Original Papers 1737
+
1
13
"
Na] (calcd. for C23H29O12, 521.1629); H and C NMR, see l Ta-
ble 1 and 2.
where S, SB, C, and CB are the absorbencies of the sample, the
blank sample, the control, and the blank control, respectively
22].
[
Confirmation of glycosyl units
Compounds 1–4 (2.0 mg) were hydrolyzed with 2 M TFA (1.5 mL),
Inhibitory activity to tyrosinase
heated for 3 h at 110°C and extracted with CHCl (3 × 1.5 mL). The
This assay was performed according to the procedure of Dai et al.
[23] with slight modifications, using L-tyrosine as a substrate. Ar-
butin (purity > 98%; Sigma) was used as a positive control.
3
aqueous layer was concentrated to dryness under a stream of ni-
trogen. The aqueous residue was redissolved in anhydrous pyri-
dine (1.0 mL), and L-cysteine methyl ester hydrochloride (3.0 mg)
was added to the solution of pyridine. The mixture was heated at
Supporting information
60°C for 2 h, and 0.5 mL n-trimethylsilyimidazole (TMSI) was
Biological experimental details as well as 1H, 13C, DEPT, COSY,
HSQC, HMBC NMR, UV, IR, CD, and HRESIMS spectra of new com-
pounds (1–4) are available as Supporting Information.
added, followed by heating at 60°C for 1 h. The reaction product
was analyzed by GC under the following conditions: GC: Agilent
7
890 A equipped with an H2 FID and a HP-5 quartz capillary
column (30 m × 320 µm×0.25 µm); column temperature: 150–
50°C with the rate of 10°C/min; carrier gas: N (1 mL/min); split
2
Acknowledgements
2
ratio: 10:1; injection temperature: 280°C; detector tempera-
ture: 280°C; injection volume: 1.0 µL. The monosaccharides of
compounds 1–4 were confirmed by comparison of the retention
time of monosaccharides derivatives with those of standard sug-
ars (the standard sugars were subjected to the same reaction, D-
glucopyranose: 15.2 min; L-glucopyranose: 15.5 min).
!
Financial support by the Program for National Natural Science
Foundation of China (81302661), the Scientific Research Starting
Foundation (20121106) for Doctors of Liaoning province of P.R.
China, and the Foundation (L2012358) from the Project of Educa-
tion Department of Liaoning province of P.R. China is gratefully
acknowledged.
Enzymatic preparation of aglycones 1a and 2a
from 1 and 2
Compounds 1 and 2 (6.0 mg) were hydrolyzed with 20 mg of β-
glucosidase (E.C 3.2.1.21, Cat. No. G0395–5 KU, from almonds
Conflict of Interest
!
lyophilized powder, Sigma Inc.) in 1.5 mL of H O at 37°C for
The authors declare no conflict of interest.
2
10 h. The reaction mixture was extracted with n-BuOH. The n-
BuOH layer was evaporated in vacuo and subjected to semipre-
parative HPLC using 28% CH CN‑H O (4 mL/min) to give the agly-
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2
1
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3
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3
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8
•+
5
7
17 nm. ABTS radical cation (ABTS ) was produced by reacting
mM stock solution of ABTS with 2.45 mM potassium persulfate
47–654
(
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1
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•
+
dark at room temperature for 12–16 h before use. The ABTS so-
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7
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•+
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formula given below:
1
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•+
DPPH/ABTS scavenging activity (%) = [1 − (S−SB)/(C−CB)] × 100%
1
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