Flavonoids from the Aerial Part of Scutellaria intermedia

Abstract

Flavonoids of promising Scutellaria species were studied systematically in order to discover new available sources of biologically active compounds [1–4]. Plants of the genus Scutellaria L. are widely used in folk medicine. Their extracts and pure flavonoids possess antitumor, antiviral, hepatoprotective, antioxidant, anti-inflammatory, anticonvulsant, antibacterial, and antiviral properties [5–10]. The present research studied the aerial part of S. intermedia Popov [11] that was collected during flowering in the foothills of Pap District, Republic of Uzbekistan. Flavonoids from this plant have not been reported. Air-dried ground aerial plant parts (0.75 kg) were extracted (3 ) with refluxing EtOH (96%). The combined extract was evaporated in vacuo. The residue was diluted with H2O and extracted sequentially with petroleum ether, EtOAc, and n-BuOH to afford petroleum ether (5.6 g), EtOAc (17.8 g), and n-BuOH fractions (26.7 g). A part (13.0 g) of the EtOAc fraction was chromatographed over a column of silica gel (400 g) using a petroleum ether–EtOAc gradient. Separate fractions were rechromatographed over columns with silica gel and Sephadex LH-20 to isolate pure flavonoids 1 (75 mg), 2 (87), 3 (203), 4 (35), 5 (14), 6 (103), 7 (18), and 8 (27). The obtained flavonoids were identified using spectral data and comparisons with authentic samples. Chrysin (1), C15H10O4, mp 290–292 Ñ. ESI-MS, m/z 255.2 [M + H] +. UV spectrum ( max, nm): 270, 310 (sh). 1Í NMR spectrum (400 MHz, DMSO-d6, , ppm, J/Hz): 6.23 (1H, d, J = 2.0, H-6), 6.47 (1H, d, J = 2.0, H-8), 6.93 (1H, s, H-3), 7.51 (3H, m, H-3 , 4 , 5 ), 8.00 (2H, dd, J = 7.8, 2.0, H-2 , 6 ), 12.16 (1H, s, 5-OH) [2, 8]. Oroxylin A (2), Ñ16Í12Î5, mp 218–219 Ñ. ESI-MS, m/z 285.3 [M + H] +. UV spectrum ( max, nm): 249, 272, 321. 1Í NMR spectrum (400 MHz, DMSO-d6, , ppm, J/Hz): 4.05 (3H, s, OCH3), 6.63 (1H, s, H-3), 6.67 (1H, s, H-8), 7.58 (3H, m, H-3 , 4 , 5 ), 7.90 (2H, dd, J = 8.2, 2.0, H-2 , 6 ), 12.39 (1H, s, 5-OH) [1, 8]. 7-O-Methylnorwogonin (3), Ñ16Í12Î5, mp 143–145 Ñ. ESI-MS, m/z 285.3 [M + H] +. UV spectrum ( max, nm): 340, 275. 1Í NMR spectrum (400 MHz, DMSO-d6, , ppm, J/Hz): 3.91 (3H, s, OCH3), 6.77 (1H, s, H-6), 6.62 (1H s, H-3), 7.58 (3H, m, H-3 , 4 , 5 ), 8.03 (2H, dd, J = 8.8, 2.0, H-2 , 6 ), 11.98 (1H, s, 5-OH) [3]. 5,7,22-Trihydroxyflavone (4), C15H1005, mp 284 C. ESI-MS, m/z 271.2 [M + H] +. UV spectrum ( max, nm): 268, 342. 1Í NMR spectrum (400 MHz, DMSO-d6, , ppm, J/Hz): 6.18 (1H, d, J = 1.8, H-6), 6.44 (1H, d, J = 1.8, H-8), 6.95 (1H, m, H-5 ), 7.06 (1H, dd, J = 8.0, 1.8, H-3 ), 7.13 (1H, s, H-3), 7.38 (1H, m, H-4 ), 7.88 (1H, dd, J = 8.0, 1.8, H-6 ), 12.24 (1H, s, 5-OH). 13C NMR spectrum (100 MHz, DMSO-d6, , ppm): 94.5 (C-8), 99.6 (C-6), 103.6 (C-10), 109.3 (C-3), 117.4 (C-3 ), 117.6 (C-1 ), 119.1 (C-5 ), 128.8 (C-6 ), 133.0 (C-4 ), 158.0 (C-2 ), 158.3 (C-9), 161.6 (C-5), 161.8 (C-2), 166.3 (C-7), 182.5 (C-4) [5, 8]. 2(S)-5,7,22-Trihydroxyflavanone (5), C15H12O5, mp 201–203 Ñ. ESI-MS, m/z 273.2 [M + H] +. UV spectrum ( max, nm): 240, 288, 331. 1Í NMR spectrum (400 MHz, DMSO-d6, , ppm, J/Hz): 2.69 (1H, dd, J = 17.2, 3.2, H-3å), 3.21 (1H, dd, J = 17.2, 12.6, H-3a), 5.73 (1H, dd, J = 12.6, 3.2, H-2), 5.88 (1H, d, J = 2.3, H-6), 5.93 (1H, d, J = 2.3, H-8), 6.82 (1H, dd, J = 7.8, 7.6, H-5 ), 6.89 (1H, br.d, J = 7.8, Í-3 ), 7.19 (1H, dd, J = 7.8, 7.6, H-4 ), 7.41 (1H, d, J = 7.8, H-6 ), 12.05 (1H, s, 5-ÎÍ) [8, 12]. Scutevulin (5,7,22-trihydroxy-8-methoxyflavone, 6). C16H12O6, mp 277–278 C (dec.). ESI-MS, m/z 301.3 [M + H]+. UV spectrum ( max, nm): 263 (sh), 281, 330, 380 (sh). 1Í NMR spectrum (400 MHz, DMSO-d6, , ppm, J/Hz): 3.81 (3H, s, OCH3), 6.04 (1H, s H-6), 6.95 (1H, m, H-5 ), 7.01 (1H, dd, J = 8.0, 1.8, H-3 ), 7.08 (1H, s, H-3), 7.35 (1H, m,

DOI: 10.1007/s10600-017-2107-z

Cite this paper

@article{Karimov2017FlavonoidsFT, title={Flavonoids from the Aerial Part of Scutellaria intermedia}, author={Alexei Karimov and T. N. Slobodyanyuk and {\'E}. Kh. Botirov}, journal={Chemistry of Natural Compounds}, year={2017}, volume={53}, pages={745-746} }