Physakengoses K-Q, seven new sucrose esters from Physalis alkekengi var. franchetii

Article abstract of DOI:10.1016/j.carres.2017.07.010

Seven sucrose esters, physakengoses K-Q (1–7) were isolated from the aerial parts of Physalis alkekengi var. franchetii. Their structures were elucidated on the basis of extensive spectroscopic analyses and chemical methods. These new compounds were teste

Full text of DOI:10.1016/j.carres.2017.07.010

Carbohydrate Research 449 (2017) 120e124
Contents lists available at ScienceDirect
Carbohydrate Research
journal homepage: www.elsevier.com/locate/carres
Physakengoses K-Q, seven new sucrose esters from Physalis alkekengi
var. franchetii
Chuan-Yang Zhang, Jian-Guang Luo**, Rui-Huan Liu, Ru Lin, Ming-Hua Yang, Ling-Yi Kong*
State Key Laboratory of Natural Medicines, Department of Natural Medicinal Chemistry, China Pharmaceutical University, Nanjing, 210009, PR China
a r t i c l e i n f o
a b s t r a c t
Article history:
Seven sucrose esters, physakengoses K-Q (1e7) were isolated from the aerial parts of Physalis alkekengi
var. franchetii. Their structures were elucidated on the basis of extensive spectroscopic analyses and
chemical methods. These new compounds were tested for their antimicrobial abilities against Staphy-
lococcus aureus, Bacillus subtilis, Pseudomonas aeruginosa and Escherichia coli. Among the isolated sucrose
esters, compounds 1e5 showed potent antibacterial activity with MIC values ranging from 2.16 to
Received 28 March 2017
Received in revised form
12 June 2017
Accepted 25 July 2017
Available online 28 July 2017
12.76 mg/mL.
© 2017 Published by Elsevier Ltd.
Keywords:
Physalis alkekengi var. franchetii
Solanaceae
Sucrose ester
Antibacterial activity
1. Introduction
2. Results and discussion
Physalis alkekengi var. franchetii (Solanaceae) (Chinese name:
“Jindenglong”) [1], is widely distributed and cultivated in Europe
and Asia [2]. The calyxes of P. alkekengi var. franchetii have been
used as a traditional Chinese medicine for treatment of sore
throat, cough, eczema, hepatitis, urinary problems and tumors [3].
Sucrose esters, structurally featured in sucrose and long fatty acid
ester [4,5], have captured the attentions of many researchers due
to their potent antibacterial and anti-inflammatory activities in
recent years [6e8]. In continuing phytochemical studies of
P. alkekengi var. franchetii, we have previously reported the isola-
tion and structural determination of ten new sucrose esters
physakengoses A-J [9], and most of them displayed potent anti-
bacterial activities. This prompted us to further search for bioac-
tive sucrose esters. As a result, 7 new sucrose esters, named
physakengoses K-Q, were isolated from the aerial parts of
P. alkekengi var. franchetii (Fig. 1). In this paper, we report the
isolation, structure elucidation and antibacterial activity of the
isolated sucrose esters from the aerial parts of P. alkekengi var.
franchetii.
2.1. Structural elucidation
Physakengose K (1, C38H64O15) was obtained as an amorphous
solid. The NMR data of 1 (Table 1) revealed that it contained signals
for sucrose and long chain fatty acid ester moieties [10,11]. The
presence of a sucrose unit was deduced from the analysis of the NMR
spectra (Table 1), which showed the anomeric CH signals of the
glucopyranose (dH 5.56, d, J ¼ 3.5 Hz, H-1; dC 91.3, C-1) and that of the
anomeric carbon of the fructofuranose (dC 103.4, C-20). Alkaline hy-
drolysis also confirmed the existence of sucrose. Analysis of its NMR
spectra (1H, 13C, HSQC and HMBC) and the comparison of NMR data
between compound 1 and physakengose G [9] allowed the identi-
fication of the acyl groups as myristyl, tigloyl, 3-methylbutanoyl and
acetyl. The positions of these groups were established by the HMBC
correlations from H-30 (dH 5.31) to C-1 (dC 175.1) of myristyl group,
from H-2 (dH 4.86) to C-1 (dC 173.7) of 3-methylbutanoyl group, from
H-3 (dH 5.41) toC-1 (dC 168.6) of tigloyl groupand fromH2-10 (dH 4.01,
4.09) to acetoxy carbonyl (dC 172.0) (Fig. 2). Thus, the structure of
compound 1 was assigned as 10-O-acetyl-2-O-(3-methylbutanoyl)-
30-O-myristyl-3-O-tigloylsucrose.
The NMR data (Table 1) of physakengose L (2, C35H58O15) and
physakengose M (3, C35H58O15) also showed characteristic signals
for sucrose and fatty acid ester. A comparison of the spectroscopic
data of 2 with those of physakengose B [9] revealed an overall
similarity except for the presence of signals attributable to an acetyl
* Corresponding author.
** Corresponding author.
E-mail addresses: luojg@cpu.edu.cn (J.-G. Luo), cpu_lykong@126.com
(L.-Y. Kong).
http://dx.doi.org/10.1016/j.carres.2017.07.010
0008-6215/© 2017 Published by Elsevier Ltd.

C.-Y. Zhang et al. / Carbohydrate Research 449 (2017) 120e124
121
Fig. 1. Structures of compounds 1e7.
unit [dH 2.04 (3H, s); dC 171.8, 20.6], and the downfield shift of H2-10
dH 3.92, 4.04) relative to those in physakengose B (dH 3.32, 3.46).
positive and Gram-negative bacteria, respectively. As shown in
Table 3, compounds 1e5 had potent positive bacteriostatic effect
both against Gram-positive and Gram-positive bacteria with MIC
(
The location of the acetyl unit was determined by analysis of HMBC
spectrum. The 1H and 13C NMR data (Table 1) of compound 3 closely
resemble those of 2. The differences between them were deter-
mined by the HMBC spectrum; the correlations from H-2 (dH 4.84)
to the carbonyl carbon of isobutyryl unit (dC 177.7) and from H-3 (dH
5.42) to the carbonyl carbon of tigloyl unit (dC 168.7) suggested that
the isobutyryl and tigloyl units were attached to C-2 and C-3,
respectively. Accordingly, the structures of compounds 2 and 3
were elucidated as 10-O-acetyl-30-O-dodecanoyl-3-O-isobutyryl-2-
O-tigloylsucrose and 10-O-acetyl-30-O- dodecanoyl-2-O-isobutyryl-
3-O-tigloylsucrose, respectively.
Physakengose N (4, C35H58O14), isolated as an amorphous solid,
contained one more CH2 than physakengose F [9]. The 1H and 13C
NMR data (Table 1) of 4 were almost superimposable with those of
physakengose F. A comprehensive study on the 1D and 2D NMR
spectra of compound 4 indicated that it had one more methylene
group in its fatty acid chain. Thus, the structure of 4 was identified
as 30-O-tridecanoyl-2, 3-di-O-tigloylsucrose.
values ranging from 2.16 to 12.76 mg/mL but compounds 6 and 7
had no antibacterial activity. These results revealed that the long
fatty acid chain attached to C-2 or C-30 played an important role in
the antibacterial activity.
3. Conclusion
Sucrose esters, characterized by containing long chain fatty
acids attached to the disaccharide, are relatively rare compounds
which have been isolated from the Solanaceae, Asteraceae, Can-
naceae, and Polygalaceae families [11]. Regarding antibacterial ac-
tivity, compounds 1e5 showed strong activity, but 6 and 7 were
inactive. These results indicate that long chain fatty acid esters
attached to sucrose are essential for the inhibitor of the strains
tested.
4. Experimental
The 1D and 2D NMR spectroscopic data of physakengose O (5,
C
34H58O14) showed highly similarity to those of physakengose E [9],
4.1. General experimental procedures
except for the positions of dodecanoyl and 3-methylbutanoyl units.
The HMBC correlations from H-2 (dH 4.84) to the carbonyl carbon of
dodecanoyl (dC 174.4) and from H-30 (dH 5.42) to the carbonyl car-
bon of 3-methylbutanoyl (dC 174.4) allowed us to formulate 5 as 2-
O-dodecanoyl-30-O-(3-methylbutanoyl)-3-O-tigloylsucrose.
Physakengoses P (6, C22H34O13) and Q (7, C22H36O13) were ob-
tained as amorphous solids. Their 1H and 13C NMR spectra (Table 2)
were similar to those of physakengoses F and E, except for the
absence of signals for dodecanoyl unit attached to C-30, which were
further confirmed by their molecular formulas. The further analysis
of their 2D NMR spectra allowed us to formulate 6 as 2, 3-di-O-
tigloylsucrose and 7 as 2-O-(3-methylbutanoyl)-3-O-tigloylsucrose,
respectively.
The optical rotation values were recorded on a Jasco P-1020
polarimeter and IR data were detected on a Bruker Tensor 27
spectrometer. 1D and 2D NMR experiments were carried out in
methanol-d4 on a Bruker Avance III NMR instrument at 500 MHz
(1H) and 125 MHz (13C), and TMS was set as the internal standard.
Agilent UPLC-Q-TOF (6520B) was used to acquire HRESIMS data.
HPLC analysis was performed on an Agilent 1260 Series instrument
equipped with a DAD detector and a Shim-pack VP-ODS column
(4.6 ꢀ 250 mm, i.d.). Silica gel (200e300 and 100e200 mesh,
Qingdao Marine Chemical Co., Ltd.), MCI gel (75e150
m
m, Mitsu-
m,
bishi Chemical Corporation, Tokyo, Japan), and ODS (40e63
m
Fuji) were used for column chromatography (CC). All chemical re-
agents used were analytical grade (Jiangsu Hanbon Science and
Technology Co., Ltd., Nanjing, China).
2.2. Antibacterial activity
The antibacterial activity of compounds 1e7 against S. aureus, B.
subtilis, P. aeruginosa and E. coli was tested using disk diffusion assay
with penicillin and streptomycin as positive controls for Gram-
4.2. Plant material
The aerial parts of P. alkekengi var. franchetii were collected in

122
C.-Y. Zhang et al. / Carbohydrate Research 449 (2017) 120e124
Table 1
13C NMR (125 MHz) and 1H NMR data (500 MHz) of compounds 1e4 in CD3OD.
Position
1
2
3
4
dC
dH (J in Hz)
dC
dH (J in Hz)
dC
dH (J in Hz)
dC
dH (J in Hz)
1
2
3
4
91.3
71.9
73.7
69.3
74.6
61.9
5.56, d (3.5)
4.86, dd (10.4, 3.6)
5.41, t (9.9)
3.67, t (9.7)
3.92, m
3.84, dd (12.0, 1.8)
3.77, m
4.09, d (11.6)
4.01, d (11.6)
91.3
72.4
73.2
69.0
74.7
61.9
5.61, d (3.5)
4.79a
5.41, t (9.9)
3.68, t (9.7)
3.90, m
3.85, dd (11.8, 2.8)
3.78, m
4.04, d (11.6)
3.92, d (11.6)
91.4
72.0
73.8
69.2
74.7
61.9
5.59 d (3.5)
4.84, dd (10.4, 3.6)
5.42, t (9.9)
3.70, t (9.7)
3.93, m
3.83, dd (12.1, 2.0)
3.78, m
4.08, d (11.5)
4.03, d (11.5)
91.9
72.7
73.8
69.2
74.5
61.9
5.59, d (3.3)
4.79, dd (10.4, 3.5)
5.47, t (9.9)
3.72, t (9.7)
3.94, m
3.86, dd (12.1, 1.8)
3.78, m
3.47, d (11.7)
3.34, d (11.7)
5
6a
6b
1a0
1b0
20
65.6
65.9
65.7
64.1
103.4
79.0
73.2
84.3
63.0
103.3
79.3
73.2
84.2
63.0
103.3
79.1
73.1
84.2
63.0
105.1
78.6
73.5
84.1
63.1
30
5.31, d (8.2)
4.31, t (8.3)
3.88, m
3.77, m
3.77, m
5.26, d (8.3)
4.30, t (8.3)
3.86, m
3.78, m
3.78, m
5.31, d (8.3)
4.32, t (8.4)
3.87, m
3.78, m
3.78, m
5.40, d (8.4)
4.31, t (8.5)
3.88, m
3.78, m
3.78, m
40
50
6a0
6b0
30-O-
1
Myrisb
175.1
34.8
Dodecac
175.1
34.8
Dodecac
175.1
34.8
Tridecad
175.1
34.9
2a
2b
3
4e11
12
13
14
2-O-
1
2a
2b
3
4
5
2.57, m
2.46, m
1.69, m
1.30a
2.58, m
2.45, m
1.69, m
1.30a
2.54, m
2.45, m
1.69, m
1.30a
2.56, m
2.46, m
1.69, m
1.30a
26.1
26.0
23.7e33.1
14.4
26.0
23.7e33.1
14.4
26.1
23.7e33.0
23.7e33.0
23.7e33.0
14.4
23.7e33.1
23.7e33.1
14.4
1.30a
0.90, t (6.9)
0.90, t (6.9)
1.30a
1.30a
0.90, t (6.8)
0.90, t (6.9)
3-MeBue
173.7
Tigf
168.4
128.9
i-Bug
177.7
35.1
Tigf
168.6
129.1
44.3
2.17, d (6.9)
2.18, d (7.2)
1.96, m
0.87, d (6.6)
0.87, d (6.6)
2.51, m
26.6
22.6
22.7
Tigf
168.6
129.6
138.9
14.4
12.2
Ac
140.7
14.6
12.0
i-Bug
177.9
35.2
19.1
19.5
6.85, q (6.5)
1.80a
1.79, br s
19.5
18.8
1.04, d (7.1)
1.08, d (6.9)
140.2
14.3
6.81, m
1.78, d (7.2)
1.75, br s
12.0
3-O-
1
2
3
4
Tigf
Tigf
168.7
129.6
138.9
14.3
12.2
Ac
168.8
129.6
138.7
14.5
2.53, m
1.11, d (6.9)
1.06, d (7.0)
6.87, q (6.7)
1.79, d (7.1)
1.82, br s
6.85, dq like (1.3, 7.0)
1.79, d (7.1)
1.82, br s
6.81, m
1.78, d (7.2)
1.79, br s
5
12.2
10-O-
1
Ac
171.8
20.6
172.0
20.6
172.0
20.6
2
2.09, s
2.04, s
2.09, s
a
Overlapped signals.
Myris ¼ myristyl.
b
c
d
e
f
Dodeca ¼ dodecanoyl.
Trideca ¼ tridecanoyl.
3-MeBu ¼ 3-methylbutanoyl.
Tig ¼ tigloyl.
g
i-Bu ¼ isobutyryl.
4.3. Extraction and isolation
The plant materials (3.0 kg) were extracted with 95% EtOH
(3 ꢀ 10 L) under reflux. After removing the solvents under reduced
pressure, the viscous residue (240.0 g) was obtained. The applica-
tion of 1H NMR spectroscopy-guided isolation prompted us to
narrow the scope of targeted sucrose esters to the Fr. D of PE layer
as reported earlier [9]. Thus, Fr. D (25.0 g) was further separated by
an MCI gel column using MeOH-H2O (30:10e90:10, v/v) as eluent
to yield six major subfractions (Frs. D1-D6). Fr. D4 (8.0 g) was
applied to an ODS column eluted with solvent system of MeOH-
H2O (70:30e90:10, v/v) to afford Frs. D4a-D4e. Fr. D4b was purified
by preparative HPLC using MeOH-H2O (85:15, v/v) as the mobile
phase to give compound 1 (8.0 mg, tR ¼ 16.3 min). Compounds 2
(20.0 mg, tR ¼ 18.1 min) and 3 (15 mg, tR ¼ 17.3 min) were obtained
from Fr. D4c by recycling-preparative HPLC eluted with MeOH-H2O
(80:20, v/v). The Fr. D4d was subjected to recycling-preparative
Fig. 2. Selected HMBC correlations of compound 1.
October 2014 from Fuyang city, Anhui province, People's Republic
of China, and identified by Prof. Mian Zhang. A voucher specimen
(No.PAF-20150422) was deposited in the Department of Natural
Medicinal Chemistry, China Pharmaceutical University.
HPLC with MeOH-H2O (80:20, v/v) to furnish
4 (4.0 mg,

C.-Y. Zhang et al. / Carbohydrate Research 449 (2017) 120e124
123
Table 2
13C NMR (125 MHz) and 1H NMR data (500 MHz) of compounds 5e7 in CD3OD.
Position
5
Position
6
7
dC
dH (J in Hz)
dC
dH (J in Hz)
dC
dH (J in Hz)
1
2
3
4
91.1
72.0
73.9
69.4
74.4
61.9
5.57, d (3.6)
4.84a
5.40, t (9.8)
3.68, t (9.6)
3.93, m
3.85, dd (12.3, 1.6)
3.78, m
3.54, d (11.8)
3.43, d (11.8)
1
2
3
4
90.7
72.8
74.0
69.3
74.3
61.8
5.63, d (3.5)
4.80a
5.52, t (9.8)
3.70, t (9.6)
3.99, m
3.85, dd (11.9, 1.7)
3.78, m
3.47, d (11.9)
3.28, d (12.0)
90.9
72.1
74.0
69.5
74.1
61.8
5.59, d (3.6)
4.86a
5.46, t (9.8)
3.66, t (9.6)
3.98, m
3.84, dd (12.0, 2.1)
3.78, m
3.56, d (11.9)
3.41, d (11.9)
5
5
6a
6b
1a0
1b0
20
6a
6b
1a0
1b0
20
64.3
63.1
63.3
105.0
78.5
73.4
84.1
63.1
105.8
77.3
75.3
83.9
63.5
105.8
77.6
75.4
83.9
63.6
30
5.42, d (8.4)
4.31, t (8.5)
3.88, m
3.78, m
3.78, m
30
4.20, d (8.7)
4.02, t (8.5)
3.75, m
3.78, m
3.78, m
4.19, d (8.7)
4.03, t (8.5)
3.77, m
3.78, m
3.78, m
40
40
50
50
6a0
6b0
2-O-
1
6a0
6b0
2-O-
1
Dodecab
174.4
35.2
Tigc
169.2
129.5
3-MeBud
173.8
44.3
2a
2b
3
4e11
12
3-O-
1
2
3
4
5
30-O-
1
2a
2b
3
2.23, t (7.4)
2.23, t (7.4)
1.50, m
2a
2b
3
4
5
3-O-
1
2
3
4
2.16, d (7.3)
2.14, d (7.0)
1.98, m
0.88, d (6.7)
0.88, d (6.7)
25.9
140.2
14.5
6.84, dd (6.9, 1.1)
1.79, s
1.79, s
26.7
22.6
22.7
Tigc
169.0
129.5
139.2
14.4
12.1
23.7e33.0
14.4
1.30a
0.90, t (6.8)
12.1
Tigc
Tigc
168.7
129.6
138.8
14.4
168.7
129.1
139.0
14.4
6.86, dq (7.1, 1.1)
1.80, d (7.2)
1.82, br s
6.84, dd (6.9, 1.1)
1.79, s
1.79, s
6.88, m
1.79, d (7.1)
1.82, s
12.2
5
12.0
3-MeBud
174.4
44.0
2.45, dd (15.1, 6.9)
2.32, dd (15.1, 7.4)
2.18, m
1.04, d (6.9)
1.02, d (6.9)
26.9
22.9
22.7
4
5
a
Overlapped signals.
b
c
Dodeca ¼ Dodecanoyl.
Tig ¼ tigloyl.
d
3-MeBu ¼ 3-methylbutanoyl.
1384, 1262, 1167 cmꢁ1 1H NMR and 13C NMR data (see Table 1);
;
Table 3
Minimum inhibitory concentration (MIC) of compounds 1e7 (
HRESIMS m/z 783.4132 [MþNa]þ (calcd for C38H64NaO15, 783.4137).
m
g/mL).a
Compounds
S. aureus
B. subtilis
P. aeruginosa
E. coli
4.3.2. Physakengose L (2)
1
2
3
4
5
6
7.56 0.33
6.33 0.34
9.05 0.54
12.76 0.87
6.68 0.51
>50.00
4.25 0.28
8.58 0.56
4.11 0.44
6.14 0.54
6.29 0.62
>50.00
6.57 0.23
3.61 0.43
4.45 0.34
5.80 0.32
2.35 0.25
>50.00
5.63 0.53
2.16 0.30
10.42 0.57
4.02 0.45
2.91 0.32
>50.00
Amorphous solid; [
a
]25Dþ38.0 (c 0.1, MeOH); UV lmax (log ε)
217 (4.03) nm; IR (KBr) nmax 3509, 2926, 2854, 1749, 1650, 1466,
1385, 1262, 1164 cmꢁ1 1H NMR and 13C NMR data (see Table 1);
;
HRESIMS m/z 741.3666 [MþNa]þ (calcd for C35H58NaO15, 741.3668).
7
>50.00
0.06 0.03
>50.00
0.13 0.05
>50.00
>50.00
Penicillinb
Streptomycinb
4.3.3. Physakengose M (3)
0.41 0.15
0.45 0.15
Amorphous solid; [
a
]25Dþ40.0 (c 0.1, MeOH); UV lmax (log ε)
a
215 (4.04) nm; IR (KBr) nmax 3435, 2926, 2855, 17496, 1650, 1467,
Values are represented as the means
SD based on three independent
1385, 1265, 1161 cmꢁ1 1H NMR and 13C NMR data (see Table 1);
;
experiments.
b
HRESIMS m/z 741.3669 [MþNa]þ (calcd for C35H58NaO15, 741.3668).
Penicillin and Streptomycin were used as positive controls.
4.3.4. Physakengose N (4)
tR ¼ 18.4 min) and 5 (17.0 mg, tR ¼ 19.4 min). Fr D6 (2.0 g) was
chromatographed by an ODS column eluted with MeOH-H2O
(30:70e70:30, v/v) to get four major subfractions (Frs. D6a-D6d).
Amorphous solid; [
a
]25Dþ35.0 (c 0.1, MeOH); UV lmax (log ε)
217 (3.92) nm; IR (KBr) nmax 3415, 2924, 2852, 1718, 1646, 1465,
1384, 1270, 1154 cmꢁ1 1H NMR and 13C NMR data (see Table 1);
;
Compounds
6
(10.0 mg, tR
¼
11.7 min) and 7 (15.0 mg,
HRESIMS m/z 725.3716 [MþNa]þ (calcd for C35H58NaO14, 725.3719).
tR ¼ 12.9 min) were obtained from Fr. D6b and Fr. D6c by prepar-
ative HPLC with MeOH-H2O (45:55, v/v), respectively.
4.3.5. Physakengose O (5)
Amorphous solid; [
a
]25Dþ36.0 (c 0.1, MeOH); UV lmax (log ε)
4.3.1. Physakengose K (1)
215 (3.99) nm; IR (KBr) nmax 3421, 2926, 2855, 1724, 1651, 1465,
Amorphous solid; [
214 (3.82) nm; IR (KBr) nmax 3430, 2926, 2854, 1746, 1650, 1465,
a
]25Dþ30.0 (c 0.1, MeOH); UV lmax (log ε)
1383, 1265, 1153 cmꢁ1 1H NMR and 13C NMR data (see Table 2);
;
HRESIMS m/z 713.3716 [MþNa]þ (calcd for C34H58NaO14, 713.3719).

124
C.-Y. Zhang et al. / Carbohydrate Research 449 (2017) 120e124
4.3.6. Physakengose P (6)
Streptomycin and penicillin were used as positive controls for
Amorphous solid; [
a
]25Dþ74.0 (c 0.1, MeOH); UV lmax (log ε)
Gram-positive bacteria and Gram-negative bacteria, respectively.
All of the antimicrobial assays were performed in triplicate.
215 (3.93) nm; IR (KBr) nmax 3384, 2926, 2724, 1711, 1649, 1440
1385, 1273, 1138 cmꢁ1 1H NMR and 13C NMR data (see Table 2);
;
HRESIMS m/z 529.1887 [MþNa]þ (calcd for C22H34NaO13, 529.1892).
Acknowledgements
4.3.7. Physakengose Q (7)
This research work was supported by Huahai Graduate Inno-
vation Program, the Program for Changjiang Scholars, Innovative
Research Team in University (IRT_15R63), and the Project Funded
by the Priority Academic Program Development of Jiangsu Higher
Education Institutions (PAPD).
Amorphous solid; [
a]25Dþ65.0 (c 0.1, MeOH); UV lmax (log ε)
215 (3.97) nm; IR (KBr) nmax 3413, 2922, 2851, 1707, 1649, 1384,
1265,1052 cmꢁ1; 1H NMR and 13C NMR data (see Table 2); HRESIMS
m/z 531.2045 [MþNa]þ (calcd for C22H36NaO13, 531.2048).
4.4. Alkaline hydrolysis
Conflict of interest
Compounds 1e7 (2.0 mg each), dissolved in 2M aqueous NH4OH
(2 mL), were heated at 50 ꢂC for 4 h. The reaction mixtures were
neutralized with 2 M formic acid to pH 3 and extracted with EtOAc
(3 ꢀ 3 mL). Then, the aqueous phase was repeatedly dried with the
method reported in the literature [8]. Co-TLC analysis (CHCl3: HAc:
H2O ¼ 3: 3.5: 0.5, Rf ¼ 0.41) in comparison with authentic sucrose,
indicated the presence of sucrose.
The authors declare no competing financial interests.
Appendix A. Supplementary data
HRESIMS, 1H NMR, 13C NMR, HSQC, and HMBC spectra of 1e7 are
available in Supporting information.
Supplementary data related to this article can be found at http://
dx.doi.org/10.1016/j.carres.2017.07.010.
4.5. Antimicrobial assay
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