Batatins I and II, ester-type dimers of acylated pentasaccharides from the resin glycosides of sweet potato

Article abstract of DOI:10.1021/np070093z

Batatins I (1) and II (2), two ester-type dimers of acylated pentasaccharides, have been isolated by recycling HPLC from the hexane-soluble extract of sweet potato (Ipomoea batatas var. batatas). The structures were elucidated by a combination of high-resolution NMR spectroscopy and mass spectrometry. Complete analysis and unambiguous assignments of the ¹H and ¹³C NMR spectra of 1 and 2 were achieved by 2D shift correlation measurements. The glycosidic acid forming each branched pentasaccharide monomelic unit was confirmed as simonic acid B. Three different fatty acids esterify this core at the same positions in both batatins: C-2 on the second rhamnose unit and C-4 and C-2 (or C-3) on the third rhamnose moiety. The acylating residues were identified as (+)-(2S)-methylbutanoic, dodecanoic (lauric), and cinnamic acids. The site of lactonization by the aglycon in unit A was placed at C-3 of the second saccharide. The position for the ester linkage for monomelic unit B on the macrocylic unit A was identified as C-3 of the terminal rhamnose?. Through spectroscopic simulation of these complex oligosaccharides, the chemical shifts and coupling constants were deduced for the overlapped proton resonances with a non-first-order resolution. The experimental NMR spectroscopic values registered for batatinoside I (3), a new polyacylated macroyclic pentasaccharide also isolated from this plant, were used as the starting point for spectral simulation of 1 and 2. Both polymers 1 and 2 represent dimers of compound 3.

Full text of DOI:10.1021/np070093z

J. Nat. Prod. 2007, 70, 1029-1034
1029
Batatins I and II, Ester-Type Dimers of Acylated Pentasaccharides from the Resin Glycosides
of Sweet Potato†
Edgar Escalante-Sa´nchez and Rogelio Pereda-Miranda*
Facultad de Qu´ımica, UniVersidad Nacional Auto´noma de Me´xico, Ciudad UniVersitaria, Mexico City 04510 DF, Mexico
ReceiVed March 3, 2007
Batatins I (1) and II (2), two ester-type dimers of acylated pentasaccharides, have been isolated by recycling HPLC
from the hexane-soluble extract of sweet potato (Ipomoea batatas var. batatas). The structures were elucidated by a
combination of high-resolution NMR spectroscopy and mass spectrometry. Complete analysis and unambiguous
1
assignments of the H and 13C NMR spectra of 1 and 2 were achieved by 2D shift correlation measurements. The
glycosidic acid forming each branched pentasaccharide monomeric unit was confirmed as simonic acid B. Three different
fatty acids esterify this core at the same positions in both batatins: C-2 on the second rhamnose unit and C-4 and C-2
(or C-3) on the third rhamnose moiety. The acylating residues were identified as (+)-(2S)-methylbutanoic, dodecanoic
(lauric), and cinnamic acids. The site of lactonization by the aglycon in unit A was placed at C-3 of the second saccharide.
The position for the ester linkage for monomeric unit B on the macrocylic unit A was identified as C-3 of the terminal
rhamnose′′′. Through spectroscopic simulation of these complex oligosaccharides, the chemical shifts and coupling
constants were deduced for the overlapped proton resonances with a non-first-order resolution. The experimental NMR
spectroscopic values registered for batatinoside I (3), a new polyacylated macroyclic pentasaccharide also isolated from
this plant, were used as the starting point for spectral simulation of 1 and 2. Both polymers 1 and 2 represent dimers
of compound 3.
Native to tropical America, Ipomoea batatas (L.) Lam. var.
batatas (sweet potato, colloquially called “camote”1) is a perennial
morning-glory vine that has been cultivated for over 2000 years
for its edible tubers in Mexico, Central and lowland South
America, and the West Indies. It is thought that the cultivated
varieties originated in Mexico2 from a naturally occurring
hybridization event involving I. trifida (H.B.K.) G. Don and I.
tiliacea (Willd.) Choisy, which have similar lobed leaves and
growth habits but are not tuberous. Columbus introduced sweet
potatoes to Europe, and immediately after the 16th Century Spanish
Conquest, they were not just imported but cultivated in Spain and
Portugal, where they became staples long before the 18th century
popularization of the common potato (Solanum tuberosum L.) in
the rest of Europe.3 Outside of the Spanish Empire the sweet potato
was known only as a herbal remedy or as an exotic garden curiosity
during the 16th and 17th centuries, whereas today it is a popular
root vegetable that is grown in gardens and as a commercial
food crop throughout the world.4 The People’s Republic of
China, Indonesia, and Japan lead in the production of sweet
potatoes, and this tuber is now a common vegetable throughout
the Orient.5 In addition, some cultivars are propagated as ornamental
plants and some are used as ground cover in traditional agriculture
in Mexico.6
A decoction made from the leaves of this herbal drug is used in
folk remedies as gargles to treat mouth and throat tumors. Poultices
are prepared for inflammatory tumors.7 In Mexico, traditional
healers have long used leaf decoctions, considered to be of “cold-
nature”,8 to reduce excessive body heat,1 contemporarily defined
as such illnesses as fever, heart disease, dysentery, diarrhea, stomach
distress, gastrointestinal infection, and parasites. Previous to this
Results and Discussion
The present investigation describes the isolation of two ester-
type dimers, to which the names batatins I (1) and II (2) have been
given, and they were obtained from the hexane-soluble resin
glycosides of the high-starch content, white-fleshed, and white-
skinned staple-type cultivar “Picadito”. The new polyacylated
pentasaccharide batatinoside I (3), which was also isolated from
this mixture, forms the monomeric units described for both batatins.
A combination of high-resolution ESIMS, FABMS, and NMR
methods10 was used to elucidate the complex chemical nature of
these polymers. The registered values for compound 3 were used
investigation, the only known study of the resin glycosides of sweet
potato was conducted in Japan using the roots of a locally grown
Brazilian cultivar (cv. Simon), from which the structures of one
tetrasaccharide and four pentasaccharides (the simonin series)9 were
elucidated.
† This work was taken in part from the Ph.D. thesis of E. Escalante-
Sa´nchez.
* To whom correspondence should be addressed. Tel: +52-55-5622-
5288. Fax: +52-55-5622-5329. E-mail: pereda@servidor.unam.mx.
10.1021/np070093z CCC: $37.00
© 2007 American Chemical Society and American Society of Pharmacognosy
Published on Web 05/09/2007

1030 Journal of Natural Products, 2007, Vol. 70, No. 6
Escalante-Sa´nchez and Pereda-Miranda
Figure 1. Negative-ion MS/MS ESI-mass spectrum of batatin I (1). This technique provides an easily detectable [M - H]- peak (m/z
2761.61). All the characteristic ions resulting from glycosidic cleavage are clearly observed. The high-mass ion [M/2 - H]- (m/z 1379.79)
corresponds to the ester cleavage of the dimeric structure.
as the starting point to compare this macrocyclic pentasaccharide
with the two dimeric units of batatins I (1) and II (2), as well as
providing the chemical shifts and coupling constant values for the
1H NMR simulation work11 presented here.
elimination of the lipophilic esters14 and observed at m/z 1249 [M/2
- H - C9H6O] , m/z 1197 [M/2 - H - C12H22O] , and m/z 1067
-
-
[1249 - C12H22O]-. Each fragment represents the loss of cinnamoyl
(130 amu) and dodecanoyl (182 amu) residues, respectively. A
second major fragmentation for compounds 1 and 2 was produced
by glycosidic cleavage14,17 of the sugar moieties, yielding the shared
peaks at m/z 921 [1067 - C6H10O4 (methylpentose)]-, m/z 837
[921 - C5H8O (Mba) - C6H10O (methylpentose)]-, m/z 691 [837
- 146 (methylpentose)]-, m/z 545 [691 - 146 (methylpentose)]-,
and m/z 417 [545 - 128 (C6H8O3)]-.
1
A combination of H NMR spectra (Table 1) and 2D homo-
nuclear techniques (DQF-COSY and TOCSY)10 allowed all
C-bonded protons to be sequentially assigned within each ring
1
system (Table 1). The use of the H-detected {1H, 13C} one-bond
correlation experiment (HMQC)18 assigned all of the resonances
in the 13C NMR spectra (Table 2), where nine diagnostic signals
in the anomeric region (ca. 98 to 105 ppm) were registered. All
the signals assignable to the fatty acid groups, as well as those for
the fucose anomeric carbons of units A and B, plus those for the
2-methylbutanoate carbonyl carbons, were overlapped in both 1
and 2, giving, respectively, only one signal each in the 13C NMR
spectra. The diagnostic resonances observed in the downfield region
δ 4.80-6.40 (Table 1) were assigned to the anomeric protons
because their multiplicity for each signal is a doublet. A group of
paramagnetically shifted nonanomeric protons reflected the presence
of eight sites of esterification. The remaining region, where the
majority of the methine resonances for the oligosaccharide core
were found, was difficult to assign due to partial spectroscopic
overlap. However, expansion of the TOCSY spectrum for the region
δ 3.4-5.9 showed that at least one proton signal for each
monosaccharide unit was completely resolved. Therefore, edited
1H NMR subspectra10,15 for each individual monosaccharide moiety
were obtained and permitted the assignment of all resonances in
both monomeric units A and B. All NMR spectral data for
compound 3 were entirely superimposed with those registered for
compounds 1 and 2 except for those downfield shifted resonances
where there was a difference in the pattern of esterification in the
oligosaccharide cores.
Pure compounds 1-3 were submitted to saponification and
yielded a water-soluble glycosidic acid and an organic solvent-
soluble acidic fraction. The glycosidic acid was characterized as a
branched pentasaccharide and identified as simonic acid B: (11S)-
jalapinolic acid 11-O-R-L-rhamnopyranosyl-(1f3)-O-[R-L-rham-
nopyranosyl-(1f4)]-O-R-L-rhamnpyranosyl-(1f4)-O-R-L-rham-
nopyranosyl-(1f2)-â-D-fucopyranoside, which has been previously
identified in the resin glycosides of I. batatas,9 I. stolonifera,12 I.
murucoides,13 and I. pes-caprae.14 The liberated fatty acids were
identified as 2S-methylbutanoic, n-dodecanoic, and cinnamic acids.
In the negative ESIMS, batatins I (1) and II (2) showed the same
iodine adduct at m/z 2889.47 [M + I]-, which permitted the
calculation of the molecular formula C144H232O50, indicating that
these natural products represent a pair of diastereoisomers. A
quasimolecular ion was detected for both batatins at m/z 2761.61
[M - H]- and revealed that the molecular formula for these
compounds corresponds to two monomeric units of batatinoside I
(3, C72H117O25 [M + H]+, m/z 1381.78). To facilitate discussion,
each monomer was arbitrarily named unit A (macrocyclic moiety)
and unit B. Both compounds 1 and 2 shared the same peak at m/z
1379.79 [M/2 - H]- in their ESIMS (Figure 1), representing a
fragmentation pathway resulting from the cleavage of an ester-type
dimer linkage15 to form the high-mass fragment ion for the two
monomeric units.16 Other shared fragments were produced by the
The HMBC technique18 was used to locate the ester residues on
each monomeric unit, the position of lactonization on unit A, and
the position for the ester linkage forming the dimer-type structure.
The shielded carbonyl resonance at δ 174.7 was clearly assignable
to the lactone functionality because of its observed 2J-coupling with
the C-2 diastereotopic methylene protons of the aglycon unit A at
δH 2.25 and 2.84. The site of lactonization was corroborated at
3
C-3 of the second monosaccharide unit (Rha) by the observed J-
coupling between this lactone carbon and its geminal proton (δH

Acylated Pentasaccharides from Sweet Potato
Journal of Natural Products, 2007, Vol. 70, No. 6 1031
Table 1. 1H NMR Data of Compounds 1-3 (500 MHz)a
1
2
3
protonb
unit A
4.82 d (7.8)
4.52 dd (9.5, 7.8)
4.20*
unit B
4.81 d (7.9)
4.53 dd (9.6, 7.9)
4.20*
unit A
4.83 d (7.9)
4.54 dd (9.5, 7.9)
4.20*
unit B
Fuc-1
2
3
4.83 d (7.9)
4.54 dd (9.5, 7.9)
4.20*
4.82 d (7.8)
4.52 dd (9.5, 7.8)
4.19 dd (9.5, 3.4)
3.92 d (3.4)
3.82 q (6.3)
1.52 d (6.3)
4
5
6
3.92 d (2.5)
3.82 q (6.4)
1.52 d (6.4)
6.34 bs
3.92 d (2.0)
3.82 q (6.4)
1.52 d (6.4)
6.34 bs
3.92 d (2.5)
3.82 q (6.4)
1.52 d (6.4)
6.35 d (1.5)
5.32 bs
3.92 d (2.5)
3.82 q (6.5)
1.52 d (6.4)
6.35 d (1.5)
5.32 bs
Rha-1
2
6.33 d (1.3)
5.31 bs
5.31 bs
5.31 bs
3
4
5
6
5.63 dd (9.2, 1.6)
4.66 dd (9.2, 9.2)
5.02 dq (9.2, 6.3)
1.59 d (6.3)
4.42 dd (9.5, 3.1)
4.67 dd (9.5, 9.5)
5.02 dq (9.5, 6.3)
1.60 d (6.3)
5.64 dd (9.7, 2.4)
4.67 dd (9.7, 9.5)
5.04 dq (9.5, 6.3)
1.60 d (6.2)
5.63 bs
5.82 dd (3.0, 1.8)
4.63 dd (9.4, 3.0)
4.27 dd (9.6, 9.4)
4.40 dq (9.6, 5.9)
1.62 d (5.9)
5.94 d (1.5)
4.91*
5.85 dd (9.9, 3.0)
6.08 dd (9.9, 9.9)
4.48 dq (9.9, 6.3)
1.46 d (6.3)
5.66 d (1.1)
4.75 bs
4.43 dd (9.5, 3.1)
4.67 dd (9.5, 9.5)
5.04 dq (9.5, 6.2)
1.60 d (6.2)
5.65 d (1.8)
5.82 dd (3.0, 1.8)
4.63 dd (9.4, 3.0)
4.27 dd (9.6, 9.4)
4.40 dq (9.6, 6.0)
1.62 d (6.0)
5.94 d (1.5)
4.91*
5.84 dd (9.6, 3.2)
5.78 dd (9.6, 9.6)
4.44*
1.46 d (6.3)
5.63 bs
5.63 dd (9.9, 2.7)
4.66 dd (9.9, 9.9)
5.03 dq (9.9, 6.1)
1.59 d (6.1)
Rha′-1
2
3
4
5
6
Rha′′-1
2
3
4
5
6
Rha′′′-1
2
3
4
5
6
Jal-2
5.62 d (1.5)
5.64 d (1.8)
5.62 d (1.5)
5.81 dd (3.2, 1.5)
4.62 dd (9.5, 3.2)
4.27 dd (9.5, 9.5)
4.40 dq (9.5, 6.0)
1.61 d (6.0)
5.93 d (1.2)
4.91*
5.85 dd (9.9, 3.0)
6.08 dd (9.9, 9.9)
4.48 dq (9.9, 6.3)
1.46 d (6.3)
5.66 d (1.0)
4.92*
5.62 dd (7.6, 2.7)
4.23*
4.27 dq (9.5, 6.0)
1.72 d (6.0)
2.25 ddd (14.7, 7.1, 2.7)
2.84 ddd (14.7, 11.2, 2.4)
3.89 m
5.82 dd (3.0, 1.8)
4.59 dd (9.2, 3.0)
4.29 dd (9.2, 9.2)
4.36 dq (9.2, 6.0)
1.63 d (6.0)
5.81 dd (3.0, 1.5)
4.62 dd (9.3, 3.0)
4.27 dd (9.3, 9.3)
4.39 dq (9.3, 6.1)
1.61 d (6.1)
5.93 d (1.3)
4.91*
5.83 dd (9.9, 3.1)
6.07 dd (9.9, 9.9)
4.48 dq (9.9, 6.3)
1.46 d (6.3)
5.80*
5.99 dd (3.2, 2.2)
4.70 dd (9.3, 3.2)
5.77 dd (9.3, 9.3)
4.41*
1.53 d (6.9)
5.62 d (0.9)
4.77 bs
4.42 dd (9.2, 3.1)
4.20*
4.25 dq (9.2, 6.2)
1.72 d (6.2)
2.25 ddd (14.9, 6.6, 2.8)
2.86 ddd (14.9, 10.4, 1.7)
3.89 m
5.65 d (1.2)
4.75 bs
4.43 dd (9.3, 3.1)
4.20*
4.76 dd (3.3, 1.2)
4.42 dd (9.5, 3.3)
4.20 dd (9.5, 9.5)
4.25 dq (9.5, 5.9)
1.71 d (5.9)
2.26 ddd (15.1, 7.0, 3.7)
2.83 ddd (15.1, 10.9, 2.5)
3.89 m
5.62 dd (9.8, 2.4)
4.23*
4.27*
1.72 d (6.0)
2.33-2.43*
2.83 ddd (14.5, 11.0, 2.4)
3.89 m
4.25*
1.72 d (6.0)
2.33-2.48*
2.33-2.48*
3.89 m
11
16
1.00 t (6.9)
2.40 tq (7.0, 6.9)
1.15 d (7.0)
1.00 t (7.0)
2.42 tq (7.0, 6.8)
1.18 d (7.0)
1.00 t (6.9)
2.40 tq (7.1, 6.9)
1.15 d (7.1)
1.00 t (6.9)
2.40 tq (7.1, 6.9)
1.15 d (7.1)
0.90 t (7.4)
6.56 d (16.0)
7.85 d (16.0)
2.45 t (7.2)
0.88 t (7.0)
1.00 t (6.9)
2.40 tq (7.0, 6.7)
1.15 d (7.0)
0.90 t (7.4)
6.55 d (16.0)
7.84 d (16.0)
2.46 t (7.2)
0.88 t (7.3)
Mba-2
2 Me
3 Me
Cna-2
3
0.90 t (7.4)
0.92 t (7.4)
0.90 t (7.4)
6.55 d (16.0)
7.84 d (16.0)
2.46 t (7.3)
6.52 d (16.2)
7.75 d (16.2)
2.46 t (7.3)
6.56 d (16.0)
7.85 d (16.0)
2.45 t (7.2)
Dodeca-2
12
0.88 t (7.2)
0.87 t (7.1)
0.88 t (7.0)
a Data recorded in C5D5N. Chemical shifts (δ) are in ppm relative to TMS. The spin coupling (J) is given in parentheses (Hz). Chemical shifts
marked with an asterisk (*) indicate overlapped signals. Spin-coupled patterns are designated as follows: s ) singulet, d ) doublet, t ) triplet, m
1
b
) multiplet, q ) quartet, sept ) septet. All assignments are based on H-1H COSY and TOCSY experiments. Abbreviations: Fuc ) fucose;
Rha ) rhamnose; Jal ) 11-hydroxyhexadecanoyl; Mba ) 2-methylbutanoyl; Dodeca ) dodecanoyl; Cna ) trans-cinnamoyl.
5.63) in the pyranose ring.10 Esterification of macrocyclic unit A
by the acyclic unit B was identified by the observable 3J connectiv-
ity between the carbonyl group for the ester at δ 174.8 and the
proton at C-3 of the terminal rhamnose (Rha′′′, δH 5.62).
In batatin I (1), a nonanomeric proton signal (doublet of doublets,
Rha′′ H-2) paramagnetically shifted to δH 5.99 indicated the
presence of esterification at a different site than that observed in
compounds 2 and 3, as well as the 13C-1H long-range connectivity
(3JCH) between the carbonyl carbon (δC 166.8) of the trans-
cinnamoyl residue with this proton resonance in unit B. In batatin
II (2), 1H NMR signals of units A and B were almost superimpos-
able, indicating that the esterification sites in monomers A and B
are the same, so the conclusion was made that a trans-cinnamoyl
residue is located in the same Rha′′ position of both monomeric
units. Batatin II (2) represents a homodimer of the new batatino-
side I (3).
constants as possible were estimated from the 1H NMR spectrum.
In some cases, such as the triplet at ca. 6.08 ppm, the multiplicity
pattern was evident by visual inspection. In other cases, such as
the four-line pattern centered at ca. 5.81 ppm, an anomeric rhamnose
and two overlapping H-2 doublets of doublets for rhamnose signals
were uncovered by careful analysis. Where coupling constants could
not be estimated directly from the spectrum, rhamnose chemical
shifts and coupling constants from compound 3 were used as initial
estimates for the second-order analysis. The parameters were varied
until an optimal agreement between measured and calculated spectra
was achieved, as shown in Figure 2 for compound 1. This
methodology employed the MestRe-C program. A system of 24
nuclei was simulated for the proton signals located in the downfield
region between δ 4.75 to 6.40 for compound 1. NMR simulation
was applied where a visual NMR analysis was impossible, as in
the example of the multiple signal centered at δ 5.58-5.65. Here
the anomeric protons in both units A and B of Rha′ (blue) and
Rha′′′ (red) as well as the doublet of doublets for unit A proton
H-3 in Rha (purple) and Rha′′′ (red) moieties overlapped and
produced a non-first-order resolution. The superposition of the
simulated patterns for each monosaccharide unit duplicated this
complex signal in the measured 1H NMR spectrum (Figure 2). The
chemical shifts and coupling constants used to calculate the final
dimeric oligosaccharide spectra are summarized in Table 1.
Spectroscopic simulation was used to duplicate definitively the
1
registered H NMR (500 MHz) data and thus permit the correct
assignment for the chemical shifts and coupling constants of all
superimposed protons in 1 and 2. Chemical shifts were estimated
from TOCSY, COSY, and HMQC experiments. 1H NMR simula-
tion for each monosaccharide unit provided the correct chemical
shift and coupling constant values for the tightly coupled protons.10
In the case of the nonsuperimposed protons, as many of the coupling

1032 Journal of Natural Products, 2007, Vol. 70, No. 6
Escalante-Sa´nchez and Pereda-Miranda
Table 2. 13C NMR Data of Compounds 1-3 (125.7 MHz)a
resin glycosides has been identified in only two other morning-
glory species. The first of these yielded merremin, isolated from
the roots of Merremia hungaiensis,16 a Chinese medicinal plant.
The second yielded tricolorins H-J from the aerial parts of I.
tricolor, a species used as a cover crop in traditional agriculture in
the tropical zones of Mexico.15
It has been hypothesized that, in actuality, the resin glycosides
of Ipomoea species could form large, high molecular weight polar
polymers.16,19 Difficulties in their investigation have arisen from
their poor solubility in less polar organic solvents, which makes
isolation and purification problematic, except for more highly
acylated lipophilic resin glycosides such as the batatins. It is also
possible that these polymers aggregate in aqueous solutions and
form micelles, which could perturb cell membranes through an ion-
driven efflux provoking surface interactions with target cells. A
clue to this possibility is found in the example of the crystalline
state of tricolorin A.20
1
2
3
carbonb
unit A
101.6
unit B
101.6
unit A
101.6
unit B
101.6
Fuc-1
101.6
2
3
4
5
73.4
76.6
73.6
71.3
17.2
100.2
69.8
78.0
77.2
67.9
19.2
99.0
72.8
79.8
80.0
68.4
18.8
103.7
70.0
73.3
71.7
68.2
17.8
104.6
72.2
78.0
73.6
70.6
18.9
174.7
33.9
79.5
14.5
175.4
41.4
16.9
11.8
118.4
128.6
73.4
76.6
73.6
71.3
17.2
100.3
69.8
72.5
77.2
67.9
19.3
98.8
72.8
79.1
80.0
68.5
18.8
100.5
74.0
68.1
75.1
68.4
18.0
104.5
72.7
72.4
73.6
70.8
18.8
174.8
33.8
79.4
14.5
175.4
41.4
16.9
11.8
118.4
128.6
73.4
76.6
73.6
71.2
17.2
100.3
69.8
78.0
77.2
67.9
19.3
99.0
72.8
79.8
80.0
68.4
18.8
103.7
70.0
73.3
71.7
68.2
17.8
104.6
72.5
78.0
73.6
70.6
18.8
174.7
33.9
79.5
14.5
175.4
41.4
16.9
11.8
118.4
128.6
73.4
76.6
73.6
71.2
17.2
100.3
69.8
72.5
77.2
67.9
19.3
98.8
72.8
79.8
80.0
68.5
18.8
103.8
70.0
73.3
72.7
68.4
17.8
104.5
72.7
72.4
73.6
70.8
18.8
174.8
33.9
79.5
14.5
175.4
41.4
16.9
11.8
118.4
128.7
73.5
76.6
73.6
71.3
17.2
100.2
69.8
78.0
77.2
67.9
19.2
99.0
72.8
79.8
80.0
68.4
18.8
103.7
70.0
73.3
71.7
68.2
17.8
104.5
72.7
72.4
73.6
70.8
18.8
174.7
33.9
79.5
14.5
175.4
41.4
16.9
11.8
118.4
128.6
6
Rha-1
2
3
4
5
6
Rha′-1
2
3
4
5
6
Rha′′-1
2
3
4
5
6
Rha′′′-1
2
3
4
5
6
Jal-1
2
11
Experimental Section
General Experimental Procedures. All melting points were
determined on a Fisher-Johns apparatus and are uncorrected. Optical
rotations were measured with a Perkin-Elmer model 241 polarimeter.
1H (500 MHz) and 13C (125.7 MHz) NMR experiments were conducted
on a Bruker DMX-500 instrument. The NMR techniques were
performed according to previously described methodology.15 The
instrumentation used for HPLC analysis consisted of a Waters (Millipore
Corp., Waters Chromatography Division, Milford, MA) 600E multi-
solvent delivery system equipped with a photodiode UV detector
(Waters 996) at 254 nm. Positive-ion LRFABMS were recorded using
a matrix of triethanolamine on a JEOL SX102A spectrometer. Negative-
and positive-ion ESIMS experiments were performed on a VG Quattro
triple quadruple instrument (Micromass, Beverly, MA). Nitrogen was
used as both nebulizing and drying gas. Mass spectra were acquired
over a range of 100-3000 Da in 5 s/scan using electrospray ionization
with cone voltage set to 30 V. The sample was dissolved in 1:1 MeOH-
H2O with 0.1% formic acid and infused via syringe. High-resolution
FTMS data were acquired using a Bruker-Daltonics APEX II Fourier
transform mass spectrometer, equipped with a 9.4 T passively shielded
superconducting magnet and an external ESI ion source. GC-MS was
performed on a Hewlett-Packard 5890-II instrument coupled to a JEOL
SX-102A spectrometer. GC conditions: HP-5MS (5% phenyl)-
methylpolysiloxane column (30 m × 0.25 mm, film thickness 0.25 µm);
He, linear velocity, 30 cm/s; 50 °C isothermal for 3 min, linear gradient
to 300 °C at 20 °C/min; final temperature hold, 10 min. MS
conditions: ionization energy, 70 eV; ion source temperature, 280 °C;
interface temperature, 300 °C; scan speed, 2 scans s-1; mass range,
33-880 amu. NMR spectroscopic simulation was carried out with the
MestRe-C 4.0 program (Mestrelab Research, Santiago de Compostela,
Spain).
16
Mba-1
2
2-Me
3-Me
Cna-7
8
129.2 (× 2) 129.0 (× 2) 129.2 (× 2) 129.2 (× 2) 129.2 (× 2)
130.7 (× 2) 130.5 (× 2) 130.7 (× 2) 130.5 (× 2) 130.7 (× 2)
134.7
145.4
166.2
134.7
145.6
166.8
173.5
34.6
134.7
145.4
166.2
173.2
34.6
134.7
145.6
166.8
173.5
34.6
134.7
145.4
166.2
173.2
34.6
9
Dodeca-1 173.2
2
12
34.6
14.3
14.3
14.3
14.3
14.3
a Data recorded in C5D5N. Chemical shifts (δ) are in ppm relative
to TMS. All assignments are based on HMQC and HMBC experiments.
bAbbreviations: Fuc ) fucose; Rha ) rhamnose; Jal ) 11-hydroxy-
hexadecanoyl; Mba ) 2-methylbutanoyl; Dodeca ) dodecanoyl; Cna
) trans-cinnamoyl.
Plant Material. The roots of I. batatas var. batatas (cv. Picadito)
were collected in plantations in Salvatierra, Guanajuato, Mexico, in
1999. The plant material was identified by Dr. Robert Bye. A voucher
specimen (R. Bye FB 1314) was deposited in the Ethnobotanical
Collection of the National Herbarium (MEXU), Instituto de Biolog´ıa,
UNAM.
The glycolipid ester-type dimeric structure assigned for batatin
I (1) was (11S)-hydroxyhexadecanoic acid 11-O-R-L-[3-O-(11S-
hydroxyhexadecanoyl-11-O-R-L-rhamnopyranosyl-{2-O-(trans-
cinnamoyl)-4-O-(n-dodecanoyl)}-(1f4)-O-R-L-{2-O-(2-S-meth-
Extraction and Isolation. The powdered dry roots (2.6 kg) of I.
batatas var. batatas were extracted by maceration at room temperature
with hexane to give, after removal of the solvent, a dark orange syrup
(13.1 g). The crude extract prepared from the herbal drug was subjected
to column chromatography over silica gel (150 g) using gradients of
CH2Cl2 in hexane and Me2CO in CH2Cl2. A total of 185 fractions (200
mL each) were collected and combined to give several pools containing
mixtures of resin glycosides. The most lipophilic fractions (59-64),
eluted with CH2Cl2-Me2CO (7:3) and rich in resin glycosides, were
pooled and subjected to column chromatography over silica gel (30 g)
using a gradient of MeOH in CHCl3 to eliminate the pigmented residues.
The process was monitored by TLC, and a total of 20 fractions (20
mL each) were collected and combined, yielding from the fraction
eluted with CHCl3-MeOH (9:1) a mixture of lipophilic oligosaccha-
rides (945 mg).
ylbutanoyl)
(1f3)-O-R-L-rhamnopyranosyl}rhamnopyranosyl-
(1f4)-O-R-L-r-hamnopyranosyl-(1f2)-O-â-D-fucopyranoside]-
rhamnopyrano-syl-{3-O-(trans-cinnamoyl)-4-O-(n-dodecanoyl)}-
(1f4)-O-R-L-{2-O-(2S-methylbutanoyl)-(1f3)-O-R-L-
rhamnopyranosyl}rhamnopyranosyl-(1f4)-O-R-L-rhamnopyranosyl-
(1f2)-O-â-D-fucopyranoside-(1,3′′-lactone). The structure established
for its isomer batatin II (2) was (11S)-hydroxyhexadecanoic acid
11-O-R-L-[3-O-(11S-hydroxyhexadecanoyl-11-O-R-L-rhamnopyra-
nosyl-{3-O-(trans-cinnamoyl)-4-O-(n-dodecanoyl)}-(1f4)-O-R-L-
{2-O-(2-S-methylbutanoyl)(1f3)-O-R-L-rhamnopyranosyl}-
rhamnopyranosyl-(1f4)-O-R-L-rhamnopyranosyl-(1f2)-O-â-D-
fucopyranoside]rhamnopyranosyl-{3-O-(trans-cinnamoyl)-4-O-(n-
dodecanoyl)}-(1f4)-O-R-L-{2-O-(2S-methylbutanoyl)-(1f3)-O-R-
L-rhamnopyranosyl}rhamnopyranosyl-(1f4)-O-R-L-rhamnopyranosyl-
(1f2)-O-â-D-fucopyranoside-(1,3′′-lactone). This type of dimeric
Recycling HPLC Separation. The analytical HPLC separations
were done on a Symmetry C18 column (Waters; 5 mm, 4.6 × 250 mm)

Acylated Pentasaccharides from Sweet Potato
Journal of Natural Products, 2007, Vol. 70, No. 6 1033
Figure 2. Simulation of the anomeric region of the 1H NMR spectrum of batatin I (1). The top trace is the measured 500 MHz spectrum,
resolution enhanced. Peaks are color coded for each rhamnose and fucose monomers of units A and B. Actual chemical shifts are depicted
along the bottom of the top plots. Below are the simulated spectra for each of the units. The Hn descriptors denote a specific position for
each sugar unit.
with an isocratic elution of CH3CN-MeOH (9:1), a flow rate of 0.7
mL/min, and a sample injection of 20 mL (3 mg/mL). The crude fraction
was subjected to preparative HPLC on a reversed-phase C18 column
(7 mm, 19 × 300 mm). The elution was isocratic with CH3CN-MeOH
(9:1) using a flow rate of 9 mL/min. Eluates across the peaks with tR
of 20.2 min (peak I), 21.6 min (peak II), and 22.9 min (peak III) were
collected by the technique of heart cutting and independently reinjected
in the apparatus operated in the recycle mode21 to achieve total
homogeneity after 10-20 consecutive cycles employing the same
isocratic elution. These techniques afforded pure compounds 1 (17.3
mg) from peak II; 2 (14.6 mg) from peak I, and 3 (6.7 mg) from
peak III.
16.5 min), m/z [M]+ 148 (100), 147 (96), 131 (25), 103 (40), 102 (20),
77 (25), 74 (8), 51 (20), 50 (8), 39 (5), 38 (4); and n-dodecanoic acid
(tR 17.8 min), m/z [M]+ 200 (15), 183 (2), 171 (18), 157 (40), 143
(10), 129 (48), 115 (20), 101 (15), 85 (33), 73 (100), 60 (80), 57 (30),
55 (47), 43 (30). The preparation and identification of 4-bromophen-
yacyl (2S)-2-methylbutyrate21 from compounds 1-3 were performed
according to previously reported22 procedures: mp 40-42 °C; [R]D
+18 (c 1.0, MeOH); GC-MS (tR 4.75 min) m/z [M + 2]+ 272 (6.8),
[M]+ 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). The aqueous phase from each
reaction was extracted with n-BuOH (5 mL) and concentrated to give
a colorless solid. The residue was methylated with CH2N2 to yield
simonic acid B methyl ester. The physical and spectroscopic constants
(1H and 13C NMR) registered for this derivative9 were identical in all
aspects to those previously reported: white powder; mp 113-115 °C;
[R]D -82.5 (c 1.0, MeOH); HRFABMS m/z 1015.5322 [M - H]-
(calcd for C47H83O23 requires 1015.5325).
Batatin I (1): white powder; mp 117-120 °C; [R]D -38 (c 1.0,
1
MeOH); H and 13C NMR, see Tables 1 and 2; negative HRESIMS
m/z 2760.5654 [M - H]- (calcd for C144H231O50 +4.40 ppm).
Batatin II (2): white powder; mp 124-130 °C; [R]D -33 (c 0.1,
1
MeOH); H and 13C NMR, see Tables 1 and 2; negative HRESIMS
m/z 2760.5602 [M - H]- (calcd for C144H231O50 +2.50 ppm).
Batatinoside I (3): white powder; mp 126-130 °C; [R]D -24 (c
1.0, MeOH); 1H and 13C NMR, see Tables 1 and 2; negative FABMS
m/z 1379 [M - H]-, 1249 [M - H - C9H6O]-, 921, 837, 545, 417;
positive HRESIMS m/z 1381.7878 [M + H]+ (calcd for C72H117O25
+1.72 ppm).
Acknowledgment. This research was partially supported by Consejo
Nacional de Ciencia y Tecnolog´ıa (CONACyT: 45861-Q). E.E.-S. is
grateful to CONACyT for a graduate student scholarship. Thanks are
due to T. Gibson (University of Reading, UK), G. Duarte, and M.
Guzma´n (“Unidad de Servicios de Apoyo a la Investigacio´n”, Facultad
de Qu´ımica, UNAM) for the recording of mass spectra. We are grateful
to Dr. C. M. Cerda-Garc´ıa-Rojas (CINVESTAV, Instituto Polite´cnico
Nacional) for his advice during the NMR simulation studies. We also
wish to thank Dr. M. Fragoso-Serrano (Facultad de Qu´ımica, UNAM)
for technical assistance.
Alkaline Hydrolysis of Compounds 1-3. Individual solutions of
compounds 1-3 (10 mg) in 5% KOH-H2O (3 mL) were refluxed at
95 °C for 2 h. The reaction mixtures were acidified to pH 4.0 and
extracted with CHCl3 (10 mL). The organic layers were washed with
H2O, dried over anhydrous Na2SO4, and evaporated under reduced
pressure. Each residue was directly analyzed by GC-MS, and three
peaks were detected: 2-methylbutanoic acid (tR 7.2 min), m/z [M]+
102 (3), 87 (33), 74 (100), 57 (50), 41 (28), 39 (8); cinnamic acid (tR

1034 Journal of Natural Products, 2007, Vol. 70, No. 6
Escalante-Sa´nchez and Pereda-Miranda
feed for farm animals. The yellow and orange pigments in the pulp
of the tuber are carotenoids and therefore a rich source of vitamin
A. Over one-fourth is carbohydrates, mostly starch, but the sweet
taste indicates that sucrose is also present, especially in the watery
yams (3-6% w/w).
References and Notes
(1) The sweet potato is called “camote” in Mexico, the word deriving
from the Nahuatl “camohtli” and refering to an edible root or potato
of the family Convolvulaceae. In the Aztec treasury of herbal
remedies “De la Cruz-Badianus Manuscript” (1552) or “Little Book
of Indian Medicinal Herbs” (Libellus de Medicinalibus Indorum
Herbis) seven species of morning-glories were included with their
therapeutic descriptions in Latin. One of these illustrates (Folio 28
verso) a bindweed called “Tlacacamohtli” (Nahuatl, noble edible root,
“tlaca”, “tlacatl” ) noble) prescribed to cure heat in the heart (contra
cordis calorem) and also to reduce excessive heat of the body. The
illustration represents a tuberous rooted red-flowered Ipomoea species,
the sweet potato, as its indigenous name indicates. See: Emmart, E.
W. The Badianus Manuscript (Codex Barberini, Latin 241). An Aztec
Herbal of 1552; The Johns Hopkins Press: Baltimore, 1940; pp 252-
253.
(2) Dr. Francisco Herna´ndez (1515-1587), King Phillip II’s chief
medical officer in the Spanish colonies in the New World (1570-
1577), was the first trained scientist to gather ethnobotanical
information directly from Aztec healers and to assess the medicinal
usefulness of the natural resources found in the central area of
Mexico. He described the nutritious properties and the manner of
cultivation of “cacamotli” and mentioned four varieties named long
ago on the basis of their skin and flesh colors: “The root is sometimes
red on the outside and white inside, and is called “acamotli”. If the
outer skin is purple and the inner part white, it is called “ihaicamotli”.
If the outside is white and the inside yellow with a reddish tinge, it
is called “xochicamotli”. There are times when both the inside and
the outside are red or completely white, and then it is called
“camocpalcamotli” or “poxcauhcamotli”: names bestowed many
centuries ago according to the variety of the colors.” In contemporary
Mexico and Brazil, there are four cultivated varieties recognized by
their different skin colors: white, yellow, red, and purple. See:
Herna´ndez, F. The Mexican Treasury: The Writings of Dr. Francisco
Herna´ndez; Varey, S., Ed.; Stanford University Press: Stanford, 2000;
p 184.
(3) The awareness of the role played by the sweet potato in Europe was
not properly appreciated until recently due partially to a linguistic
confusion perpetuated by herbals. Whereas the native word “batata”
and “patata” were used in Spanish to indicate the sweet potato and
the common one, respectively, in English they were joined together
under the word “potato”, which was used to indicate both species.
Perhaps, the best known reference reinforcing this confusion comes
from John Gerard’s General History of Plants (1597), where he
asserted an Andean origin to the sweet potato (Sisarum peruVianum)
while claiming that the ordinary potato originated in the English
colony of Virginia (Battata Virginiana). The potato that William
Shakespeare mentions in the Merry WiVes of Windsor is the sweet
potato. See: Gerard, J. The Herbal or General History of Plants;
Dover: New York, 1975; pp 925-928.
(4) In the United States, two varieties are common: the dry, mealy,
“yellow sweet potato”, and the watery, orange “yam”, which in reality
is not a true yam (Dioscorea spp.). This root crop is generally eaten
boiled, baked, fried, or dried, and ground into syrup or flour to make
biscuits, bread, pastries, and candy. Tubers are also dehydrated into
“chips”, cooked, frozen, creamed, and used as pie fillings in the same
manner as pumpkins. The foliage and the tuber are also valued as
(5) Sweet potatoes are currently believed to have been brought to
Polynesia by sea from South America around 1000 B.C. Historical
records indicate that sweet potatoes were introduced into India,
Malaysia, Indonesia, and the Philippines in the 16th century, reaching
Fujian, mainland China in 1584. They first reached Japan at
Miyakojima Island, in 1597. Asia accounts for 90% of the world
production of 130 million tons, with China alone producing
86%.
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the Ancient Nahuas; University of Utah Press: Salt Lake City, 1988;
pp 270-282. (b) Ortiz de Montellano, B. R. Aztec Medicine, Health,
and Nutrition; Rutgers University Press: New Brunswick, NJ, 1990;
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