Iranian Journal of Pharmaceutical Research (2003) 249-250 Received: April 2003 Accepted: August 2003
Bahman Nickavar*a, Gholamreza Aminb, Nacim Mehreganb
aPharmaceutical Sciences Research Center, Shaheed Beheshti University of Medical Sciences, Tehran, Iran. bPharmacognosy Department, Faculty of Pharmacy, Tehran University of Medical Sciences, Tehran, Iran.
* Corresponding author E-mail: firstname.lastname@example.org
From the aerial parts of Tanacetum balsamita L. (Compositae) a flavonol aglycon was iso?lated using chromatographic techniques. The structure of this compound was determined using spectroscopic methods (UV, H-NMR and MS) as 3',4',5,7-Tetrahydroxy flavonol (Quercetin).
Keywords: Tanacetum balsamita L.; Compositae; Flavonol aglycon; Quercetin.
The genus Tanacetum (Compositae) consists of 26 species in Iran one of which is Tanacetum balsamita L. (1). T. balsamita, locally named Shahesparam, is an aromatic species which grows widely in Azerbaijan province. It has been used in Iranian folk medicine as a tranquilizer and cardiac tonic (2).
Some of the medicinal Tanacetum species such as T. parthenium and T. vulgare are known to be rich in flavonoids (3) but the flavonoid compositions of T. balsamita have not been the subject of much study (4, 5).
As part of our phytochemical research on pharmacologically active phenolic constituents of Iranian medicinal plants, the isolation and iden?tification of a flavonol aglycon (compound 1) from aerial parts of T. balsamita are de?scribed here.
Aerial parts of T. balsamita were collected from Tabriz in June 1999. Voucher specimens were deposited in the Herbarium of Department of Pharmacognosy, Faculty of Pharmacy, Tehran University of Medical Sciences.
Dried and ground plant materials (500g) were extracted with 90% MeOH and then concentrated in vacuo. The residue was diluted with water and extracted with n-Hexane, CH2Cl2, CHCl3 and EtOAc, successively. The EtOAc concentrated fraction (3.5g) was rich in flavonoids, so this fraction was chromatogra?phed on Silica gel PTLC with EtOAc-CH3COOH-HCOOH-H2O (100:11:11:26) as the best developing solvent and AlCl3 (5%) in MeOH under UV 366nm as visualizer. Finally, the most abundant constituent (compound 1, Rf=0.48, 15mg) (Figure 1) was isolated as pale yellow amorphous powder. The structure of this compound was established according to combined spectra data.
Figure 1. Compound 1 (3',4',5,7-Tetrahydroxy flavonol)
UV λmax (in MeOH): 260, 275sh, 380nm; + AlCl3: 265, 455nm; + AlCl3 + HCl: 265, 425nm; + NaOAc: 275, 380nm (degradation); + NaOAc + H3BO3: 260, 395nm; + NaOMe: rapid degradation.
H-NMR (400MHz, in DMSO-d6): δ 7.78 (1H, d, J=1.8Hz, H-2'), 7.65 (1H, dd, J=9, 1.8Hz, H-6'), 6.95 (1H, d, J=9Hz, H-5'), 6.41 (1H, d, J=2Hz, H-8), 6.26 (1H, d, J=2Hz, H-6).
EI-MS 70eV, m/z: 302 (M+, 100%), 301 (46%), 285 (4%), 284 (3%), 274 (6%), 273 (9%), 153 (5%), 152 (10%), 150 (4%), 137 (6%), 136 (17%).
Results and Discussion
Compound 1 developed a magenta color with Mg/HCl and exhibited UV absorption bands of flavonoids. The UV spectrum of the compound in MeOH showed two major absorption bands at 260nm (band II) and 380nm (band I) which are typical for flavonols. The presence of a shoulder in band ΙI (275nm) was an evidence of the 3',4'-ortho-dihydroxy system. Also, this system in the B-ring of the compound was indicated by the hypsochromic shift (-30nm, band I) by the AlCl3/HCl as compared to the band position in AlCl3 and by the bathochromic shift (+15 nm, band I) in NaOAc/H3BO3. The presence of a free hydroxyl group at 5 or 3 position and/or both of them was exhibited by the bathochromic shift (+75nm, band I) in AlCl3. The bathochromic shift (+15nm, band II) soon after the addition of NaOAc showed a free 7-OH group. The UV spectrum rapid degradation after the addition of NaOMe was an evidence of the presence of free hydroxyl groups at 3,3' and 4' positions (6).
The H-NMR spectrum also confirmed flavonol structure and displayed the presence of H-6, H-8, H-2', H-5' and H-6' protons. The PMR spectrum of the compound in DMSO-d6 showed two distinctive resonance groups. It displayed two doublets at δ 7.78 (1H, J=1.8Hz) and δ 6.95 (1H, J=9Hz) and one doublet of doublets at δ 7.65 (1H, J=9, 1.8Hz), characteristic of a 1,2,4-trisubstituted benzene ring (the ABC system with ortho and metha coupling, the B-ring of the flavonol) and two doublets at δ 6.41 (1H, J=2Hz) and δ 6.26 (1H, J=2Hz), characteristic of a 1,2,3,5-tetrasubstituted benzene ring (the AB system with meta coupling, the A-ring of the flavonol). The combination of the substitution patterns of the A and B rings suggested that the compound could be 3',4',5,7-Tetrahydroxy flavonol (6, 7).
The EI-MS spectrum of the compound was in agreement with the assigned structure. It revealed the empirical formula C15H10O7 with the molecular ion peak at m/z 302 (M+, base peak) and ion peaks at m/z 153 (A1+H)+ and m/z 150 (B1)+ due to the retro-Diel's-Alder type fragmentation and fragment m/z 137 (B2)+ (Figure 2) (6).?
The UV, H-NMR and EI-MS data led to the identification of the compound 1 as 3',4',5,7-Tetrahydroxy flavonol or Quercetin (Figure 1).
Figure 2. Fragments (A1+H)+, (B1)+ and (B2)+
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