Flavonol glycosides from convolvulus supinus and their antioxidant activity

Full text of DOI:10.1007/s10600-013-0785-8

Chemistry of Natural Compounds, Vol. 49, No. 5, November, 2013 [Russian original No. 5, September–October, 2013]
FLAVONOL GLYCOSIDES FROM Convolvulus supinus
AND THEIR ANTIOXIDANT ACTIVITY
Abbes Benmerache, Djemaa Berrehal, Ahmed Kabouche,
and Zahia Kabouche*
UDC 547.972
Convolvulus is a fairly large genus with 250 species, almost cosmopolitan in distribution ꢀ1ꢁ. Various biological
activities such as anticancer [2], antinociceptive [3], antidiarrhea [4], and antifungal [5] have been reported for Convolvulus
species, which are characterized by the presence of phenolic compounds and alkaloids [6–9].
Algerian flora is represented by 17 species [10]. We have been interested in the phytochemical study and antioxidant
activity of the endemic species Convolvulus supinus Coss. & Kralik (Convolvulaceae).
Aerial parts (1.5 kg) of Convolvulus supinus were macerated in a methanolic solution (80%) at room temperature.
The extract was concentracted under low pressure, diluted with water, and filtered, then successively extracted with
dichloromethane, ethyl acetate, and n-butanol.
The butanolic extract (12 g) was column chromatographed on polyamid SC , eluting with toluene–methanol with
6
increasing polarity. Atotal of 103 fractions was obtained and combined into 19 main fractions (according to the number, color,
and R of the sports). Fraction F-9 was separated by column chromatography on silica gel and eluted with an isocratic system
f
of EtOAc–MeOH–H O (10:1:0.5) to afford compounds 1 and 2. Fraction F-14 was subjected to column chromatography on
2
silica gel and eluted with an isocratic system of EtOAc–MeOH–H O (10:1:1.5) to yield compound 3. These compounds were
2
1
13
identified by the use of spectral methods: UV, H NMR, and C NMR in addition to acid hydrolysis.
Acid Hydrolysis. The pure compounds were treated with 2M HCl at 100ꢂC for 1 h. The hydrolysates were extracted
with EtOAc, and the aglycones were identified by their UV spectra in methanol and by comparison of their R with authentic
f
samples. Sugars were identified in the aqueous residue by comparison with authentic samples on silica gel TLC impregnated
with 0.2 M NaH PO4, solvent Me CO–H O (9:1), revealed with aniline malonate.
2
2
2
Antioxidant Activity. The radical scavenging activity of the n-butanolic extract of Convolvulus supinus was measured
by the slightly modified method of Hatano [11]. One milliliter of a 0.2 mM DPPH methanol solution was added to 4 mL of
various concentrations of the extract in methanol. The mixture was shaken vigorously and left to stand at room temperature.
After 30 min, the absorbance of the solution was measured at 517 nm and the antioxidant activity calculated using the following
equation: Scavenging capacity % = 100 – [(Ab of sample – Ab of blank) ꢃ 100/Ab of control]. Methanol (1 mL) plus plant
extract solution (4 mL) were used as a blank, while DPPH solution plus methanol was used as a negative control. The positive
control was DPPH solution plus 1 mM rutin. The extract concentration providing 50% inhibition (IC ) was calculated from
5
0
the plot of inhibition percentage against extract concentration.
Compound 1. C H O , mp 272ꢂC. UV (MeOH, ꢄ , nm): 266, 350; + NaOH: 274, 325, 400; + AlCl : 275, 398;
2
1
20 11
max
3
1
+
AlCl /HCl: 275, 398; NaOAc: 275, 375; + H BO : 266, 357. H NMR (400 MHz, CD OD, ꢅ, ppm, J/Hz): 8.10 (2H, d, J = 9.0,
3 3 3 3
H-6ꢆ, H-2ꢆ), 6.90 (2H, d, J = 9.0, H-5ꢆ, H-3ꢆ), 6.43 (1H, d, J = 2.5, H-8), 6.22 (1H, d, J = 2.5, H-6), 5.25 (1H, d, J = 7.5, Glc H-1ꢆꢆ),
13
3
.20–4.00 (sugar protons). C NMR (100 MHz, CD OD, ꢅ, ppm): 177.0 (C-4), 165 (C-7), 161.5 (C-5), 160 (C-4ꢆ), 157.5 (C-2),
3
1
57 (C-9), 134 (C-3), 130.5 (C-2ꢆ, 6ꢆ), 121.5 (C-1ꢆ), 115 (C-3ꢆ, 5ꢆ), 104 (C-10), 98.50 (C-6), 93.50 (C-8), 102.50 (C-1ꢆꢆ), 76.7
(
C-5ꢆꢆ), 76.4 (C-3ꢆꢆ), 74.5 (C-2ꢆꢆ), 70.0 (C-4ꢆꢆ), 61.50 (C-6ꢆꢆ). Acid hydrolysis of compound 1 produced kaempferol and glucose.
This compound was characterized as kaempferol 3-O-ꢇ-D-glucoside [12, 13].
Compound 2. C H O , mp 272ꢂC. UV (MeOH, ꢄ , nm): 267, 351; + NaOH: 275, 325, 401; + AlCl : 273, 398;
2
7
30 15
max
3
1
+
AlCl /HCl: 274, 398; NaOAc: 273, 371; + H BO : 267, 351. H NMR (400 MHz, CD OD, ꢅ, ppm, J/Hz): 8.10 (2H, d, J = 8.9,
3 3 3 3
H-6ꢆ, 2ꢆ), 6.90 (2H, d, J = 8.9, H-5ꢆ, 3ꢆ), 6.43 (1H, d, J = 2.0, H-8), 6.22 (1H, d, J = 2.0, H-6), 5.20 (1H, d, J = 7.5, Glc H-1ꢆꢆ),
University of Constantine 1, Department of Chemistry, Laboratory of Therapeutic Substances, 25000, Constantine,
Algeria, e-mail: zahiakabouche@gmail.com. Published in Khimiya Prirodnykh Soedinenii, No. 5, September–October, 2013,
pp. 802–803. Original article submitted May 26, 2012.
0
936
0009-3130/13/4905-0936 2013 Springer Science+Business Media New York

4
.50 (1H, d, J = 1.5, Rha H-1ꢆꢆꢆ), 1.15 (3H, d, J = 6.2, Rha H-6ꢆꢆꢆ), 3.20–4.00 (sugar protons). 13C NMR (100 MHz, CD OD,
3
ꢅ, ppm): 176.5 (C-4), 164.5 (C-7), 161.5 (C-5), 160.0 (C-4ꢆ), 158.0 (C-2), 157.0 (C-9), 134.0 (C-3), 131.5 (C-2ꢆ, 6ꢆ), 121.5 (C-
1
6
ꢆ), 114.5 (C-3ꢆ, 5ꢆ), 104.5 (C-10), 99.0 (C-6), 93.5 (C-8), 103.5 (C-1ꢆꢆ), 76.6 (C-3ꢆꢆ), 75.8 (C-5ꢆꢆ), 74.5 (C-2ꢆꢆ), 70.1 (C-4ꢆꢆ),
7.25 (C-6ꢆꢆ), 101.0 (C-1ꢆꢆꢆ), 72.5 (C-4ꢆꢆꢆ), 71.0 (C-2ꢆꢆꢆ), 70.7 (C-3ꢆꢆꢆ), 68.25 (C-5ꢆꢆꢆ), 16.0 (C-6ꢆꢆꢆ). HMBC experiment established
a correlation between C-6ꢆꢆ at ꢅ 67.25 with H-1ꢆꢆꢆ at ꢅ 4.50 which permitted the characterization of compound 2 as kaempferol
3
-O-[ꢈ-L-rhamnosyl(1ꢉ6)-O-ꢇ-D-glucoside] [12, 13].
Acid hydrolysis of compound 2 produced kaempferol and glucose + rhamnose, confirming the nature of the two sugars.
Compound 3. C H O , mp 272ꢂC. UV (MeOH, ꢄ , nm): 266, 352; + NaOH: 275, 325, 400; + AlCl : 273, 398;
2
7
30 16
max
1
3
+
AlCl /HCl: 274, 398; NaOAc: 274, 377; + H BO : 269, 357. H NMR (400 MHz, DMSO-d , ꢅ, ppm, J/Hz): 8.10 (2H, d,
3
3
3
6
J = 8.4, H-6ꢆ, 2ꢆ), 6.75 (2H, d, J = 8.4, H-5ꢆ, 3ꢆ), 6.35 (1H, d, J = 1.1, H-8), 6.15 (1H, d, J = 1.1, H-6), 5.20 (1H, d, J = 6.1, Glc H-1ꢆꢆ),
1
3
4
.50 (1H, d, J = 7.5, Glc H-1ꢆꢆꢆ), 3.20–4.00 (sugar protons). C NMR (100 MHz, DMSO-d , ꢅ, ppm): 177.5 (C-4), 164.0
6
(
(
(
C-7), 161.2 (C-5), 160.5 (C-4ꢆ), 159.0 (C-2), 157.5 (C-9), 132.0 (C-3), 131.7 (C-2ꢆ, 6ꢆ), 122.5 (C-1ꢆ), 114.2 (C-3ꢆ, 5ꢆ), 105.0
C-10), 99.0 (C-6), 93.5 (C-8), 101.5 (C-1ꢆꢆ), 77.15 (C-3ꢆꢆ), 77.15 (C-5ꢆꢆ), 72.5 (C-2ꢆꢆ), 72.23 (C-4ꢆꢆ), 63.0 (C-6ꢆꢆ), 106.90
C-1ꢆꢆꢆ), 77.2 (C-3ꢆꢆꢆ), 77.1 (C-5ꢆꢆꢆ), 74.4 (C-2ꢆꢆꢆ), 67.0 (C-4ꢆꢆꢆ), 60.6 (C-6ꢆꢆꢆ). An HMBC experiment established a correlation
between C-6ꢆꢆ at ꢅ 63.0 with H-1ꢆꢆꢆ at ꢅ 7.50, which permitted the characterization of compound 3 as kaempferol 3-O-[ꢇ-D-
glucosyl(1ꢉ6)-O-ꢇ-D-glucoside] [14].
Acid hydrolysis of compound 3 produced kaempferol and glucose, confirming the nature of the sugar.
The three flavonol glycosides are reported for the first time from the species C. supinus. Compound 1 has been
reported from the single species C. arvensis [15], while compounds 2 and 3 are new for the genus Convolvulus.
The butanolic extract of Convolvulus supinus Coss. & Kralik exhibited good antioxidant activity (IC50 = 3.3 ꢊ 0.2 ꢋg/mL)
compared with the reference (rutin IC50 = 3.01 ꢊ 0.2 ꢋg/mL).
ACKNOWLEDGMENT
The authors thank the ANDRS and DGRSDT (MESRS), Algeria for financial support.
REFERENCES
1
2
.
.
A. Benmerache, D. Berrehal, A. Kabouche, Z. Semra, O. Thomas, R. Touzani, and Z. Kabouche, Pharm. Letter,
, 371 (2013).
X. L. Meng, N. H. Riordan, J. J. Casciari, Y. Zhu, J. Zhong, M. J. Gonzalez, J. R. Miranda-Massari,
5
and H. D. Riordan, P.R. Health Sci., 21, 323 (2002).
3
4
5
6
.
.
.
.
A. H. Atta and K. Abo El-Sood, J. Ethnopharmacol., 95, 235 (2004).
Attia H. Atta and Samar M. Mouneir, J. Ethnopharmacol., 92, 303 (2004).
M. H. Moubasher, Microbiology, 49, 128 (2000).
J. S. Kristina, M. Petra, K. Macki, S. Karsten, J. Jasmin, W. Ludger, and E. Eckart, Phytochemistry, 49,
1
449 (1996).
7
8
9
.
.
.
A. M. Gapparov, N. A. Razzakov, and S. F. Aripova, Chem. Nat. Compd., 43, 291 (2007).
N. A. Razzakov and S. F. Aripova, Chem. Nat. Compd., 40, 54 (2004).
G. T. Fred, R. S. Frank, S. Partricia, P. K. Anthony, and T. D. Josie, Phytochemistry, 39, 301 (1995).
P. Quezel and S. Santa, Nouvelle Flore de lꢆAlgerie et des Regions Desertiques Meridionales, Tome II,
Editions CNRS, Paris, 1963.
1
0.
11.
12.
13.
14.
15.
T. Hatano, H. Kagawa, T. Yasuhara, and T. Okuda, Chem. Pharm. Bull., 36, 2090 (1988).
A. Nawal, P. Shagufta, F. Itrat, N. Muhammad, and H. Ajaz, Molecules, 16, 10214 (2011).
A. M. Youssef Moustafa, A. I. Khodair, and A. S. Mahmoud, Pharm. Biol., 47, 539 (2009).
M. H. Hing, Y. C. Ruo, K. L. Lai, L. C. Franky, H. Yu, and C. Zhen-Yu, Biomed. Pharmacother., 56, 289 (2002).
M. Ruben Garcia, G. Silvia Erazo, and C. Pena Raul, Biochem. Syst. Ecol., 23, 571 (1995).
937