Synthesis, biological activity of salidroside and its analogues

Article abstract of DOI:10.1248/cpb.58.1627

Salidroside is a phenylpropanoid glycoside isolated from Rhodiola rosea L., a traditional Chinese medicinal plant, and has displayed a broad spectrum of pharmacological properties. In this paper, about 18 novel salidroside analogues were prepared through Koenigs-Knorr method, the effects of these compounds over PC12 was assessed with the 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) method. The novel compounds differ in the substituents attached to the benzene ring or in the glycosyl donor. According to the data, compounds (3,5-dimethoxyphenyl)methyl β-D-glucopyranoside and (3,5-dimethoxyphenyl) methyl β-D-galactopyranoside with methoxy group at 3 and 5-positions of the benzene ring were the most viability at concentration of 300 μmol/l and 60 μmol/l, respectively.

Full text of DOI:10.1248/cpb.58.1627

December 2010
Note
Chem. Pharm. Bull. 58(12) 1627—1629 (2010)
1627
Synthesis, Biological Activity of Salidroside and Its Analogues
b
a
,a
Yibing GUO,a,c,# Yahong ZHAO,a,# Cheng ZHENG, Ying MENG, and Yumin YANG
*
a Jiangsu Key Laboratory of Neuroregeneration, Nantong University; b Institue of Nautical Medicine, Nantong University;
and c Medical School, Nantong University; No. 19, Qixiu Road, Nantong, Jiangsu 226001, P. R. China.
Received April 2, 2010; accepted September 15, 2010; published online September 30, 2010
Salidroside is a phenylpropanoid glycoside isolated from Rhodiola rosea L., a traditional Chinese medicinal
plant, and has displayed a broad spectrum of pharmacological properties. In this paper, about 18 novel salidro-
side analogues were prepared through Koenigs–Knorr method, the effects of these compounds over PC12 was as-
sessed with the 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) method. The novel com-
pounds differ in the substituents attached to the benzene ring or in the glycosyl donor. According to the data,
compounds (3,5-dimethoxyphenyl)methyl b-D-glucopyranoside and (3,5-dimethoxyphenyl)methyl b-D-galactopy-
ranoside with methoxy group at 3 and 5-positions of the benzene ring were the most viability at concentration of
300 mmol/l and 60 mmol/l, respectively.
Key words salidroside; analogue; 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide method; hypoglycemia and
serum limitation; PC12 cell
Salidroside, a traditional Chinese medicine, was known as to search for more activity compounds, 20 compounds (Fig.
the main bioactive component in the root of Rhodiola sacha- 1, 4a—d, 5e—f, 4g—t) were successfully produced by
linensis A. BOR., and was reported to have many pharmaco- Koenigs–Knorr method.
logical properties, such as resisting anoxia,1) anti-radiation
The synthesis of the compounds 3a—t was completed,
and antifatigue,2,3) improving oxygen lack and postponing which starting from the corresponding acetobromo-sugars
ageing.4) In recent years, salidroside has been used in such (D-glucose, D-galactose) with the suitable substituted aro-
special posts as diver, astronaut, pilot and mountaineer to en- matic alcohol. The reaction was conducted in dry ethyl ether
hance the ability for survival in adverse environment.5) Fur- and dichloromethane for 10 h under dark with the presence
thermore, many researches revealed that it has the activities of Ag2CO3. The process was optimized in the presence of
of preventing cardiovascular disease6) and anti-tumor.7) How- 4 Å MS. Powdered MS 4 Å was dried at 140 °C under re-
ever, the resource of wild R. sachalinensis A. BOR. was on duced pressure for 1 d before use. The designed target com-
the edge of exhaustion.
pounds 4a—4t were obtained from 3a—4t by direct deacetyl-
Salidroside is a 2-(4-hydroxyphenyl)ethyl b-D-glucopyra- ation with CH3ONa/CH3OH in good yields (Chart 1, over
noside (Fig. 1, 5e) which may be synthesized by glucosyla- 90% to almost in quantitative). The catalytic hydrogenation
tion of tyrosol.8,9) Considerable effort has been devoted to the of 4e and f to remove the protection of benzyl in the phenol
isolation and assess of pharmacological properties, synthesis hydroxy group is operated by refluxed with 5% Pd/C and
and structure modification of salidroside is very few. In order HCOONH4 in anhydrous methanol (Chart 1).
According to 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenylte-
trazolium bromide (MTT) assay, after the PC12 cells were
exposed to hypoglycemia and serum limitation for 24 h, it
was found that hypoglycemia and serum limitation induced
significant decreases in cell viability of cultured PC12 cells,
as compared to that of control group. Exposure to hypo-
glycemia and serum limitation for 24 h was used to induce
PC12 cell injury in all experiments unless otherwise stated.
The cell viability of PC12 for each compound provide a
quantitative comparison of salidroside and its analogues.
MTT assay confirmed that the exposure to hypoglycemia and
serum limitation caused the cell viability loss in cultured
PC12 cells, and further showed that pretreatment with
salidroside and its analogues at different concentrations (60,
300, 1000 mmol/l) significantly attenuated the cell viability
loss evoked by hypoglycemia and serum limitation except 4i
and 4j, with 60 mmol/l 4t and 300 mmol/l 4s yielding an at-
tenuating effect close to that of control group. Overall, the
data indicated that 4s and 4t are more active in the assay,
which provided some insights into the design of new salidro-
side analogue.
Experimental
General Commercial reagents were used without further purification
unless otherwise stated. All melting points are uncorrected. 1H-NMR spectra
Fig. 1. Structure of Salidroside and Its Analogues
∗ To whom correspondence should be addressed. e-mail: yangym@ntu.edu.cn
© 2010 Pharmaceutical Society of Japan
#
These authors contributed equally to this work.

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Vol. 58, No. 12
Reagents: a) P, Br2, Ac2O; b) Ag2CO3, CH2Cl2, Et2O, rt, 10 h; c) NaOMe, MeOH, rt, 3 h; d) HCOONH4, 5% Pd/C, CH3OH, reflux, 6 h.
Chart 1. Synthetic Route for Salidroside and Its Analogues
Table 1. Experiment Data of Compounds
Compound Yield Compound Yield
mp
(°C)
d
Compound Yield Compound Yield
mp
(°C)
d
No.
(%)
No.
(%)
(C1-H)
No.
(%)
No.
(%)
(C1-H)
3a
3b
3c
3d
3e
3f
3g
3h
3i
52
62
66
61
58
60
61
64
55
52
4a
4b
4c
4d
5e
5f
4g
4h
4i
100
96
92
94
91
100
100
100
96
120—121 4.18 (Jϭ7.8 Hz)
3k
3l
70
72
68
58
55
62
35
42
63
65
4k
4l
96
91
92
95
90
96
94
93
95
92
121—122 4.5 (Jϭ7.85 Hz)
142—143 4.46 (Jϭ7.9 Hz)
149—150 4.5 (Jϭ8.05 Hz)
130—131 4.45 (Jϭ7.85 Hz)
160—161 4.52 (Jϭ7.89 Hz)
80—82
96—97
97—98
4.18 (Jϭ7.7 Hz)
4.17 (Jϭ7.8 Hz)
4.13 (Jϭ7.2 Hz)
3m
3n
3o
3p
3q
3r
3s
4m
4n
4o
4p
4q
4r
4s
159—160 4.15 (Jϭ7.8 Hz)
55—57 4.10 (Jϭ7.25 Hz)
164—165 4.38 (Jϭ7.32 Hz)
137—139 4.43 (Jϭ7.56 Hz)
136—138 4.53 (Jϭ7.2 Hz)
138—140 4.45 (Jϭ6.85 Hz)
—
4.46 (Jϭ7.47 Hz)
117—118 4.51 (Jϭ8.0 Hz)
146—148 4.45 (Jϭ8.0 Hz)
146—148 4.51 (Jϭ8.0 Hz)
150—152 4.45 (Jϭ8.0 Hz)
3j
4j
92
3t
4t
were recorded on a Bruker AC 400 instrument at 500 MHz, and the follow-
ing abbreviations are used for the description of the patterns: sϭsinglet,
dϭdoublet, tϭtriplet, mϭmultiplet. The 1H-NMR spectra were recorded
with tetramethylsilane (TMS, d 0.00) as the internal standard and were run
in dimethyl sulfoxide (DMSO) or D2O, J values are expressed in Hz. Flash
chromatography was performed on silica gel (200—300 mesh) (Hai Yang
Chemical Factory, Qingdao, Shangdong, P. R. China). Compounds 2a and b
were prepared through literature.10)
General Procedure for Compounds 4a—t A mixture of 2a or 2b
(2.05 g, 5 mmol) and alcohol (4 mmol) was dissolved in dry dichloro-
methane–ether (2 : 1, 15 ml) and 2 g 4 Å MS was added, then stirred at room
temperature under N2 atmosphere for 20 min. After that Ag2CO3 (1.4 g,
5 mmol) was added rapidly to the mixture and stirring continued for 10 h
avoid light. The reaction mixture was filtered and evaporated under reduced
pressure. The crude product was purified by column chromatography using
1 : 3 or 1 : 2 EtOAc–petroleum ether to afford a colourless gummy mass
3a—t (yield shown in Table 1). To a solution of compounds 3a—t (2.5
mmol) in MeOH (10 ml) was added NaOMe (10 mg), and the reaction mix-
ture was stirred at room temperature for 2 h. After that diluted with MeOH
and acidified with Amberlite IRA-120 (Hϩ) resin to pHϭ7. The reaction
mixture was filtered and evaporated to dryness under reduced pressure
afford 4a—t as white solid11) (Table 1).
(DMSO) d: 9.12 (1H, s), 7.02 (2H, d, Jϭ8.35 Hz), 6.66 (2H, d, Jϭ6.55 Hz),
4.75 (1H, s), 4.62 (1H, s), 4.51 (1H, s), 4.28 (1H, s), 4.10 (1H, d,
Jϭ7.25 Hz), 3.82—3.87 (1H, m), 3.62 (1H, s), 3.45—3.58 (3H, m), 3.27—
3.32 (3H, m), 2.70—2.74 (2H, m). IR (KBr) cmϪ1: 3268, 1630, 1614, 1246,
1079, 1020. Anal. Calcd for C14H20O7: C, 55.99; H, 6.71. Found: C, 56.08;
H, 6.77.
Cell Culture Rat PC-12 cells, obtained from the American Type Cul-
ture Collection (Manassas, VA, U.S.A.), were plated and maintained in high-
glucose Dulbecco’s modified Eagle’s medium (DMEM) supplemented with
10% horse serum, 5% fetal bovine serum (FBS), 100 U/ml penicillin, and
100 U/ml streptomycin in 5% CO2/air at 37 °C. After being pretreated with
60, 300, or 1000 mmol/l compounds synthesized above for 24 h, the cells
were subjected to hypoglycemia and serum limitation by replacing the cul-
ture medium with the glucose-free DMEM supplement with 1% horse serum
and 1% FBS, 100 U/ml penicillin, and 100 U/ml streptomycin, and in the
presence of compounds at original concentrations for another 24 h incuba-
tion.14) At the end of incubation, the MTT solution was added and further in-
cubated at 37 °C for 4 h followed by the addition of DMSO to dissolve the
resulting formazan. The absorbance (optical density (OD)) values were
measured by spectrophotometry at 570 nm with an EIX-800 Microelisa
reader (Bio-Tek Inc., U.S.A.).
Procedure for Compounds 5e and f 2-(4-Hydroxyphenyl)ethyl b-D-
Glucopyranoside (5e): A mixture of 4e (180 mg, 460 mmol), 5% Pd/C
(208 mg) and ammonium formate (0.15 g, 2.3 mmol) in MeOH (6 ml) was
stirred at refluxing for 6 h. Then filtered, concentrated and purified by col-
umn chromatography using 8 : 1 CHCl3–MeOH to give 125 mg (91%) of 5e.
The physical constants were in agreement with the literature.13)
Acknowledgments The financial supports of Hi-Tech Research and De-
velopment Program of China (863 Program, Grant no.2006AA02A128), Na-
ture Science Foundation of China (Grant no. 30970713), Basic Research
Program of Jiangsu Province (Grant no. BK2009518) and Program for New
Century Excellent Talents in University are gratefully acknowledged.
2-(4-Hydroxyphenyl)ethyl b-D-Galactopyranoside (5f): 5f was prepared
References and Notes
1) Chen Y. M., Chen J., Mao G. M., Fu J. Y., Zhejiang Prev. Med., 19,
1
from 4f in the same manner just as described above, white solid: H-NMR

December 2010
92—93 (2007).
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1629
(2H, s), 4.75 (1H, d, Jϭ4.50 Hz), 4.61 (1H, d, Jϭ5.10 Hz), 4.50 (1H, t,
Jϭ5.30 Hz), 4.27 (1H, d, Jϭ4.65 Hz), 4.11 (1H, d, Jϭ7.25 Hz), 3.84—
3.89 (1H, m), 3.56—3.62 (2H, m), 3.46—3.53 (2H, m), 3.30—3.33
(1H, m), 3.25—3.28 (2H, m), 2.77—2.79 (2H, m). IR (KBr) cmϪ1
:
3429, 2934, 1614, 1514, 1453, 1252, 1145, 1058. Anal. Calcd for
C21H26O7: C, 64.6; H, 6.71. Found: C, 64.52; H, 6.80. 2-(4-Hydroxy-
phenyl)methyl b-D-galactopyranoside (4h): 1H-NMR (D2O) d: 7.35
(2H, d, Jϭ8.37 Hz), 6.91 (2H, d, Jϭ8.37 Hz), 4.85 (1H, d,
Jϭ11.28 Hz), 4.65 (1H, d, Jϭ11.28 Hz), 4.43 (1H, d, Jϭ7.56 Hz), 3.91
(1H, d, Jϭ3.03Hz), 3.73—3.85 (2H, m), 3.59—3.69 (2H, m), 3.49—
3.55 (1H, m). IR (KBr) cmϪ1: 3438, 1250, 1162, 1040. Anal. Calcd for
C13H18O7: C, 54.54; H, 6.34. Found: C, 54.62; H, 6.48. (4-
Chlorophenyl)methyl b-D-glucopyranoside (4i): 1H-NMR (D2O) d:
7.47 (4H, s), 4.93 (1H, d, Jϭ11.55 Hz), 4.53 (1H, d, Jϭ7.20 Hz), 3.93
(1H, d, Jϭ11.55 Hz), 3.76 (2H, s), 3.41—3.46 (4H, m). IR (KBr)
cmϪ1: 3355, 2930, 1599, 1492, 1466, 1208, 1078, 1042. Anal. Calcd
for C13H17ClO6: C, 51.24; H, 5.62. Found: C, 51.12; H, 5.68. (3,5-
Dimethoxyphenyl)methyl b-D-glucopyranoside (4s): 1H-NMR (D2O)
d: 6.73 (2H, s), 6.58 (1H, s), 4.89 (1H, d, Jϭ12 Hz), 4.74 (1H, d,
Jϭ12.5 Hz), 4.51 (1H, d, Jϭ8 Hz), 3.94 (1H, d, Jϭ12 Hz), 3.84 (6H,
s), 3.70—3.75 (1H, m), 3.38—3.49 (3H, m), 3.31 (1H, t, Jϭ8.5Hz). IR
(KBr) cmϪ1: 3377, 2938, 2836, 1596, 1472, 1210, 1160, 1038, 1012.
Anal. Calcd for C15H22O8: C, 54.54; H, 6.71. Found: C, 54.72; H, 6.80.
(3,5-Dimethoxyphenyl)methyl b-D-galactopyranoside (4t): 1H-NMR
(D2O) d: 6.74 (2H, s), 6.59 (1H, s), 4.90 (1H, d, Jϭ12 Hz), 4.75 (1H,
d, Jϭ12.5 Hz), 4.45 (1H, d, Jϭ8 Hz), 3.92 (1H, s), 3.85 (6H, s), 3.77—
3.81 (2H, m), 3.61—3.69 (2H, m), 3.59 (1H, t, Jϭ8 Hz). IR (KBr)
cmϪ1: 3384, 2937, 2878, 1601, 1473, 1208, 1157, 1048, 1017. Anal.
Calcd for C15H22O8: C, 54.54; H, 6.71. Found: C, 54.43; H, 6.58.
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1
11) Benzyl b-D-galactopyranoside (4b): H-NMR (DMSO) d: 7.38—7.40
(2H, d, Jϭ6.95 Hz), 7.30–7.35 (2H, m), 7.25–7.28 (1H, m), 4.89 (1H,
d, Jϭ4.85 Hz), 4.79 (1H, d, Jϭ12.30 Hz), 4.65 (1H, d, Jϭ5.45 Hz),
4.53–4.58 (2H, m), 4.33 (1H, d, Jϭ4.70 Hz), 4.18 (1H, d, Jϭ7.70 Hz),
3.64 (1H, t, Jϭ3.65 Hz), 3.49–3.57 (2H, m), 3.25–3.27 (1H, m). IR
(KBr) cmϪ1: 3412, 2943, 1650, 1454, 1418, 1211, 1141, 1077, 1040.
Anal. Calcd for C13H18O6: C, 57.77; H, 6.71. Found: C, 57.68; H, 6.80.
Phenethyl b-D-glucopyranoside (4c): 1H-NMR (DMSO) d: 7.25—7.29
(4H, m), 7.17—7.20 (1H, m), 3.91—3.96 (1H, m), 3.62—3.68 (2H,
m), 3.40—3.45 (1H, m), 4.91 (1H, d, Jϭ4.95 Hz), 4.86 (1H, d,
Jϭ4.86 Hz), 4.83 (1H, d, Jϭ5.10 Hz), 4.43 (1H, t, Jϭ6.0 Hz), 4.17
(1H, d, Jϭ7.80 Hz), 3.11—3.15 (1H, m), 3.07—3.10 (1H, m), 3.01—
3.05 (1H, m), 2.93—2.98 (1H, m), 2.83—2.87 (2H, m). IR (KBr)
cmϪ1: 3362, 1940, 1610, 1515, 1210, 1072, 1030. Anal. Calcd for
C14H20O6: C, 59.14; H, 7.09. Found: C, 58.98; H, 7.12. 2-(4-Benzyl-
oxyphenyl)ethyl b-D-glucopyranoside (4e): mp 96—98 °C. 1H-NMR
datum was in agreement with the literature.12) IR (KBr) cmϪ1: 3419,
2913, 2865, 1513, 1453, 1251, 1160, 1076, 1027. Anal. Calcd for
C21H26O7: C, 64.6; H, 6.71. Found: C, 64.72; H, 6.58. 2-(4-Benzyl-
oxyphenyl)ethyl b-D-galactopyranoside (4f): mp 127—128 °C. 1H-
NMR (DMSO) d: 7.43 (2H, d, Jϭ6.8 Hz), 7.36—7.39 (2H, m), 7.30—
7.33 (1H, m), 7.17 (2H, d, Jϭ8.7 Hz), 6.91 (2H, d, Jϭ8.7 Hz), 5.06
13) Deng M., Wu Z. G., Liu X. Y., Fourth Mil. Med. Univ., 28, 1501—
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