A procedure for the UV detection of hydroxyl and methoxyl groups at C6 in flavones and 3-O-substituted flavonols

Chemical constituents from Astragalus annularis Forssk. and A. trimestris L., Fabaceae

“…Both EI-MS and 13 C-NMR (Table 3) suggested the molecular formula C 16 H 12 O 6 indicating a flavone with one methoxyl and three hydroxyl groups. The two 1 H-NMR singlets (Table 2) at δ 6.53, 6.58 assigned for H-3 and H-8 (Feranandez et al, 1989;Gonzalez et al, 1985), respectively, the UV spectra of 4 with different shift reagents (Mears & Mabry, 1972), as well as the MS fragment at m\z 182 indicated free hydroxyl groups at C-5 and C-6 and a methoxyl group at C-7. The UV spectra indicated a free hydroxyl group at C-4' (Mabry et al, 1970;Asaad, 2002) which was further supported by the presence of two doublets at δ H 6.92 and δ H 7.85 (J=7.2 Hz, 2H each).…”

New Flavonol Acetates from the Frond Exudate of the Fern Notholaena aschenborniana

“…The PMR-spectrum of NAS-5 exhibits the follow ing signals (100 MHz, DM SO /TM S; < 3 ppm): 7.50 (2H, m; H-2' and H -6'), 6.96 (1H, d, 7 = 8.5 Hz; H-5'), 6.66 (1H, s; H-6), 3.90 (3H, s; O C H 3), 3.82 (6H, s; 2 O CH3), 2.37 (3H, s; -C O -C H 3). These data confirm the presence of 3 methoxyls and of 4 aro matic protons as well as the presence of an ace tyl group.…”

“…This suggests that it is located at the A-ring in o-position to OMe-7. Due to the UV-spectral data (c .f [6,7]) and also on the base of biochemical relations to NAS-1 and NAS-2 and to NG-1 and NG-2, this pro ton can be located at C-6, the esterified O H -group being ascribed to C-8. The flavonol NAS-4 thus is 5-hydroxy-3,7,2',3',4'-pentamethoxy-8-acetoxyflavone.…”

“…'H -N M R (100 MHz, D M SO -d6/ TMS; < 5 ppm) 7.18 (1H, d, J = 8.5 Hz; H-6'). 6.92 (1H, d, J = 8.5 Hz; H-5'), 6.68 ( 1H, s; H -6), 3.88 (6H, s; 2 OCH3), 3.80 (6H, s; 2 O C H 3), 3.68 (3H, s; 1 OCH3), 2.24 (3H, s; -CO -CH 3). These data confirm the existence of 5 methoxyl groups, of the acetoxy group, and of three arom atic protons.…”

Minor Phenolic Compounds from Teucrium hyrcanicum

“…51, 4.32, 4.38, 4.45). Mass spectrum (EI, 70 eV, m/z, I rel , %): 300 (100) [M] + .Comparison of TLC using system 1 found that 1 is colored brown by aqueous FeCl 3 (9%) and has a chromatographic mobility between those of cirsiliol and pedalitin.The UV spectrum of 1 with ionizing and complexing reagents according to the literature [5]: (+MeONa) 231, 253 sh, 314 sh, 375 (log J demonstrated the presence of 4′-OH, 5-OH, and 6-OH groups [6,7] in addition to a substituted hydroxyl on C-7.The mass spectrum of 1 contains fragments with m/z 182 (4) (ring A), 121 (6), 119 (12), and 118 (6) (ring B). The weakness of the quinoid ions with m/z 181 (3), 167 (3), 153 (5.5), 152 (9), 139 (9), and especially the ions for [M -CH 3 ] + with m/z 285 (1) and [M -CH 3 CO] + with m/z 257 (7) and the corresponding ions for ring A demonstrate the important difference of a flavone with a 6-OCH 3 (hypsidulin) and a 3-OCH 3 and 8-OCH 3 from that with a 7-OCH 3 [8] and confirm that the structure of 1 is 5,6,4′-trihydroxy-7-methoxyflavone (7-methylscutellarein).…”