From the water-soluble extract of the leaves of Desmodium gangeticum, three phenolic glucosides were isolated. By means of spectroscopic methods they were identified as methyl salicylate β-D-glucopyranoside (1), leonuriside A (2) and syringaresinol-4'-O-β-D-glucopyranoside (3). These compounds were isolated for the first time from the genus Desmodium. Compound 1 significantly inhibited a-glucosidase in comparison with diabetic drug acarbose

Dang, Nguyen Hai

Dat, Nguyen Tien

Luyen, Nguyen Thi

English

Vietnam Academy of Science and Technology: Journals Online

 69 
VIETNAM JOURNAL OF CHEMISTRY         VOL. 53(2e) 69-72                                               APRIL 2015 
DOI: 10.15625/0866-7144.2015-2e-016 
  
 
 
PHENOLIC GLUCOSIDES FROM THE LEAVES OF  
DESMODIUM GANGETICUM (L.) DC 
Nguyen Tien Dat
*
, Nguyen Thi Luyen, Nguyen Hai Dang 
Institute of Marine Biochemistry, Vietnam Academy of Science and Technology  
Received 23 January 2015; Accepted for Publication 18 March 2015 
 
Abstract 
From the water-soluble extract of the leaves of Desmodium gangeticum, three phenolic glucosides were isolated. 
By means of spectroscopic methods they were identified as methyl salicylate β-D-glucopyranoside (1), leonuriside A 
(2) and syringaresinol-4'-O-β-D-glucopyranoside (3). These compounds were isolated for the first time from the genus 
Desmodium. Compound 1 significantly inhibited -glucosidase in comparison with diabetic drug acarbose. 
Keywords. Desmodium gangeticum, methyl salicylate β-D-glucopyranoside, leonuriside A, syringaresinol-4'-O-β-
D-glucopyranoside, -glucosidase 
 
 
1. INTRODUCTION 
 
Desmodium gangeticum (L.) DC. (Fabaceae) is 
a slightly woody perennial herb and widely 
distributed in South East Asia, India and Africa. In 
Vietnam, D. gangeticum has been used for various 
purposes such as hemostatic, antiseptic, urinary 
discharges, detoxication, anti-ophidic, anti-oedema 
[1]. In India, D. gangeticum has a considerable 
reputation as a bitter tonic, febrifuge, digestive, anti-
emetic, antipyretic and anticatarrhal, in 
inflammatory conditions of chest and in various 
other inflammatory conditions. It is also widely used 
in aryuveda for the treatment of neurological 
disorders. This plant is an accepted source of 
Shaliparni as per Ayurvedic Pharmacopoeia of India 
[2]. D. gangeticum is known to be rich in flavonoids, 
alkaloids, sterols and glycolipids with antioxidant, 
antibacterial, antidiabetic, antiulcer activities [2]. 
Most recently, Yadav et al. isolated a new aliphatic 
enone and a new bisindole alkaloid that inhibited 
TNF- and IL-6 in an LPS-stimulated macrophages 
model [3]. This might explain the anti-inflammatory 
activity of D. gangeticum in animal model [4]. In 
Vietnam, very few studies on the chemical 
constituents of D. gangeticum have been reported 
except for the qualitative identification of coumarin 
and flavonoid [5, 6]. In our continuing research on 
the chemical composition of D. gangeticum, we 
reported the presence of quercetin 3-O-β-D-
apiofuranosyl-(12)-[α-L-rhamnopyranosyl-
(16)]-β-D-galactopyranoside from leaves of this 
plant [7]. The present paper deals with the isolation 
and structural identification of methyl salicylate β-
D-glucopyranoside (1), leonuriside A (2) and 
syringaresinol-4'-O-β-D-glucopyranoside  (Fig. 1) 
from the water-soluble extract of the leaves of D. 
gangeticum. 
 
 
Fig. 1: Chemical structure of compounds 1-3 
isolated from the leaves of D. gangeticum 
 
2. EXPERIMENTAL 
 
2.1. General procedures 
 
Column chromatography was performed on 
silica gel 230-400 mesh (0.040-0.063 mm, Merck), 
YMC RP-18 (30-50 μm, Fujisilisa Chemical Ltd.), 
sephadex LH-20 and diaion HP-20 (Sigma-Aldrich). 
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VJC, Vol. 53(2e), 2015                                                                                                    Nguyen Tien Dat, et al. 
Thin layer chromatography was performed on DC-
Alufolien 60 F254 or RP18 F254 plates (Merck). 
Compound traces were visualized by UV light at 
254 and 366 nm, and by spraying with aqueous 10 % 
H2SO4 under heating for 5 minutes. Optical rotation 
was measured on a JASCO P-2000 polarimeter. 
NMR spectra were recorded on a Bruker AM500 
FT-NMR spectrometer using TMS as an internal 
standard. ESI-MS spectra were recorded on an 
Agilent 1260 series LC-MS single quadrupole.  
 
2.2. Plant materials 
 
The leaves of D. gangeticum were collected in 
Me Linh, Vinh Phuc province in April 2012, and 
identified by Prof. Tran Huy Thai, Institute of 
Ecology and Biological Resources (IEBR). Voucher 
specimens have been deposited at the herbarium of 
the IEBR. 
 
2.3. Extraction and isolation 
 
The air-dried and powdered leaves of D. 
gangeticum (5 kg) were extracted with MeOH at 
room temperature (15 L x 3 times). The methanol 
extract was evaporated to give a methanol residue 
(300 g) that was suspended in water and then 
partitioned successively with n-hexane and ethyl 
acetate to obtain n-hexane, ethyl acetate and water 
extracts, respectively. The water residue was passed 
through a diaion HP-20 column eluted by 0, 50 and 
100 % methanol in water. The 100 % methanol-
eluted fraction was chromatographed on a silica gel 
column using a gradient of 1-100 % methanol in 
chloroform to afford seven fractions B1B7. The 
B2 was fractionated on a sephadex LH-20 column to 
give two fractions B2.1 and B2.2. Fraction B2.1 was 
chromatographed on a silica gel column using 
chloroform-ethyl acetate-methanol (5:1:0.5 v/v) to 
obtain 3 (9 mg). Compound 1 (15 mg) was purified 
from B2.2 fraction by a silica gel column 
chromatography using mobile phase chloroform-
methanol-water (6:1:0.05 v/v). Fraction B3 was 
chromatographed on a YMC RP18 column eluted by 
methanol-water 1:1 to obtain 2 (12 mg).  
 
Methyl salicylate 2-O-β-D-glucopyranoside (1): 
white powder. 
1
H-NMR (500 MHz, DMSO-d6): H 
7.63 (1H, dd, J = 1.5, 8.0 Hz, H-3), 7.53 (1H, dd, J = 
1.5, 8.5, Hz, H-5), 7.25 (1H, d, J = 8.5 Hz, H-6), 
7.10 (1H, t, J = 8.0 Hz, H-4), 4.90 (1H, d, J = 7.5 
Hz, H-1'), 4.57 (1H, t, J = 5.5 Hz, H-5'), 4.10 (1H, 
dd, J = 5.5, 10.5 Hz, H-6'a), 3.79 (3H, br s, OMe), 
3.69 (1H, dd, J = 5.5, 10.5 Hz, H-6'b), 3.47 (1H, m, 
H-2'), 3.27 (2H, m, H-3',4'). 
13
C-NMR (125 MHz, 
DMSO-d6): C 156.1 (C-1), 121.2 (C-2), 130.2 (C-
3), 121.6 (C-4), 133.2 (C-5), 116.3 (C-6), 100.9 (C-
1'), 72.3 (C-2'), 76.4 (C-3'), 69.9 (C-4'), 77.1 (C-5'), 
60.9 (C-6'), 51.9 (OMe). ESI-MS (positive): m/z 315 
[M+H]
+
. 
 
Leonuriside A (2): white powder. 
1
H NMR (500 
MHz, DMSO-d6): δH 6.05 (2H, br s, H-3,5), 4.64 
(1H, d, J = 7.0 Hz, H-1'), 4.26 (1H, t, J = 5.5 Hz, H-
5'), 3.67 (6H, br s, OMe), 3.59 (1H, m, H-6'a), 3.41 
(1H, m, H-6'b), 2.99-3.16 (m, H-2', 3', 4'). 
13
C NMR 
(125 MHz, DMSO-d6): C 127.4 (C-1), 153.1 (C-2, 
C-6), 93.8 (C-3, C-5), 153.9 (C-4), 103.3 (C-1'), 
74.4 (C-2'), 76.4 (C-3'), 70.0 (C-4'), 77.0 (C-5'), 61.0 
(C-6'). ESI-MS (positive): m/z 333.2 [M+H]
+
. 
 
Syringaresinol-4'-O-β-D-glucopyranoside (3): 
colorless oil, []
25
D = –12,0 (c 0.01, MeOH); 
1
H-
NMR (500 MHz, CD3OD): δH 6.73 (2H, s, H-2', 6'), 
6.67 (2H, s, H-2, 6), 4.87 (1H, d, J = 7.5 Hz, H-1''), 
4.77 (1H, d, J = 4.0 Hz, H-7), 4.72 (1H, d, J = 4.5 
Hz, H-7'), 4.28 (2H, dd, J = 15.0, 9.0 Hz, H-9b, H-
9'b), 3.91 (2H, dd, J = 9.0, 3.0 Hz, H-9a, H-9'a), 3.86 
(6H, br s, 3',5'-OCH3), 3.85 (6H, br s, 3,5-OCH3), 
3.79 (1H, dd, J = 12.0, 2.5 Hz, H-6''a), 3.67 (1H, dd, 
J = 12.0, 5.5 Hz, H-6''b), 3.49 (1H, m, H-2''), 3.43 
(2H, m, H-3'', H-4''), 3.21 (1H, m, H-5''), 3.12 (2H, 
m, H-8, 8'). 
13
C-NMR (125 MHz, CD3OD): see 
Table 1. 
 
2.4. Assay for -glucosidase inhibition 
 
The -glucosidase (G0660-750UN, Sigma) 
enzyme inhibition assay was performed according to 
the previously described method [8]. Briefly, the 
sample solution (2 l dissolved in DMSO) and 0.5 
U/ml -glucosidase (40 l) were mixed in 120 l of 
0.1 M phosphate buffer (pH 7.0). After 5 min pre-
incubation, 5 mM p-nitrophenyl--D-
glucopyranoside solution (40 l) was added and the 
solution was incubated at 37 °C for 30 min. The 
absorbance of released 4-nitrophenol was measured 
at 405 nm by using a microplate reader (Molecular 
Devices, CA). Acarbose was used as positive 
control.
 
 
3. RESULTS AND DISCUSSION 
 
Compound 1 was isolated as an amorphous 
powder. The ESI-MS of 1 revealed the ion peak at 
m/z 315.5 [M+H]
+
. The 
1
H NMR showed four 
protons belonging to a 1,2-disubstituted benzene 
ring at δ 7.63 (1H, dd, J = 1.5, 8.5 Hz, H-3), 7.10 
(1H, t, J = 8.5 Hz, H-4), 7.53 (1H, dd, J = 1.5, 8.5 
 71 
VJC, Vol. 53(2e), 2015                                                                            Phenolic glucosides from the leaves… 
Hz, H-5) and 7.25 (1H, d, J = 8.5 Hz, H-6). A β-
linkage sugar moiety was also recognized based on 
the anomeric proton signal at δ 4.90 (1H, d, J = 7.5 
Hz, H-1'). The 
13
C-NMR and DEPT spectra of 1 
indicated the presence of 14 cacbon signals 
including a carboxylic at δ 166.4 (C-7), a methoxy at 
δ 51.9 (C-8), and six signals of  a glucose at δ  100.9 
(C-1′), 72,3 (2′), 76,4 (C-3′), 69,9 (C-4′), 77,1 (C-5′), 
60,9 (C-6′). By comparing these data with those 
reported, 1 was identified to be methyl salicylate β-
D-glucopyranoside [9]. 
Compound 2 was obtained as an amorphous 
powder and possesses molecular mass of 332 based 
on the ion peak at m/z 333.2 [M + H]
+
 in the ESI-MS 
spectrum. The 
1
H-NMR spectrum of 2 exhibited a 
two-proton singlet at δ 6.05 (2H, br s, H-3,5), which 
is characteristic of the symmetric tetra-substituted 
benzene ring. In addition, two methoxy groups at δH 
3.67 (6H, br s, OMe) and a β-glycosidic anomeric 
proton at δ 4.64 (1H, d, J = 7.0 Hz, H-1') were 
observed. The 
13
C-NMR and DEPT spectra of 2 
confirmed the presence of the symmetric tetra-
substituted benzene ring at  127.4 (C-1), 153.1 (C-
2, 6), 93.8 (C-3, 5), 153.9 (C-4) together with a β-D-
glucopyranoside moiety at  103.3 (C-1'), 74.4 (C-
2'), 76.4 (C-3'), 70.0 (C-4'), 77.0 (C-5'), 61.0 (C-6'). 
Thus 2 was determined as leonuriside A [10].  
 
Table 1: 
13
C-NMR data of compound 3 
Carbon 3
 Syringaresinol-4'-O-β-D-
glucopyranoside 
 
[11] 
1 139.7 139.5 
2, 6 105.0 104.8 
3, 5 154.6 154.4 
4 135.8 135.6 
7 87.8 87.1 
8 55.9 55.7 
9 73.1 72.8 
1' 133.2 133.0 
2', 6' 104.7 104.5 
3', 5' 149.5 149.3 
4' 136.3 136.2 
7' 87.3 87.5 
8' 55.9 55.4 
9' 73.1 72.9 
3, 5-OCH3 57.2 57.0 
3', 5'-OCH3 57.0 56.8 
1'' 105.5 105.3 
2'' 75.9 75.7 
3'' 78.0 77.8 
4'' 71.5 71.3 
5'' 78.5 78.3 
6'' 62.7 62.5 
Compound 3 was a colorless oil and its ESI-MS 
spectrum revealed the pick at m/z 581 [M+H]
+
. The 
1
H NMR spectrum of 3 showed signals 
representative for two aromatic symmetrical protons 
at δH 6.73 (2H, s, H-2', 6'), 6.67 (2H, s, H-2, 6), four 
methoxy groups at δH 3.86 (6H, br s, 3',5'-OCH3), 
3.85 (6H, br s, 3,5-OCH3) and a β-glycosidic 
anomeric proton at δH 4.87 (1H, d, J = 7.5 Hz, H-1''). 
The 
13
C-NMR and DEPT spectra of 3 revealed the 
presence of  a lignan with two assymetric aromatic 
rings together with two oxymethines (δC 87.5 and 
87.1), two oxymethylenes (δC 72.9 and 72.8), two 
methines (δC 55.7 and 55.9), and four methoxy 
groups. In addition, a glucose moiety was 
recognized at δC 105.5 (C-1''), 75.9 (C-2''), 78.0 (C-
3''), 71.5 (C-4''), 78.5 (C-5''), 62.7 (C-6''). From these 
data, compound 3 was identified as syringaresinol-
4'-O-β-D-glucopyranoside (tortoside A), a lignan 
widely found in plants [11].  
All the isolated compounds were tested for the 
-glucosidase inhibition. Compound 1 showed 
significant inhibitory effect (38 %) in comparison 
with antidiabetic agent acarbose (18 %) at the 
concentration 100 μg/ml. Compound 2 showed weak 
effect while 3 was inactive (Fig. 2). It is known that 
methyl salicylate β-D-glucopyranoside (1) is a 
storage form of a defense signal against pathogens, 
releasing free salicylic acid (SA) to meet the 
requirements in plants for their pathogenic resistance 
[12]. This compound also exhibited  a promising 
treatment option for prevention or treatment of 
diabetes by lowering glucose levels [13]. 
Consistently, our result showed that methyl 
salicylate β-D-glucopyranoside inhibited -
glucosidase, an enzyme involved in the 
hyperglycemia.  
 
 
 
Fig. 2: -glucosidase inhibitory effects of 
compounds 1 and 2 
 
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VJC, Vol. 53(2e), 2015                                                                                                    Nguyen Tien Dat, et al. 
4. CONCLUSION 
 
A phytochemical investigation of the water-
soluble extract of the leaves of Desmodium 
gangeticum led to the isolation of three phenolic 
glucosides methyl salicylate β-D-glucopyranoside 
(1), leonuriside A (2) and syringaresinol-4'-O-β-D-
glucopyranoside (3). These compounds were 
isolated for the first time from the genus 
Desmodium. Compound 1 showed inhibitory activity 
against -glucosidase. 
 
Acknowledgements. This work is supported by a 
grant from the Vietnam National Foundation for 
Science and Technology Development (NAFOSTED-
104.01-2011.54). We thank the Institute of 
Chemistry for the NMR measurements. 
 
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Corresponding author:  Nguyen Tien Dat 
Institute of Marine Biochemistry, Vietnam Academy of Science and Technology  
18, Hoang Quoc Viet, Cau Giay, Hanoi, Vietnam 
E-mail: ngtiend@imbc.vast.vn. 


Phenolic glucosides from the leaves of Desmodium gangeticum (L.) DC

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Phenolic glucosides from the leaves of Desmodium gangeticum (L.) DC

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