New solanocapsine-type tomato glycoside from ripe fruit of Solanum lycopersicum

Article abstract of DOI:10.1248/cpb.59.1403

A new solanocapsine-type tomato glycoside, a novel and interesting natural steroidal glycoside, was isolated from a mini tomato, Solanum lycopersicum L. The chemical structure of the new minor glycoside, esculeoside B-5 (3), was determined to be (5S,22R,23S,24R,25S)-22,26-epimino-16β,23-epoxy-3β, 23,24-trihydroxycholestane 3-O-β-lycotetraoside.

Full text of DOI:10.1248/cpb.59.1403

November 2011
Note
Chem. Pharm. Bull. 59(11) 1403—1405 (2011)
1403
New Solanocapsine-Type Tomato Glycoside from Ripe Fruit of
Solanum lycopersicum
a
b
,a
*
Mizuho OHNO, Masateru ONO, and Toshihiro NOHARA
a Faculty of Pharmaceutical Sciences, Sojo University; 4–22–1 Ikeda, Kumamoto 860–0082, Japan: and b School of
Agriculture, Tokai University; 5435 Aso, Kumamoto 869–1404, Japan.
Received May 26, 2011; accepted August 18, 2011; published online August 23, 2011
A new solanocapsine-type tomato glycoside, a novel and interesting natural steroidal glycoside, was isolated
from a mini tomato, Solanum lycopersicum L. The chemical structure of the new minor glycoside, esculeoside
B-5 (3), was determined to be (5S,22R,23S,24R,25S)-22,26-epimino-16b,23-epoxy-3b,23,24-trihydroxycholestane
3-O-b-lycotetraoside.
Key words tomato fruit; Solanum lycopersicum; solanocapsine-type glycoside; tomato glycoside
For metabolic analysis of steroidal glycosides,1) we se- local Italian tomatoes, processed tomato products, and im-
lected the tomato as part of our systematic investigation of ported canned tomatoes, tomato juice, and ketchup is cur-
the constituents of Solanum plants.2) We recognized that the rently in progress.
tomato would be appropriate because we were convinced that
Esculeoside B-1 (2) is the first example of a solanocap-
it had steroidal glycosides, as its aerial parts and immature sine-type steroidal alkaloid glycoside, the fundamental skele-
fruits are rich sources of tomatine. Hence, we isolated ton of which is very rare and interesting in terms of its chem-
steroidal glycosides from the ripe fruit. In Japanese tomatoes, ical structure and unknown pharmacological activity.
mini tomatoes, Momotaro tomatoes, and midi tomatoes, we
Here, we report one example of its rare solanocapsine-type
were the first to identify a steroidal saponin named esculeo- glycoside, esculeoside B-5 (3). A commercial mini tomato
side A (1) as a major tomato saponin in a yield of 0.0015— was blended briefly with water by a mixer and filtered with a
0.046%.3—5) From Italian tomatoes, we isolated esculeoside filter paper; the resulting filtrate was then passed through a
B-1 (2) in a yield of 0.019%.3,4)
highly porous polystyrene gel (Diaion HP-20) after elution
As other minor constituents of the ripe fruits of mini, midi, with water. The water eluate was discarded, and further elu-
and Momotaro tomatoes, we have isolated many steroidal tion with MeOH was performed to produce an eluate that
compounds so far by using various column chromatographies was evaporated to produce a residue. The MeOH eluate was
on Diaion HP-20, Chromatorex NH, and silica gel, as well as also subjected to reversed-phase silica gel column chro-
high-performance liquid chromatography on octadecylsilyl matography on ODS and elution with 60% MeOH, of which
(ODS) silica, as shown in Fig. 1.6—8)
the eluate was evaporated to give a residue. It consisted
Esculeoside B-1 (2) corresponds to an isomer of esculeo- almost entirely of esculeoside A; it was further chromato-
side A (1).9) Detailed investigation of the constituents of graphed on silica gel with CHCl3 : MeOH : H2Oꢀ7 : 3 : 0.5 to
Fig. 1. Steroidal Constituents in Ripe Fruits of Tomato Obtained in Our Group
© 2011 Pharmaceutical Society of Japan
∗ To whom correspondence should be addressed. e-mail: none@ph.sojo-u.ac.jp

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Vol. 59, No. 11
produce five fractions. Fraction 4 was was further rechro- 55.0, and 31.1; two quaternary carbons at d 37.0 and 44.1;
matographed on silica gel with CHCl3 : MeOH : H2Oꢀ6 : 4 : 1 four oxygen-bearing methine carbons at d 71.6, 78.9, 97.6,
to provide a steroidal glycoside, esculeoside B-5 (3).
and 88.0; one nitrogen-bearing methine carbon at d 59.7; one
Esculeoside B-5 (3) was obtained as an amorphous pow- acetal carbon at d 97.6; and one acetyl group at d 18.2 and
der having [a]D ꢁ52.5° (pyridine). Positive fast atom bom- 169.2. The heteronuclear multiple bond coherence (HMBC)
bardment mass spectroscopy (FAB-MS) revealed a quasimol- correlations around the steroidal D, E, and F rings are from
ecular ion peak at m/z 1130.5357 due to [C52H85NO24Na: H3-21 at d 1.58 to C-17 at d 59.7, C-20 at d 31.1, and C-22
1
1130.5359]ꢂ. The H-NMR (in pyridine-d5) spectrum of 3 at d 59.7; from H3-27 at d 1.16 to C-25 at d 36.2, C-26 at d
indicated two tertiary methyl groups at d 0.62 (3H, s) and 41.1, and C-24 at d 88.0; from H-24 at d 5.66 to C-23 at d
0.68 (3H, s) and two secondary methyl groups at d 1.16 (3H, 97.6; and from H-22 at d 3.57 (1H, d, Jꢀ7.8 Hz) to C-23 and
d, Jꢀ6.9 Hz) and 1.58 (3H, d, Jꢀ7.3 Hz), which are charac- C-26. These results revealed that esculeoside B-5 (3) has the
teristic of a typical steroidal sapogenol. We also observed fundamental skeleton of a solanocapsine-type glycoside, as
one acetyl signal at d 2.13 (3H, s); two nitrogen-bearing shown in Fig. 2. Moreover, nuclear Overhauser enhancement
methylene protons at d 2.98 (1H, dd, Jꢀ2.7, 10.4 Hz) and was observed between H-20 at d 3.60 (m) and H-22 at d
3.04 (1H, t-like, Jꢀ10.4 Hz); one acetoxyl-bearing methine 3.57, and between H3-27 at d 1.16 and OAc at d 2.13. Since
proton at d 5.66 (1H, d, Jꢀ7.8 Hz); and four anomeric proton the proton signal of H3-21 is shifted down slightly to d 1.58
signals at d 4.90 (1H, d, Jꢀ7.2 Hz), 5.20 (1H, d, Jꢀ7.9 Hz), because of the 23-OH group, they lie in a 1,3-diaxial ori-
5.25 (1H, d, Jꢀ8.0 Hz), and 5.49 (1H, d, Jꢀ7.3 Hz). The 13C- entation. Therefore, the structure of esculeoside B-5 (3) is
NMR (in pyridine-d5) spectrum showed signals due to a b-ly- represented as (5S,22R,23S,24R,25S)-22,26-epimino-16b,23-
cotetraosyl moiety at d 103.6 (gal C-1), 74.3 (gal C-2), 76.2 epoxy-3b,23,24-trihydroxycholestane 3-O-b-lycotetraoside,
(gal C-3), 82.5 (gal C-4), 77.6 (gal C-5), 61.8 (gal C-6), as shown in Fig. 3. This compound might be biosynthesized
106.3 (inner glc C-1), 81.0 (inner glc C-2), 88.6 (inner glc C- from lycoperoside G.9)
3), 76.9 (inner glc C-4), 79.8 (inner glc C-5), 63.7 (inner glc
Solanocapsine-type glycosides such as esculeoside B-5 (3)
C-6), 106.1 (term. glc C-1), 76.8 (term. glc C-2), 79.8 (term. are novel and interestingvery natural products.
glc C-3), 72.3 (term. glc C-4), 78.8 (term. glc C-5), 64.1
(term. glc C-6), 106.0 (xyl C-1), 76.5 (xyl C-2), 78.6 (xyl C-
Experimental
General Procedure Optical rotations were measured with a JASCO P-
3), 71.8 (xyl C-4), and 68.5 (xyl C-5). When these signals
were subtracted, 29 signals remained. They consisted of four
methyl carbons at d 13.4, 15.1, 18.8, and 24.9; nine methyl-
ene carbons at d 22.0, 30.1, 30.7, 33.4, 35.2, 35.8, 38.4, 39.2,
and 41.1; six methine carbons at d 36.2, 36.2, 46.0, 56.1,
1020 (lꢀ0.5) automatic digital polarimeter. FAB-MS were obtained with a
glycerol matrix in the positive ion mode using a JEOL JMS-DX300 and a
1
JMS-DX 303 HF spectrometer. The H- and 13C-NMR spectra were meas-
ured in pyridine-d5 with JEOL a-500 spectrometer, and chemical shifts are
given on a d (ppm) scale with tetramethylsilane (TMS) as the internal stan-
dard. Column chromatographies were carried out on a Diaion HP-20 (Mi-
tsubishi Chemical Ind., Japan), and silica gel 60 (230—400 mesh, Merck,
Germany). TLC was performed on silica gel plates (Kieselgel 60 F254
,
Merck) and RP C18 silica gel plates (Merck). The spots on TLC were visual-
ized by UV light (254/366 nm) and sprayed with 10% H2SO4, followed by
heating.
Extraction and Isolation of Compound 3 Commercial mini tomato
(783 g) was blended with water using a mixer for a short time (10—20 s) and
filtered using filter paper to obtain a filtrate. The filtrate was then passed
through a highly porous polystyrene gel (Diaion HP-20) and first eluted with
water. The water eluate was discarded, and elution was then carried out
using MeOH to obtain an eluate. This eluate was evaporated to obtain a
residue (23.4 g), which was subjected to reversed-phase silica gel column
chromatography, ODS, eluting with 60% MeOH, the eluate of which was
evaporated to obtain the residue (6.8 g). That residue was then chro-
matographed on silica gel with CHCl3 : MeOH : H2Oꢀ7 : 3 : 0.5 to obtain
five fractions. Fraction 2 was almost composed of esculeoside A (320 mg).
Furthermore, fraction 4 was rechromatographed on silica gel with CHCl3–
MeOH–H2Oꢀ6 : 4 : 1 to provide a steroidal glycoside, esculeoside B-5 (3,
12 mg).
Fig. 2. Key HMBC and NOESY around D, E, F-Rings
Esculeoside B-5 (3) An amorph. powder, [a]D ꢁ52.5° (cꢀ0.5, pyri-
dine).
Positive high resolution (HR)-FAB-MS (m/z): 1130.5357 (Calcd for
C52H85NO24Na: 1130.5359).
1H-NMR (pyridine-d5) d: 0.62 (3H, s, H3-19), 0.68 (3H, s, H3-18), 1.16
(3H, d, Jꢀ6.9 Hz, H3-27), 1.58 (1H, d, Jꢀ7.3 Hz, H3-21), 2.13 (3H, s, OAc),
2.98 (1H, dd, Jꢀ2.7, 10.4 Hz, Hb-26), 3.04 (1H, t-like, Jꢀ10.4 Hz, Ha-26),
3.57 (1H, d, Jꢀ7.8 Hz), 4.90 (1H, d, Jꢀ7.2 Hz, gal H-1), 5.20 (1H, d,
Jꢀ7.9 Hz, inner glc H-1), 5.25 (1H, d, Jꢀ8.0 Hz, xyl H-1), 5.49 (1H, d,
Jꢀ7.3 Hz, term. glc H-1), 5.66 (1H, d, Jꢀ7.8 Hz, H-24).
13C-NMR (pyridine-d5) d: 39.2 (C-1), 30.1 (C-2), 78.9 (C-3), 35.2 (C-4),
46.0 (C-5), 30.7 (C-6), 35.8 (C-7), 36.2 (C-8), 56.1 (C-9), 37.0 (C-10), 22.0
(C-11), 38.4 (C-12), 44.1 (C-13), 55.0 (C-14), 33.4 (C-15), 71.6 (C-16), 59.7
(C-17), 15.1 (C-18), 13.4 (C-19), 31.1 (C-20), 18.8 (C-21), 59.7 (C-22), 97.6
(C-23), 88.0 (C-24), 36.2 (C-25), 41.1 (C-26), 24.9 (C-27), 18.2, 169.2
(acetyl group), 103.6 (gal C-1), 74.3 (gal C-2), 76.2 (gal C-3), 82.5 (gal C-
4), 77.6 (gal C-5), 61.8 (gal C-6), 106.3 (inner glc C-1), 81.0 (inner glc C-2),
Fig. 3. Structure of Compound 3

November 2011
1405
88.6 (inner glc C-3), 76.9 (inner glc C-4), 79.8 (inner glc C-5), 63.7 (inner
glc C-6), 106.1 (term. glc C-1), 76.8 (term. glc C-2), 79.8 (term. glc C-3),
72.3 (term. glc C-4), 78.8 (term. glc C-5), 64.1 (term. glc C-6), 106.0 (xyl
C-1), 76.5 (xyl C-2), 78.6 (xyl C-3), 71.8 (xyl C-4), 68.5 (xyl C-5).
Sugar Analysis A solution of each compound (3) (3.0 mg) in 2 M
HCl : dioxane (1 : 1, 2 ml) was heated at 100 °C for 1 h. The reaction mixture
was diluted with H2O and evaporated to remove dioxane. The solution was
neutralized with Amberlite MB-3 and passed through a SEP-PAK C18 car-
tridge to give a sugar fraction. The sugar fraction was concentrated to dry-
ness in vacuo to give a residue, which was dissolved in CH3CN : H2O (3 : 1,
250 ml).The sugar fraction was analyzed by HPLC under the following con-
ditions: column, Shodex RS-Pac DC-613 (6.0 mm i.d.ꢃ150 mm, Showa-
Denko, Tokyo, Japan); solvent, CH3CN : H2O (3 : 1); flow rate; 1.0 ml/min;
column temperature, 70 °C; detection, refractive index (RI) and optical rota-
tion (OR). The tR (min) of sugars were as follow: D-xylose 4.2 (ꢂ), D-galac-
tose 7.0 (ꢂ), D-glucose 7.2 (ꢂ), [reference: D-xylose 4.2 (positive optical
rotation: ꢂ), D-galactose 7.0 (positive optical rotation: ꢂ), D-glucose 7.2
(positive optical rotation: ꢂ)].
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