-friedoolean-8-en-29-oic acid, known as bry-
onolic acid, a triterpenoid rare in nature.
HO
COOH
H
1
2
3456
7
8
9
10
11
12
13
14
15 16
17
18
19 20 21
22
23 24
25
26
27
28
29
30
The steroids were identified as 24α-etil-5α-colest-
7,trans-22-di en-3β-ol [11 (spinasterol)] and a mixture of
24α-ethyl-5α-colest-7,trans-22-dien-3β-ol (11) and 24β-
ethyl-5α-colest-7,trans-22,25-trien-3β-ol (12) from their
spectral analysis and by comparison of their physical and
spectral data with literature [14,15] values.
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
HO
R
H
27
20
21 22
23 24 25
26
28
29
H
R =
29
28
20
21 22
23 24 25
26
27
R =
H
+
29
20
21 22
23 24 25
26
27
28
H
R = 11
12

C. R. de S. FEITOSA ET AL. 994
Table 3. 13C (125 MHz) and 1H (500 MHz) data of com-
pound 10 in pyridin-d5, δ in ppm, J in Hz and multiplicities,
in parenthesis.
No.
C δC δH 2,3JCH
4 39.71 - 3H-23; 3H-24
8 134.89 - 3H-26
9 134.45 - 3H-25
10 38.12 - 3H-25
13 37.99 3H-27; 3H-26
14 42.44 - 3H-26; 3H-27
17 31.60 - H-19a
20 40.91 - H-19a; 3H-30
29 181.68 - H-19a; H-19b; 3H-30
CH -
3 78.34 3.38 (dd, 10.0; 5.0) 3H-23; 3H-24; 3H-25
5 51.25 1.08 3H-23; 3H-24; 3H-25
18 45.46 1.57 3H-28
CH2 3H-25
1 35.82 1.63; 1.84 -
2 28.27 1.84; 2.11 -
6 19.91 1.42; 1.72 -
7 28.97 1.86; 2.59 -
11 21.37 1.90; 1.94 -
12 30.82 1.22; 1.49 3H-27
15 25.77 1.37; 1.72 -
16 37.81 1.39; 2.75 3H-28
19 31.74 1.70; 2.73 -
21 30.98 1.46; 1.84 3H-30
22 35.37 1.03; 2.45 3H-28
CH3
23 28.93 1.22 (s) H-3; 3H-23
24 16.82 1.04 (s) -
25 20.43 0.99 (s) -
26 22.69 1.05 (s) -
27 18.28 1.28 (s) -
28 31.44 1.08 (s) -
30 33.64 1.42 (s)
Table 4. Cholinesterase inhibition of constituents from L.
operculata.
Substancea Zone of inhibition (mm)
6 and 7 12
11 Nb
12 8
Physostigminea,c 9
aConcentration = 2mg/mL; bN = No effect; cPositive control.
In the anticholine esterase activity test, fisostgmine
was used as positive control (with an inhibition zone of 9
mm) since it is a drug that binds and activates the ace-
tylcholine receptor. Acetylcholine esterase (AChE) hy-
drolyzes the neurotransmitter acetylcholine at one of the
highest known wnzymatic rates. Therefore the anticho-
line esterase activity of the ceramides (6 and 7) (with
aninhibition zone of 12 mm) is relevant as the results
below (Table 4).
4. Conclusions
Many previous studies showed that Luffa operculata is
rich in triterpenes cucurbitano type, as expected for a
Cucurbitaceae. Although almost all of these metabolites
were found only in their fruits, this study showed that the
stems and bark of the fruits of this plant are bioproduc-
tors of ceramides as well as steroids and triterpenes of
another type (oleanane). According to the analysis of
spectral data, the mixture of long chain ceramides seems
to involve more than two components, requiring a further
thorough study about the subject.
5. Acknowledgements
The authors are grateful to Fundação Cearense de
Amparo à Pesquisa do Estado do Ceará (FUNCAP) for
grants and to Conselho Nacional do Desenvolvimento
Científico e Tecnológico (CNPq-Brazil) for a research
fellowship and grants.
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