Corresponding Author:
S. Das
Sri Sai Aditya Institute of Pharmaceutical Sciences and Research, A. D. B. Road, Surampalem, Peddapuram-533 437
E-mail: [email protected]
Date of Submission 12 February 2014
Date of Revision 13 January 2015
Date of Acceptance 01 June 2015
Indian J Pharm Sci 2015;77(3):352-356  

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Abstract

Phytochemical evaluation of the chloroform extract of roots of Polygonum viscosum has yielded six compounds, stigmasterol, 7,4-dimethylquercetin, kaempferol, quercetin, myricetin and scutellarein. Among the six compounds isolated and characterized by chemical and spectral (UV, NMR and Mass) analysis in the present phytochemical evaluation, stigmasterol was not reported earlier from P. viscosum. The compounds, 7,4ʹ-dimethylquercetin, quercetin and scutellarein were reported from P. hydropiper. Kaempferol from P. amphibium, P. aviculare, P. convolvulus, P. hydropiper, P. lapathifolium and P. persicaria and myricetin from P. aviculare and P. lapathifolium were also reported earlier. This appers to be the first report of the occurrence of all the six compounds from P. viscosum.

Keywords

Polygonum viscosum, Polygonaceae, phytochemical evaluation, stigmasterol, 7,4−dimethylquercetin,kaempferol, quercetin, myricetin, scutellarein

Polygonum viscosum Buch-Ham. (Polygonaceae), common Bengali name ″Bishkatali″ is an annual odoriferous herb (50-90 cm) indigenous to Nepal and is widely distributed in Bangladesh, north-east India, China and Japan. The genus Polygonum is well-known for producing pharmacologically active substances and also for its use in Oriental traditional medicine systems. Ethanol extract of Polygonum viscosum is known to have antibacterial properties [1]. A flavonoid glycoside, quercetin- 3-O-(6″-feruloyl)-β-D-galactopyranoside from aerial parts of the plant was reported to have antiHIV1, anticholinergic, analgesic and CNS depressant activities and significant cytotoxicity against the ovarian cancer cell line (OVCAR-3). The sesquiterpenes from aerial parts, viscosumic acid and viscozulenic acid for antiinflammatory, analgesic and CNS depressant activities, viscoazucine for analgesic and CNS depressant activities, viscoazulone for antiinflammatory, antiHIV1 and CNS depressant activities and viscozulenic acid methyl ester, viscoazucinic acid and polygosumic acid for antibacterial acitivity against penicillin-resistant Escherichia coli and methicillin-resistant Staphylococcus aureus were reported [2,3].

The sequiterpenes, viscoazusone, viscoazulone, viscozulenic acid, viscozulenic acid methyl ester, viscoazucine, viscoazucinic acid, viscosumic acid and polygosumic acid and flavonoids, 3′,5-dihydroxy- 3,4′,5′,7-tetramethoxyflavone, 3′,5,7−trihydoxy−3,4′,5′- trimethoxyflavone, quercetin−3−O−(6″-caffeoyl)-β- D-galactopyranoside, quercetin−3−O−(6″-feruloyl)- β-D-galactopyranoside and quercetin−3−O−(6″- galloyl)-β-D-galactopyranoside were reported so far from the species P. viscosum [1-6]. As a part of the ongoing phytochemical and bioactivity studies on the Polygonum genus, the authors have reinvestigated its roots for its bioactive phytoconstituents.

Silica gel (Merck, Mumbai, India) 100-200 mesh for column chromatography and silica gel (SDFCL, Mumbai. India) 350 mesh for preparative TLC were used. Successive gradient elution was accomplished by the solvents, n-hexane, chloroform and methanol (Merck, Mumbai, India). Melting points were recorded on Cipla I-28 digital apparatus (Cipla, Mumbai, India). 1H NMR using DMSO-d6 (2, 3, 4, 5, 6) and 13C NMR using CDCl3 (1) were run on Bruker 400 MHz spectrometer (Bruker, Ettlingen, Germany). All the mass spectra were taken accurately under API-ES conditions using Agilent 1100 series LC/MS (Agilent 1100 series, Agilent Technologies Deutschland GmbH, Waldbronn, Germany).

The plant material Polygonum viscosum was collected from forest Pilak, India. Authentication of the plant specimen (SD001) was done at the Botanical Survey of India, Deccan Regional Centre, Hyderabad. A voucher specimen (SD001) was deposited at the Herbarium of the University College of Pharmaceutical Sciences, Andhra University, Visakhapatnam, India.

One kilogram of the dried root powder was extracted with CDCl3 (3×1.5 l) for 24 h at room temperature. TLC examination of the residue showed numbers of prominent spots (MeOH-CDCl3, 1:99). The pooled extract was concentrated under reduced pressure and yielded 14 g brown residue. The extract (12 g) was chromatographed over silica gel following gradient elution (each 200 ml fraction) technique successively using n-hexane, CDCl3 and MeOH. Fractions 43-51 (CDCl3-hexane, 25:75) obtained white amorphous powder which on repeated crystallisation from hexane afforded white needles of stigmasterol, mp 163-165°, identical with an authentic sample [7]. Fractions 124-127 (MeOH-CDCl3, 5:95) yielded dark yellow solids which on repeated crystallisation from a mixture of MeOH-CDCl3, 19:1 obtained 0.02 g of yellow crystals of 7,4′-dimethylquercetin, mp 238-240°, identical with an authentic sample [8]. Fractions 128-131 (MeOHCHCl 3, 5:95) yielded yellow solid which on repeated crystallisation from MeOH obtained 0.02 g yellow crystals of kaempferol, mp 275-277°, identical with an authentic sample [9]. Fractions 132-135 (MeOH-CDCl3, 10:90) yielded yellow amorphous mass which on recrystallisation from MeOH, afforded 0.02 g yellow needles of quercetin, mp 318-320°, identical with an authentic sample [9]. Fractions 139-142 (MeOH-CDCl3, 15:85) yielded another dark yellow solid which on repeated crystallisation from MeOH afforded 0.03 g yellow needles of myricetin, mp 357-359°, identical with an authentic sample [10]. Fractions 143-148 (MeOH-CDCl3, 20:80) yielded clump of yellow mass which on subsequent recrystallisation from MeOH, obtained 0.02 g pale yellow crystals of scutellarein, mp 327-329°, identical to an authentic sample [11].

Stigmasterol (1), mp 163-165°; molecular mass 412.3 requires positive API-ES, m/z (rel. int.): 413.3 [M+H]+ (15) (calcd. for C29H49O 413.37). Liebermann-Burchard?s test: A play of colours (pink to blue to green). The 13C NMR spectral data are summarized in Table 1. 7,4′-dimethylquercetin (2), mp 238-240°, molecular mass 330.07 requires positive API-ES, m/z (rel. int.): 331.1 [M+H]+ (100) (calcd. for C17H15O7 331.08) and 353.1 [M+Na]+ (20) (calcd. for C17H14O7Na 353.06). UV MeOH λmax nm: 250, 262 and 375; MeOH/AlCl3 264 and 432. The 1H NMR spectral data are represented in Table 1.

C/H 2c (δH) 3c (δH) 4c (δH ) 5c (δH) 6c (δH) 1b (δC) C 1b (δC)
1           37.30 9 50.21
2           31.72 10 36.55
3         6.73 (1H, s) 71.84 11 19.80
3-OH 9.76 (1H, s) 9.42 (1H, s) 9.40 (1H, s) 9.46 (1H, s)     12 39.83
4           47.74 13 45.92
5           140.81 14 56.82
5-OH 12.51 (1H, s) 12.48 (1H, s) 12.52 (1H, s) 12.61 (1H, s) 13.00 (1H, s)   15 24.32
6 6.32 (1H, d, 1.6) 6.18 (1H, d, 2) 6.19 (1H, d, 1.7) 6.18 (1H, d, 1.6)   121.71 16 29.25
6-OH         10.44 (1H, s)   17 56.13
7           36.16 18 11.98
7-OH   10.82 (1H, s) 10.90 (1H, s) 10.30 (1H, s) 10.35 (1H, s)   19 21.12
7-OMe 3.90 (6H, s)           20 42.36
8 6.78 (1H, d, 1.6) 6.44 (1H, d, 2) 6.41 (1H, d, 1.7) 6.38 (1H, d, 1.6) 6.67 (1H, s) 34.02 21 23.13
2' 7.79 (1H, d, 1.6) 8.04 (2H, d, 8.8) 7.73 (1H, d, 2.1) 7.29 (2H, s) 7.90 (2H, d, 8.8)   22 138.27
3′   6.93 (2H, d, 8.8)     6.91 (2H, d, 8.8)   23 129.34
3′-OH 9.53 (1H, s)   9.18 (1H, s) 8.40 (3H, s)     24 51.27
4′-OH   10.13 (1H, s) 9.61 (1H, s) 8.40 (3H, s) 8.69 s   25 31.95
4′-OMe 3.90 (6H, s)           26 18.80
5′ 6.90 (1H, d, 8) 6.93 (2H, d, 8.8) 6.94 (1H, d, 8.4)   6.91 (2H, d, 8.8)   27 19.40
5′-OH       8.40 (3H, s)     28 25.40
6′ 7.76 (1H, dd, 8, 1.6) 8.04 (2H, d, 8.8)  7.62 (1H, dd, 8.4, 2.1) 7.29 (2H, s) 7.90 (2H, d, 8.8)   29 11.87