Jalapinoside II, a bisdesmoside resin glycoside, and related glycosidic acids from the officinal jalap root (Ipomoea purga)

Article abstract of DOI:10.1016/j.phytol.2016.07.022

Jalapinoside II, a macrocyclic bidesmoside resin glycoside with purgic acid C as its oligosaccharide core, was isolated by recycle preparative-scale HPLC from the MeOH-soluble extract of Ipomoea purga (Convolvulaceae), the officinal jalap root (“Rhizoma Jalapae”). This study also reports the complete NMR data assignment for purgic acid C and the structural elucidation of purgic acid D, both glycosidic acids were isolated, in conjunction with previously known purgic acids A and B, under saponification of the MeOH-soluble resin glycosides. HPLC and ¹³C NMR profiles were used as analytical tools for the authentication of the commercialized Mexican scammony resin. Reversal factor of multidrug resistance by the non-cytotoxic jalapinoside II was evaluated in vinblastine-resistant human breast carcinoma cells (RF_MCF-7/Vin+ > 1906).

Full text of DOI:10.1016/j.phytol.2016.07.022

Phytochemistry Letters 17 (2016) 85–93
Contents lists available at ScienceDirect
Phytochemistry Letters
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Jalapinoside II, a bisdesmoside resin glycoside, and related glycosidic
acids from the officinal jalap root (Ipomoea purga)
*
Elihú Bautista, Mabel Fragoso-Serrano, Rogelio Pereda-Miranda
Departamento de Farmacia, Facultad de Química, Universidad Nacional Autónoma de México, Mexico City 04510, Mexico
A R T I C L E I N F O
A B S T R A C T
Article history:
Jalapinoside II, a macrocyclic bidesmoside resin glycoside with purgic acid C as its oligosaccharide core,
was isolated by recycle preparative-scale HPLC from the MeOH-soluble extract of Ipomoea purga
(Convolvulaceae), the officinal jalap root (“Rhizoma Jalapae”). This study also reports the complete NMR
data assignment for purgic acid C and the structural elucidation of purgic acid D, both glycosidic acids
were isolated, in conjunction with previously known purgic acids A and B, under saponification of the
MeOH-soluble resin glycosides. HPLC and 13C NMR profiles were used as analytical tools for the
authentication of the commercialized Mexican scammony resin. Reversal factor of multidrug resistance
by the non-cytotoxic jalapinoside II was evaluated in vinblastine-resistant human breast carcinoma cells
(RFMCF-7/Vin+ > 1906).
Received 3 May 2016
Received in revised form 2 July 2016
Accepted 6 July 2016
Available online xxx
Keywords:
Ipomoea purga
Convolvulaceae
Bidesmoside
Resin glycosides
Oligosaccharides
Chemosensitizer
ã 2016 Phytochemical Society of Europe. Published by Elsevier Ltd. All rights reserved.
1. Introduction
Ipomoea genus were described as sources of resin glycosides which
functioned as modulators of efflux pumps that produce the
Historically, plant natural products have contributed to provide
highly polyfunctionalized biologically active compounds or
structural scaffolds for the development of anticancer drugs such
as podophyllotoxin, taxol, and vinblastine (Cragg et al., 2014).
However, the gradual loss of hypersensitivity by malignant cells to
anticancer drugs has derived in multidrug resistance (MDR), which
is one of the main causes limiting the success of cancer
chemotherapy. An increasing number of mechanisms of multidrug
resistance in cancer cells have been described. Nevertheless, the
most commonly found is the efflux of a broad range of cytotoxic
compounds mediated by ATP-binding cassette (ABC) transporters
(Szakács et al., 2014), such as P-glycoprotein (MDR protein1/P-gp,
ABCB1) and the breast cancer resistance protein (BCRP/ABCG2),
which have the task of detoxifying cells by detecting and expelling
hydrophobic toxins of innumerable structural types, including
anticancer drug (Roundhill et al., 2015).
multidrug-resistant phenotype in Gram-positive (Pereda-Miranda
et al., 2006b) and Gram-negative bacteria (Corona-Castañeda and
Pereda-Miranda, 2012), as well as in mammalian cancer cells
(Bautista et al., 2015; Castañeda-Gómez et al., 2013; Cruz-Morales
et al., 2012; Figueroa-González et al., 2012). These glycolipids
significantly lowered the efflux rate of rhodamine 123,
a
fluorescent efflux pump substrate, used to determine its accumu-
lation in efflux assays with MDR MCF-7/Vin cells. Immunofluores-
cence flow cytometry was used to detect the decreased expression
of P-gp by resin glycosides after incubation of MDR MCF-7/Vin cells
with an anti-P-gp monoclonal antibody (Figueroa-González et al.,
2012). Two examples of these potent MDR modulatory glycolipids
are purgin II and jalapinoside I (1) from I. purga. Reversal fold
(RFMCF-7/Vin >1906) indicated that both natural products are
extremely potent as vinblastine chemosensitizer at 25 mg/mL in
modulation assays (Castañeda-Gómez et al., 2013; Bautista et al.,
2015).
For these reasons, our efforts have been oriented to investigate
the chemical diversity of this class of MDR reversal agents from the
convolvulin fraction (ether insoluble or methanol-soluble resin
glycosides) of I. purga. In addition to its use as a purgative, this
member of the Mexican jalap root complex has been employed as
an anthelmintic and galactogogue, as well as in the treatment of
tumors. A 2 cm section of root boiled in a liter of water produces a
Resin glycosides are complex mixtures of glycolipids present in
some members of the morning glory family (Convolvulaceae),
many of which belong to the genera Ipomoea, Merremia, and
Operculina (Pereda-Miranda et al., 2010). Recently, members of the
* Corresponding author.
E-mail addresses: pereda@unam.mx, pereda@gmail.com (R. Pereda-Miranda).
http://dx.doi.org/10.1016/j.phytol.2016.07.022
1874-3900/ã 2016 Phytochemical Society of Europe. Published by Elsevier Ltd. All rights reserved.

86
E. Bautista et al. / Phytochemistry Letters 17 (2016) 85–93
Fig. 1. Chemical structures of jalapinosides I (1) and II (2).
decoction, a cup of which is taken cold before bedtime (Pereda-
Miranda et al., 2006a). In this work, we describe the isolation,
structural elucidation, and the modulatory activity of multidrug-
resistance in MCF-7 cancer cells of jalapinoside II (2), a novel
bidesmoside resin glycoside from the MeOH-soluble extract
prepared with the roots of I. purga. Also, it is described the
complete NMR data assignment for purgic acid C (3) as well as the
structural elucidation of a new glycosidic acid, named purgic acid D
(4). These glycosidic acids were used to generate HPLC and 13C
NMR profiles both used as analytical tools for authentication of the
commercialized Mexican scammony resin.
et al., 2006a). Two additional peracetylated peaks (tR values of 14.2
and 40.5 min) were subsequently saponificated and identified as
new glycosidic acids on the basis of their MS and NMR data, and
named as purgic acids C (3) and D (4) (Fig. 2). These glycosidic acids
OH
O
R2
2. Results and discussion
R1O
From the soluble MeOH extract of I. purga, a bidesmoside resin
glycoside, which was named as jalapinoside II (2, Fig. 1), was
isolated by recycling preparative-scale HPLC. This compound
represents the second intact bidesmosidic macrolactone resin
glycoside isolated from the convolvulin fraction of the jalap root. It
is important to emphasize the difficulties associated with the
isolation and purification of intact highly polar resin glycosides,
since all previous work on the chemical constituents of methanol-
soluble extracts from members of the morning glory family have
been limited to the isolation of their glycosidic acids after chemical
degradation (Ono et al., 1990; 2010).
The saponification of the soluble MeOH crude extract yielded
two fractions: a non-polar portion extracted with CHCl3 and an
H2O-soluble fraction; the non-polar CHCl3-soluble fraction was
analyzed by GC–MS to allow the identification of acetic, (2S)-2-
methyl-butanoic, (2S,3S)-3-hydroxy-2-methylbutanoic (nilic), and
dodecanoic acids, as the acylating residues; the H2O-soluble
fraction was partitioned with n-BuOH, further peracetylated, and
subsequently analyzed by recycling HPLC (Pereda-Miranda and
Hernández-Carlos, 2002), allowing the isolation of four peaks. The
first two peaks (tR 7.8 and 11.5 min) were identified as the
peracetates of purgic acids A (5a) and B (6a) (Fig. 2) through the
comparison of their 1D NMR data, HPLC retention time, and
melting points with those previously described (Pereda-Miranda
R1O
R1O
O
O
R1O
O
O
R1O
O
O
H3C
O
OR1
R1O
R1O
O
O
O
R1O
R1O
R1O
O
OR1
O
R1O
OR1
OR1
Qui :
O
3 R1 = H, R2 = OQui, n = 2
4 R1 = H, R2 = OQui, n = 4
5 R1 = R2 = H, n = 2
R1O
OR1
OR1
5a
R1 = Ac R2 = H, n = 2
6 R1 = R2 = H, n = 4
6a R1 = Ac R2 = H, n = 4
Fig. 2. Structure of purgic acids A-D.

E. Bautista et al. / Phytochemistry Letters 17 (2016) 85–93
87
possess the same glycosylation sequence in the oligosaccharide
core as purgic acids A (5) and B (6) (Fig. 2); although both differing
from each other in their aglycone: ipurolic acid, (3S,11S)-
dihydroxytetradecanoic acid (Ono et al., 2010) in purgic acid C
(3), and ipolearic acid, (3S,11S)-dihydroxyhexadecanoic acid (Ono
et al., 1990) in purgic acid D (4). In addition, they presented a
quinovose unit linked at the hydroxyl group at C-3 of the aglycone
(Fig. 2) as do most of the glycosidic acids isolated from ether-
insoluble resin glycosides (Ono et al., 1990; 2010).
each one were assigned by the correlations showed in the COSY
spectrum, starting from the anomeric signal for each system: dH
4.71, d, J = 7.6 Hz, Qui-1; 5.64, d, J = 7.6 Hz; Glc-1; 6.28, br s, Rha-1;
6.01, d, J = 7.8 Hz, Glc0-1; 5.20, d, J = 7.6 Hz, Qui0-1; 5.62, d, J = 7.5 Hz,
Fuc-1; 4.75, d, J = 7.6 Hz, Qui00-1. In the 13C NMR spectrum, the same
number of anomeric signals was observed at dC 102.7 (Qui-1),102.8
(Glc-1), 101.0 (Rha-1), 101.6 (Glc0-1), 105.0 (Qui0-1), 103.6 (Fuc-1),
and 104.0 (Qui00-1). The HSQC and HMBC experiments allowed the
assignments of the additional 13C NMR signals. The glycosylation
pattern of 3 was established as the same for purgic acids A (5) and B
(6) on the basis of the observed following HMBC 3JCH cross peaks:
H-1 (4.71, Qui-1) with C-11 (78.8, Ipur-11); H-1 (5.64, Glc-1) with
C-2 (80.1, Qui-2); H-1 (6.28, Rha-1) with C-2 (74.8, Glc-2); H-3
(5.16, Rha-3) with C-1 (101.6, Glc0-1); H-2 (4.07-3.97, Glc0-2) with
C-1 (105.0, Qui0-1); and from H-1 (5.62, Fuc-1) with C-4 (79.3, Rha-
4). Additionally, the HMBC cross peak of H-1 (4.75, Qui00-1) with C-
3 (63.8, Ipur-3) confirmed the position for the bidesmosidic
portion.
These structural features for compound 3 were supported by its
acid hydrolysis products which included ipurolic acid and the
following monosacharides:
D-quinovose, D-glucose, D-fucose, and
L-ramnose in a ratio of 3:2:1:1 (Bautista et al., 2015). In addition,
the ESIMS data for 3 gave quasi-molecular ions at m/z 1313 [MꢀH]ꢀ
and 1337 [M+Na]+ as well as readily detectable negative ions by
FABMS resulting from glycosidic cleavage of the sugar moieties at
m/z 1167 [1313–146]ꢀ, 1021 [1167–146]ꢀ, 859 [1021–162]ꢀ, 713
[859–146]ꢀ, 567 [713–146]ꢀ, and 405 [567–162]ꢀ. All of these ions
are consistent with previously described spectra (Bautista et al.,
2015). The micro-scale saponification originally performed with
jalapinoside I (1) afforded purgic acid C (3) in a very small quantity
to complete its spectroscopic characterization by NMR (Bautista
et al., 2015). Thus, the scale-up of this reaction allowed the
purification of a sufficient amount of compound 3 to complete the
analysis of its 1D and 2D NMR spectra (Tables 1 and 2). Seven spin
systems were observed in the TOCSY experiment. The signals for
Acid hydrolysis of 4 afforded ipolearic acid as well as
D-
quinovose, -glucose, -fucose, and -ramnose in a ratio of 3:2:1:1.
D
D
L
The ESIMS/MS data in the positive mode for purgic acid D (4),
showed the quasi-molecular ion at m/z 1343 [M+H]+. The following
ion peaks resulted from the glycosidic cleavage common to
bidesmosidic MeOH-soluble resin glycosides (Bautista et al., 2015;
Ono et al., 2010): 1197 [M + H ꢀ 146 (methylpentose unit)]+, 1051
[1197–146]+, 889 (1051–162 (hexose unit)]+, 743 [889–146]+, 597
Table 1
1H (400 MHz) NMR Data of Purgic acids C (3) and D (4), as well as their Peracetates (3a and 4a) in Piridine-d5
(d in ppm, J in Hertz).
position
3
3a
4
4a
position
3
3a
4
4a
Qui-1
2
3
4.71 d (7.6)
4.17–4.10a
4.43 dd (8.4,
8.3)
4.87 d (7.9)
4.77 d (7.6)
4.86 d (7.9)
Qui'-1
2
3
5.20 d (7.6)
4.08–4.01a
4.03–3.97a
5.16 d (7.6)
5.62–5.55a
5.62–5.55a
5.10 d (7.6)
4.08–4.01a
4.03–3.97a
5.16 d (8.0)a
5.72–5.63a
5.62–5.55a
5.42 dd (8.9, 7.9) 4.16 dd (8.6, 7.6)a 5.42 dd (8.6, 7.9)
5.72–5.66a
4.63 dd (8.9, 8.6) 5.72–5.66a
4
5
3.45 dd (9.0,
8.4)
5.19 dd (9.4,
9.2)a
3.53 dd (9.0, 8.9) 5.17 dd (9.6,
9.1)a
4
5
3.63 dd (9.0,
8.8)
5.38 dd (9.4,8.9) 3.63 dd (9.0, 8.8) 5.37 dd (9.6,
9.0)
3.71–3.62a
3.98 dq (9.4, 5.8) 3.71–3.62a
4.00 dq (9.6, 6.0)
3.78–3.73a
3.73 ma
3.77 dd (8.8,
3.76 ma
5.9)a
6
1.45 d (6.0)
5.64 d (7.6)
4.29–4.22a
1.46 d (5.7)a
4.75 d (7.5)
4.22 dd (7.8,
7.5)a
1.45 d (6.0)
5.74 d (7.6)
1.46 d (6.0)a
4.75d (7.3)
6
1.64 d (5.4)
5.62 d (7.5)
4.15–4.05a
147 d (5.7)a
5.62 d (7.2)
5.73 dd (10.0,
8.3)
1.64 d (5.9)
5.79 d (7.5)
4.34 dd (9.3,
7.5)a
1.48 d (6.0)a
5.62 d (7.5)
5.84 dd (9.8,
7.6)
Glc-1
2
Fuc-1
2
4.28 dd (9.6, 7.6)a 4.26 dd (8.1,
7.3)a
3
4.21–4.10a
5.62 dd (9.0,
4.19–4.12a
5.63 dd (9.0,
3
4.10–4.04a
5.65–5.53a
4.35–4.24a
5.68–5.62a
7.8)a
7.9)a
4
5
6a
4.07–4.01a
3.81–3.75a
5.10 dd (9.4, 9.0) 4.07–4.01a
5.13 dd (9.5, 9.0)
4.25–4.15a
4.60–4.55
4
5
6
4.05–3.97a
3.76–3.72a
1.59 d (6.3)
5.75–5.70a
4.30–4.15a
1.34 d (5.9)
4.05–3.97a
3.76–3.72a
1.53 d (6.3)
5.75–5.70a
4.30–4.15a
1.34 d (6.0)
4.25–4.18a
3.81–3.75a
4.43 dd (10.5,
3.0)
4.37 dd (9.1, 3.0) 4.60–4.55a
6b
Rha-1
2
4.36–4.29a
6.28 br s
4.86 dd (3.0,
1.5)a
4.25–4.21a
5.50 br sa
5.70–5.65a
4.36–4.29a
6.45 br s
4.28–4.23a
Qui”-1
2
3
4.75 d (7.6)
4.01–3.89a
4.20–4.09a
5.26 d (8.2)
5.57–5.48a
5.68 dd (9.0,
8.8)a
4.83 d (7.6)
4.05–3.97a
4.20–4.13a
5.27 d (8.1)
5.56–5.45a
5.68 dd (9.6,
9.0)
5.52 dd (9.4,
9.0)
5.51 br sa
4.85 dd (3.0, 1.5)a 5.70–5.65a
5.31 dd (9.1, 3.0) 4.66–4.60a
3
4
5
5.16 dd (9.1, 3.0) 4.70–4.50a
4
5
6
3.66–3.62a
3.73–3.68a
1.47 d (6.2)
5.52 dd (9.4,
3.80–3.72a
8.8)a
4.86–4.76a
4.30–4.21a
4.55–4.45a
4.80–4.76a
4.33–4.25a
3.87 dq (9.4, 5.7) 3.83–3.78a
3.84 dq (9.4,
5.9)
5.06 dd (9.0,
6.0)
5.20 dd (9.0, 6.1) 4.60–4.50a
1.29 d (5.7)
1.67 d (6.2)
1.29 d (5.9)
6
1.83 d (6.0)
6.01 d (7.8)
4.07–3.97a
4.56–4.48a
4.08–4.02a
1.88 d (6.4)
5.49 d (7.3)a
4.25–4.19a
5.64–5.57a
5.30 dd (10.4,
9.4)
1.95 d (6.1)
6.25 d (7.8)
4.07–3.97a
4.56–4.48a
4.08–4.02a
1.87 d (6.0)
5.49 d (7.5)a
4.32–4.28a
5.68–5.60a
5.30 dd (10.6,
9.5)
Ipurꢀ1 or Ipolꢀ1b
Glc'-1
2a
2b
3
2.57–2.51a
2.51–2.46a
4.30–4.25a
3.85 m
2.62–2.56a
2.56–2.50a
4.35–4.30a
3.70 ma
2.55–2.51a
2.50–2.46a
4.30–4.25a
3.91 m
2.65–2.57a
2.57–2.51a
4.35–4.30a
3.74 ma
2
3
4
11
5
6a
4.20–4.13a
4.47–4.41a
4.34–4.28a
4.58–4.52a
4.20–4.13a
4.55 dd (11.5,
5.6)a
4.36–4.27a
4.60–4.53a
14 or 16 0.90 t (7.1)
0.89 t (6.6)
0.95 t (7.1)a
0.90 t (7.0)
6b
4.20–4.14a
4.39–4.30a
4.20–4.14a
4.36–4.30
a
Overlaped signa.
Ipur: Ipurolic acid; Ipor: Ipolearic acid.
b

88
E. Bautista et al. / Phytochemistry Letters 17 (2016) 85–93
Table 2
13C (100 MHz) NMR Data of Purgic acids C (3) and D (4), as well as their Peracetates (3a and 4a) in Piridine-d5
(d
in ppm).
position
3
3a
4
4a
position
3
3a
4
4a
Qui-1
2
3
4
5
6
Glc-1
2
3
4
5
6
Rha-1
2
3
4
5
6
102.7
80.1
78.5
76.6
70.5
18.3
102.8
74.8
77.4
71.0
77.6
62.2
101.0
71.5
78.7
79.3
67.9
18.9
101.6
83.7
76.8
72.7
77.8
63.1
100.8
75.9
75.8
74.3
69.7
18.0
101.2
72.8
76.0
69.8
72.6
63.3
97.7
73.6
78.5
76.9
67.7
19.0
102.8
78.4
75.9
70.0
69.6
62.6
102.5
80.9
78.8
77.1
72.9
18.4
102.6
78.1
73.8
72.9
77.1
62.0
100.4
71.9
78.1
79.3
68.0
19.0
100.9
84.9
76.8
72.7
78.2
63.1
100.4
72.8
76.0
74.3
69.9
17.5
Qui'-1
2
3
4
5
6
Fuc-1
2
3
4
5
6
105.0
77.4
77.7
76.7
77.6
18.5
103.6
73.1
75.7
71.0
71.2
18.8
104.0
75.8
78.9
72.2
77.3
16.9
180.7
38.0
63.8
78.8
14.2
101.6
72.6
73.5
72.9
70.3
17.9
105.2
77.4
77.7
76.9
77.2
18.8
103.2
73.6
74.9
72.8
71.2
17.1
103.7
75.8
78.4
73.9
77.3
18.7
176.6
34.8
63.6
78.6
14.4
101.3
72.6
73.6
72.8
69.9
17.9
101.8
72.7
75.9
69.8
72.6
63.4
97.3
73.7
78.5
77.0
67.6
19.0
102.4
78.3
75.9
69.8
69.5
62.4
101.4
69.4
73.9
71.2
69.5
16.4
102.0
72.1
75.9
76.2
71.2
18.2
176.8
35.6
63.0
80.5
14.7
101.0
69.6
73.9
71.2
69.3
16.4
101.6
72.1
75.7
76.2
70.1
18.2
176.2
34.9
62.8
80.0
14.3
Qui”-1
2
3
4
5
6
Glc'-1
Ipurꢀ1 or Ipolꢀ1a
2
3
4
5
6
2
3
11
14 or 16
a
Ipur: Ipurolic acid; Ipor: Ipolearic acid.
Fig. 3. Positive ESIMS fragmentation of compound 4.
[1197–146–162–146–146]+, 435 [597–162]+, and 289 [435–146]+
(Fig. 3). The difference of 28 mass units between compounds 3 and
4 as well as the production of the same general fragmentation
pattern established that both glycosidic acids differed in the chain
length of their aglycone and indicated the presence of ipolearic
acid, (3S,11S)-dihydroxyhexadecanoic acid, in purgic acid D (4).
Fig. 3 illustrates the fragmentation pattern in positive mode ESIMS
for compound 4. The 1D and 2D NMR data of compound 4
(Tables 1 and 2) were equivalent to purgic acid C (3) since both
have the same oligosacharide core. Thus, the signals assignment
for 4 was accompanied by comparison with the NMR data of
compound 3.
It has been reported that these saponification products are
distinctive enough for HPLC and NMR differentiation of I. purga
from other members of the Mexican jalap root complex (Pereda-
Miranda et al., 2006b). Thus, these profiles were used as analytical
tools for the authentication of the commercialized Mexican
scammony resin, which is used as a purgative remedy, sold in
Mexico and exported worldwide by Mixim Laboratories, manu-
factures of botanical extracts.
prepared with this resin, after sonication with H2O. Then, it was
submitted to saponification. The dried neutral aqueous phase from
A MeOH-soluble extract was
Fig. 4. Expansion at 100–110 ppm of 13C NMR spectra of glycosidic acids A-D
liberated by saponification of crude MeOH-soluble extracts from Ipomoea purga
(“Rhizoma Jalapae”).

E. Bautista et al. / Phytochemistry Letters 17 (2016) 85–93
89
and 101.1; and not the purgic acids (Pereda-Miranda and
Hernández-Carlos, 2002; Pereda-Miranda et al., 2006a).
Jalapinoside II (2) was isolated as a colorless solid. Its HRESIMS
showed the quase-molecular ion peak at m/z 1705.8402 [M + H]+
indicating a molecular formula C80H137O38 (calcd 1705.8782). The
analysis by HPLC-ESIMS/MS showed the presence of ion peaks
produced through the glycosidic cleavage (Pereda-Miranda et al.,
2006a) and the elimination of acylation residues (Cruz-Morales
et al., 2012; Castañeda-Gómez et al., 2013) at m/z 1559 [M + H ꢀ 146
(methylpentose unit)]+, 1459 [M + H ꢀ 146–100 (nylic acid)]+, 1297
[1459–162 (hexose unit)]+, and 739 [1297–146–182–146–84]+
(Fig. 5). Jalapinosides I (1) and II (2) presented a common ion peak
at m/z 1459 which was generated by the loss of a fragment of 246
uma [146–100 (nylic acid)]+ in compound 2 and of 230 uma [146–
84 (methylbutiric acid)]+ in compound 1. This difference of 16 uma
indicated that compound 2 possess nylic acid as the acylating
residue at the terminal quinovose unit in constrast to 1 with a
residue of methylbutiric acid (Bautista et al., 2015; Hernández-
Carlos et al., 1999). In the 13C NMR spectrum, seven signals for
anomeric carbons were observed in the region comprised between
dC 95–110 ppm (Table 3). Each signal allowed the identification of
the respective anomeric protons through their correlations in the
HSQC spectrum, which established the spin systems of each
monosaccharide moieties. The observed cross peaks in the COSY
spectrum allowed completing the 1H NMR signal assignment. The
acylation positions as well as lactonization site were determined
by the observed HMBC correlations: H-3 (5.98, Glc-3) with C-1
(173.1, Ipur-1), H-6 (5.66 and 5.70, Glc-6) with C-1 (168.2, Ac-1), H-
2 (5.91, Rha-2) with C-1 (176.6, Mba-1), H-3 (5.38, Qui0-3) with C-1
(175.2, Nla-1), and H-3 (5.96, Fuc-3) with C-1 (173.8, Dodeca-1).
The preparation and identification of 4-bromophenyacyl deriva-
tives of (2S)-2-methylbutyric and (2R,3R)-3-hydroxy-2-
Fig. 5. Positive ESIMS fragmentation of compound 2.
this alkaline hydrolysis was acetylated and directly analyzed by
HPLC to afford the same four major peaks isolated from the
convolvulin fraction prepared with the crude drug. These
derivatives corresponded to peracetylated purgic acids A (5a, tR
7.8 min), B (6a, tR 11.5 min), C (3a, tR 14.2 min), and D (4a, tR
40.5 min) and were further submitted to an alkaline hydrolysis to
obtain the glycosidic acids for the acquisition of their 13C NMR
profiles (Fig. 4). Their anomeric signals are easily distinguishable
and used as a fingerprint for pattern recognition, as well as
structural dereplication (Bautista et al., 2015; Pereda-Miranda
et al., 2006a), and constitute a good starting point for structure
elucidation as described above for purgic acids C (3) and D (4). The
presence of these oligosaccharide cores suggests that the plant
material used by the manufactures of the commercial Mexican
scammony resin is the officinal jalap root and does not represent
the species I. orizabensis (Mexican scammony) since the glycosidic
core for this false jalap root should correspond to a tetrasaccharide,
scammonic acid A: 13C NMR anomeric signals
d 104.9, 102.1, 101.5,
Table 3
1H (700 MHz) and 13C (175 MHz) NMR Data of Compound 2 in Piridine-d5
(d
in ppm, J in Hertz).
position
position
dH
dC
dH
dC
Qui-1
2
3
4
5
6
Glc-1
2
3
4
5
6a
6b
Rha-1
4.90 d (7.6)
103.0
80.4
78.5
77.2
72.6
18.3
101.7
75.6
74.1
Fuc-1
2
3
4
5
6
Qui”-1
2
3
4
5
6
Ipur-1
2a
2b
3
11
14
Ac-1
2
Mba-1
2
2-Me
3-Me
Nla-1
2
5.78 d (7.8)
4.27ꢀ4.23a
5.96 d (7.8)
4.33ꢀ4.27a
3.68 m
1.66 d (6.0)
4.82 d (7.7)
4.05ꢀ3.99a
4.17 dd (8.8, 8.0)
4.50ꢀ4.47a
3.75 dd (9.1, 6.2)
1.44 d (6.2)
102.1
74.3
74.1
4.27ꢀ4.22a
4.79 dd (8.8, 7.6)
3.55 dd (9.9, 7.6)
3.92 dd (9.9, 6.2)a
1.55 d (6.2)
73.6
77.7
18.8
103.5
75.6
78.2
72.7
77.1
5.86 d (7.8)
4.23ꢀ4.27a
5.98 dd (7.7, 7.7)a
4.33ꢀ4.28a
69.4
63.1
74.4
4.42 dd (8.0, 5.5)
5.70 dd (10.3, 3.2)
5.66 dd (10.3,5.5)
6.46 d (1.8)
16.4
173.1
43.4
97.0
74.1
74.0
80.1
67.5
19.2
101.5
86.1
72.7
72.4
78.1
62.9
2.71 ddd (14.2, 8.8, 3.3)
2.73 ddd (14.2, 8.8, 3.3)
4.42ꢀ4.38a
2
3
4
5
5.91 dd (3.6, 1.8)
5.50 dd (9.2, 3.6)
4.61 dd (9.5, 9.2)
5.20 dd (9.5, 6.2)
1.96 d (6.2)
68.3
81.1
11.9
3.92ꢀ3.88a
1.01 t (7.4)
6
168.2
12.3
176.6
41.5
16.9
14.4
175.2
48.9
21.1
69.3
16.9
173.8
34.3
Glc'-1
2
3
4
5
6a
6b
Qui'-1
2
3
4
5
6
6.37 d (7.8)
2.04 s
3.99ꢀ4-04a
4.53 dd (9.0, 7.8)
3.85 dd (9.5, 9.0)
4.34 dd (9.5, 7.2)
4.55ꢀ4.49a
2.64 ddd (7.0, 6.8, 2.5)
1.22 d (7.0)
0.96 t (7.1)
4.05ꢀ3.98a
2.91 ddd (7.1, 7.1, 2.6)
1.35 t (7.0)
5.14 d (7.8)
107.1
75.9
76.7
76.4
77.1
18.4
2-Me
3
3-Me
Dodeca-1
2a
4.10ꢀ4.03a
4.38ꢀ4.30a
5.38 dd (9.5, 9.5)
4.27ꢀ4.22a
1.22 d (7.0)
3.75 dd (9.1, 6.2)
1.74 d (6.2)
2.35 dd (15.6, 7.0)
2.27 dd (15.6, 6.8)
2b
a
Overlaped signal.

90
E. Bautista et al. / Phytochemistry Letters 17 (2016) 85–93
methylbutyric acids from the saponification of the crude resin
glycosides was used to confirmed the absolute configuration for
these chiral esterifying residues (Castañeda-Gómez et al., 2013;
Cruz-Morales et al., 2012; Pereda-Miranda and Hernández-Carlos,
2002).
Compound 2 was tested for its cytotoxic activity against a panel
of human cancer cell lines: colon (HCT-15), cervix (HeLa), and
breast (MDA-MB-231, MCF-7sens, MCF-7/Vinꢀ and MCF-7/Vin+).
4. Experimental
4.1. General experimental procedures
Melting points (uncorrected) were determined on a Fisher-
Johns apparatus. Optical rotations were measured on a Perkin-
Elmer 341 polarimeter. 1H (700 MHz) and 13C (175 MHz) NMR
experiments were performed on a Bruker Avance III HD NMR
spectrometer. Chemical shifts were referenced toTMS, and J values
are given in Hz. ESIMS, HRESIMS and MALDI-TOFMS were recorded
on a Bruker Daltonics Esquire 6000, Thermo LTQ Orbitrap XL, and
Bruker MicrO-TOF-Q mass spectrometers, respectively. Waters
HPLC equipment was composed of a 600E multisolvent delivery
system with a refractive index detector (Waters 410). Control of
the equipment, data acquisition, and processing of the chro-
matographic information were performed by the Empower 2
software (Waters). HPLC-ESIMS was carried out on an Agilent 1200
Rapid Resolution Liquid Chromatograph coupled to a Bruker
Daltonics Esquire 6000 mass spectrometer. GC–MS was performed
on a Thermo-Electron instrument coupled to a Thermo-Electron
spectrometer. GC conditions: DB-5MS (5% phenyl)-methylpolysi-
No cytotoxicity was detected for all the cell lines (IC50 > 20 mg/mL).
Based on our previous results of resin glycoside drug uptake
inhibition with an anti-P-gp monoclonal antibody and rhodamine
123 (Figueroa-González et al., 2012), the capability of compound 2
to modulate the multidrug resistance in the MDR MCF-7/Vin cell
line was carried out. The modulation assay employed parental or
vinblastine-sensitive (MCF-7 sens) and vinblastine-resistant
(MCF-7/Vinꢀ and MCF-7/Vin+) human breast cancer cells (Table 4).
Reversal fold value for compound 2 (RFMCF-7/Vin+ > 1906) showed
that it was equipotent to jalapinoside I at a concentration of 25 mM
(1, Bautista and Pereda-Miranda, 2015). Comparison of these data
with those previously described for other convolvulaceous resin
glycosides showed that compounds 1 and 2, together with purgin II
(Castañeda-Gómez et al., 2013) and albinoside III (Cruz-Morales
et al., 2012), constitute the most potent glycolipid type chemo-
sensitizers in modulation assays (Bautista et al., 2015). There are no
clear evidences to establish structure-activity relationships since
minor variations in the acylation pattern of the oligosaccharide
cores could affect their MDR reversal activities (Corona-Castañeda
and Pereda-Miranda, 2012; Corona-Castañeda et al., 2016;
Figueroa-González et al., 2012). However, an essential structural
requirement for the MDR modulatory activity is the presence of the
macrolactone, since non-cyclic resin glycosides, as the glycosidic
acids, displayed marginal activity (Song et al., 2015).
loxane column (30 m ꢁ 0.25 mm, film thickness 0.18
mm); He,
linear velocity 30 cm/s; 2 mL/min; 50 ꢂC isothermal for 4 min,
linear gradient to 300 ꢂC at 40 ꢂC/min; final temperature hold,
20 min. MS conditions: ionization energy, 70 eV; ion source
temperature, 250 ꢂC; interface temperature, 270 ꢂC; scan speed,
2 scans sꢀ1; mass range, 45–600 amu.
4.2. Chemicals, cell lines, and cell cultures
Colon (HCT-15), cervix (HeLa), and breast (MCF-7 and MDA-MB-
231) carcinoma cell lines were obtained from the American Type
Culture Collection. The resistant MCF-7/Vin was developed
through continuous exposure to vinblastine during five consecu-
tive years as previously reported (Figueroa-González et al., 2012).
All cell lines were maintained in RPMI 1640 medium supple-
mented with 10% fetal bovine serum and were cultured at 37 ꢂC in
an atmosphere of 5% CO2 in air (100% humidity). To maintain drug
resistance, MCF-7/Vin+ cells were cultured in medium containing
3. Conclusions
Due to the morphological resemblance among the false jalap
roots, e.g., I. orizabensis and/or I. stans, with the officinal jalap
(I. purga), adulteration occurs due to the negligence of suppliers
and collectors. HPLC and 13C NMR profiles can be employed to
recognize the constant composition of the commercialized resins
prepared from the officinal jalap root. Resin glycosides are a group
of natural products with a high structural complexity that is
responsible for its chemical diversity. Their glycolipid nature
provides these amphipathic compounds with the ideal structural
features for poly-specific drug binding to MDR efflux pumps of
therapeutic interest. The results obtained for the vinblastine
resensitization in MCF-7 cancer cell line by jalapinoside II (2)
support the proposal for the development of potent chemo-
sensitizers based on resin glycosides for cancer chemotherapy.
0.192 mg/mL of vinblastine. At the same time, a stock of MCF-7/
Vinꢀ cells was maintained in vinblastine-free medium.
4.3. Plant material
The roots of I. purga (Wender) Hayne were collected in
Coxmatla, Municipio de Xico, Veracruz, Mexico, in November
2010 and identified by Botanist Alberto Linajes. Three voucher
specimens were deposited at the following herbaria: Instituto de
Ecología, Veracruz, México (XAL ID-365843); Departamento
Farmacia, Facultad de Química, UNAM (J. Castañeda and R. Pereda
RP-06); and the National Herbarium, Instituto de Biología,
Universidad Nacional Autónoma de México (MEXU 426765).
Table 4
Modulation of Vinblastine Cytotoxicity in Drug Sensitive MCF-7 and Multidrug Resistant MCF-7/Vin by Jalapinoside II (2).
IC50
(m
g/mL)
reversal foldc
compounda
MCF-7/Vinꢀ
MCF-7/Vin+
MCF-7 sens
RFMCF-7/Vin
RFMCF-7/Vin
RFMCF-7sens
ꢀ
+
vinblastine
1.02 ꢃ 0.18
<0.00064
0.037 ꢃ 0.01
1.22 ꢃ 0.14
<0.00064
0.31 ꢃ 0.19
0.047 ꢃ 0.01
<0.00064
0.003 ꢃ 0.001
Jalapinoside II (2)
>1593.8
27.6
>1906.3
3.9
73.4
15.7
reserpineb
a
Serial dilutions from 0.00064 to 10
m
g/mL of vinblastine in the presence or absence of glycolipid (25
g/mL as positive control.
RF = IC50 Vinblastine/IC50 Vinblastine in the presence of glycolipid. Each value represents the mean ꢃ SD from three independent experiments.
m
g/mL).
b
c
Reserpine = 5
m

E. Bautista et al. / Phytochemistry Letters 17 (2016) 85–93
91
4.4. Extraction and isolation
4.7. Acetylation of n-BuOH fraction
The powdered roots (3.8 kg) were extracted exhaustively by
maceration with MeOH to obtain a dried extract (202.8 g), which
was suspended (25 g) in deionized water (3 ꢁ100 mL) and
subjected to sonication for 30 min to afford H2O-soluble and
ꢀinsoluble fractions (9.4 and 13.3 g, respectively). The H2O-
insoluble fraction (12.0 g) was submitted to HPLC on a Symetry
The saponification H2O-soluble residue obtained from the n-
BuOH fraction (0.712 g) was dissolved in pyridine (13 mL) and
acetic anhydride (23 mL) was added by dropping. The resulting
mixture was stirred for 24 h at room temperature. Then, the
reaction mixture was worked up as usual to obtain a residue
(0.726 g). This residue was submitted to HPLC on a NH2 column
C
18 column (Waters, 7
of CH3CNꢀꢀH2O (3:1), a flow of 8.2 mL/min and a sample
concentration of 200 mg/mL, injecting 500 L each time. The
m
m, 19 ꢁ150 mm) with an isocratic elution
(YMC, 5
(3:1), a flow of 1.4 mL/min, and a sample concentration of 100 mg/
mL, injecting 200 L each time. The peaks with retention time of
m
m, 10 ꢁ150 mm) with an isocratic elution of CH3CN:H2O
m
m
peak with tR values of 5.3 min was collected by the techniques of
heart cutting and peak shaving, and purified by recycling over 8–10
times at the same column, using a flow of 4.1 mL/min to afford
compound 2 (5.3 mg).
7.8 min (5a, 106.1 mg), 11.5 min (6a, 52.1 mg), 14.2 min (3a,
179.7 mg), and 40.5 min (4a, 178.0 mg) were collected and further
submitted to recycling HPLC to achieve chromatographic homo-
geneity by using the above-mentioned instrumental conditions.
The peaks with retention time of 7.8 min and 11.5 min were
identified as the peracetates of purgic acids A (5) and B (6)
respectively, by comparison of their spectroscopic NMR and MS
data with values previously described (Pereda-Miranda et. al.,
2006). The peaks with retention time of 14.2 min and 40.5 min
corresponded to compounds 3a and 4a.
4.4.1. Jalapinoside II (2)
White powder: mp 180–182 ꢂC; [a 589
]
ꢀ51.4, [a 578 ꢀ55.7,
]
[
a]546
ꢀ61.4, [a 436
]
ꢀ95.7, [
a
]
365 ꢀ145.7 (c 0.07, MeOH); 1H and 13
C
NMR, see Table 1; positive MALDI-TOFMS m/z 1705 [M + H]+;
positive ESIMS/MS m/z 1705 [M + H]+, 1559 [M + H
ꢀ
146
(methylpentose unit)]+, 1459 [M + H ꢀ 146–100 (nylic acid)]+,
1297 [1459–162 (hexose unit)]+, and 739 [1297–146–182–146–
84]+; HRESIMS m/z 1705.8402 [M + H]+ (calcd for C80H136O38 + H+
requires 1705.8782);
4.7.1. Spectroscopic characterization of 3a
White powder: mp 92–95 ꢂC; [
a
]
589 ꢀ17.9, [a 578
]
ꢀ18.5, [
a]
546
ꢀ20.8, [a 436
]
ꢀ34.4, [a 365
]
ꢀ52.0 (c 12.6, MeOH); For 1H and 13C
NMR spectroscopic data, see Tables 1 and 2; MALDITOF m/z
4.5. Alkaline hydrolysis of the MeOH extract
2071.7985 [M + H]+ (calcd for C92H134O52 + H+ requires 2071.7914).
A solution containing 1 g of the MeOH extract in 30 mL of KOH
aqueous 5% was submitted to reflux at 95 ꢂC for 3 h. Then, the
mixture was acidified to pH 5.0 and extracted with CHCl3
(3 ꢁ 30 mL). This organic layer was washed with H2O, dried with
Na2SO4 and the solvent was removed under reduced pressure and
directly analyzed by GC–MS to displayed four peaks, identified as
acetic acid, m/z [M]+ 60 (65), 45 (80), 43 (100), 29 (19), 15 (25); 2-
methylbutanoic acid, m/z [M]+ 102 (2), 87 (25), 74 (100), 57 (64), 41
(30); 3-hydroxy-2-methylbutanoic acid, m/z [M]+ 118 (2), 115 (10),
101 (20), 84 (12), 73 (70), 60 (100); and dodecanoic acid, m/z [M]+
200 (16), 171 (9), 157 (22), 143 (5), 129 (34), 115 (18), 101 (12), 85
(28), 73 (100), 60 (95), 43 (62).
4.7.2. Spectroscopic characterization of 4a
White powder: mp 89–90 ꢂC; [a 589
]
ꢀ13.3, [a 578
]
ꢀ14.4, [
a]
546
ꢀ15.6, [
a
]
ꢀ26.7, [a 365
]
ꢀ40.0 (c 0.9, MeOH); For 1H and 13C
436
NMR spectroscopic data, see Tables 1 and 2; MALDITOF m/z
2099.8285 [M + H]+ (calcd for C94H138O52 + H+ requires 2099.8227).
4.8. Alkaline hydrolysis of compounds 3a and 4a
In a ball flask containing 150 mg of compound 3a were added
10 mL of a solution of 5% KOHꢀꢀH2O and the mixture was stirred
under reflux conditions at 95 ꢂC for 4 h. The mixture reaction was
acidified to pH 5.0 and extracted with EtOAc (3 ꢁ 30 mL). Then, it
was further extracted with n-BuOH and concentrated under
vacuum to obtain 80 mg of compound 3. The same procedure was
repeated with derivative 4a (130 mg) to obtain 65 mg of compound
4.
4.6. Preparation of 4-Bromophenyacyl derivatives of esterifying
residues
The saponification organic layer residue (30 mg) was treated
with triethylamine (three drops) and 4-bromo-phenacyl bromide
(20 mg) in dried acetone (5 mL) for 2 h at room temperature. The
reaction mixture was evaporated to dryness, resuspended in H2O
(10 mL) and extracted with Et2O (20 mL). The resulting organic
phase was concentrated and its residue was fractionated by normal
4.8.1. Purgic acid C (3)
White powder: mp 124–126 ꢂC; [a 589
]
ꢀ46.8, [a 578 ꢀ49.5,
]
[
a
]
ꢀ55.3, [
a
]
ꢀ88.9, [a 365
]
ꢀ134.7 (c 0.19, MeOH); For 1H
546
436
and 13C NMR spectroscopic data, see Tables 1 and 2; positive ESIMS
m/z 1337 [M + Na]+, 1191 [M + Na ꢀ 146]+, 1045 [1191 ꢀ146]+, 883
[1045 ꢀ162]+, 737 [883 ꢀ146]+, 591 [737 ꢀ146]+; HRESIMS m/z
1337.5834 [M + Na]+ (calcd for C56H98O34Na+ requires 1337.5832).
phase HPLC on an ISCO column (150 ꢁ19 mm,
mporasil, 10 mm),
using hexane-AcOEt (7:3; flow rate 2.0 mL/min) to afford (ꢀ)-4-
bromophenacyl (2R,3R)-3-hydroxy-2-methylbutyrate (tR 12.8 min)
and (+)- 4-bromophenacyl (2S)-2-methylbutate (tR 6.4 min). Also,
4-bromophenacylester derivatives of acetic and dodecanoic acids
were collected (tR 1.7 and 14.0 min, respectively). This procedure
has been used to confirmed the absolute configuration for these
chiral esterifying residues (Pereda-Miranda and Hernández-Carlos,
2002): 4-bromophenyacyl (2S)-2-methylbutyrate: mp 40–42 ꢂC;
4.8.2. Purgic acid D (4)
White powder: mp 158–160 ꢂC; [
a
]
ꢀ19.3, [
a
]
ꢀ20.7,
589
578
[
a
]
546 ꢀ22.9, [
a
]
436 ꢀ38.6, [a 365
]
ꢀ57.1 (c 0.14, MeOH); For 1H and
13C NMR spectroscopic data, see Tables 1 and 2; positive ESIMS m/z
1343 [M + H]+, 1197 [M ꢀ 146]+, 1051 [1197 ꢀ146]+, 889
[1051 ꢀ162]+, 743 [889 ꢀ146]+, 597 [743 ꢀ146]+, 435
[597 ꢀ162]+, 289 [435 ꢀ146]+; HRESIMS m/z 1343.6324 [M + H]+
(calcd for C58H102O34 + H+ requires 1343.6325).
[a]D +18 (c 1.0, MeOH); GC–MS m/z 272 (6.8), 270 (7.3), 254 (3.8),
252 (3.8), 186 (2.1), 172 (8.6), 171 (100), 70 (9.7), 169 (88.7), 90
(13.9), 89 (23.4), 85 (11.5), 63 (5.3) 57 (19), 51 (2.3), 50 (2.9), 41
(8.5), 39 (9.4). 4-bromophenacyl (2R,3R)-3-hydroxy-2-methylbu-
4.9. Sugar analysis and identification of aglycones
tyrate: mp 56ꢀ59 ꢂC; [
a
]
D ꢀ6.0 (c 1.0 CHCl3); GC–MS m/z 118 (2.0),
115 (10), 101 (20), 84 (12), 73 (70), 60 (100).
20 mg of purgic acids C (3) and D (4) in 10 mL HCl 4 N were
independently refluxed at 90 ꢂC for 1 h. Then, the reaction mixtures

92
E. Bautista et al. / Phytochemistry Letters 17 (2016) 85–93
were diluted with 5 mL H2O and extracted with ether (3 ꢁ10 mL).
The aqueous phases were neutralized with 1 N KOH and extracted
with n-BuOH (2 ꢁ 5 mL), washed with H2O (3 ꢁ 5 mL), and
concentrated to give a colorless solid. Thiazolidine derivatives
4.11. Cytotoxicity and modulation of multidrug-Resistance assays
Cytotoxicity and MDR reversal fold of compound 2 were
determined by using the SRB assay. The cells were harvested at log
phase of their growth cycle and were treated in triplicate with
for the sugar constituents (2 mg) were prepared by reaction with L-
cysteine (0.5 mg) in pyridine (0.1 mL) at 100 ꢂC according to
previously described procedures (Hara et al., 1987; Miyase et al.,
1995). These reaction mixtures were converted into volatile
derivatives by treatment with chlorotrimethylsilane, and analyzed
various concentrations of the test samples (0.2–25 mg/mL) and
incubated for 72 h at 37 ꢂC in a humidified atmosphere of 5% CO2.
The assay was carried out under static conditions and the results
are expressed as the concentration that inhibits 50% control
growth (IC50). The values were estimated from a semilog plot of the
by GC–MS: DB-5MS (10 m ꢁ 0.18 mm, film thickness 0.18
mm); He,
30 cm/s, 2 mL/min; 100 ꢂC isothermal for 3 min, linear gradient to
300 at 20 ꢂC/min. Retention times for TMS thiazolidine derivatives
drug concentration (mg/mL) against the percentage of growth
inhibition. Vinblastine was included as a positive control drug. The
reversal effects as modulators were further investigated with the
same method. Parental MCF-7 and MDR MCF-7/Vin cells were
seeded into 96-well plates and treated with various concentrations
of common sugars were used as standards for GC identification:
fucose, tR 4.53; -rhamnose, tR 4.58 min; min; -quinovose tR
4.64 min; and -glucose tR 6.53 min. The organic layers were
D-
L
D
D
evaporated to dryness, dissolved in CHCl3 (3 mL), and treated with
CH2N2. The derivatized fractions were individually submitted to
of vinblastine (0.00064–10
glycolipids (dissolved in H2O/DMSO, 9:1) at 25 and 5
72 h (Figueroa-González et al., 2012). Reserpine (5 m
used as a positive control drug. The reversal fold (RF) value, as a
parameter of potency, was calculated from dividing IC50 of
vinblastine alone by IC50 of vinblastine in the presence of test
compounds.
m
g/mL) in the presence or absence of
g/mL for
g/mL) was
m
normal-phase HPLC (ISCO, 21.2 ꢁ 250 mm, 10
m
m), using isocratic
elution [n-hexane-CHCl3-Me2CO (5:4:1)] and
a
flow rate of
5 mL/min to give 6 mg of methyl ipurolate from compound 3
and 5.8 mg of methyl ipolearate from 4.
4.9.1. Methyl ipurolate [methyl (3S,11S)-dihydroxytetradecanoate]
Colorless needles; mp 67–69 ꢂC, [
a
]
+12.9 (c 1.5, CHCl3);
D
positive ESIMS/MS m/z 275 [M + H]+, 257 [M + H – H2O]+, 231 [M –
CH3(CH2)2]+, 103 [CH(OH)CH2CO2CH3]+, 73 [CH3(CH2)2CHOH]+; 13
NMR (CDCl3, 100 MHz) : 14.1 (C-14), 18.9, 25.6, 25.7, 29.6, 29.56,
Acknowledgements
C
We acknowledge the financial support by Dirección General de
Asuntos del Personal Académico, UNAM (IN215016) and Consejo
Nacional de Ciencia y Tecnología (CB220535). E. B. is grateful to
DGAPA for a postdoctoral scholarship. Authors are deeply indebted
to Laboratorios Mixim, S.A. de C.V. for the generous donation of the
Mexican scammony resin. Thanks are due to G. Duarte (Facultad de
Química, UNAM) and C. Márquez (Instituto de Química, UNAM) for
the recording of mass spectra.
d
29.7, 36.7, 37.6, 39.8, 41.4, 51.8 (OCH3), 68.1 (C-3), 71.7 (C-11), 173.5
(C-1). This compound was identified by comparison of its physical
and spectroscopic constants with published values (Ono et al.,
2010).
4.9.2. Methyl ipolearate [methyl (3S,11S)-dihydroxyhexadecanoate]
Colorless needless 72–74 ꢂC, [a D +10.5ꢂ(c 1.5, CHCl3); positive
]
ESIMS/MS m/z 303 [M + H]+, 285 [M + H – H2O]+, 231 [M –
CH3(CH2)4]+, 103 [CH(OH)CH2CO2CH3]+, 101 [CH3(CH2)4CHOH]+;
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