Flavonoids from Sophora griffithii and Goebelia pachycarpa

Abstract

Herein we communicate results from a study of flavonoids from Sophora griffithii Stocks and Goebelia pachycarpa Schrenk.Leaves of S. griffithii act as an expectorant. The total flavonoids exhibit antibacterial activity. Apigenin, isoquercitrin, and quercetin glucoarabinoside have been isolated from the aerial part [1]. Flavonoids from the roots of this plant have not been previously studied.Ground air-dried roots of S. griffithii were collected near Tashkumir (Republic of Kyrgyzstan) and extracted at room temperature five times with ethanol (85%). The condensed extracts were diluted with water and worked up successively with CHCl 3 and ethylacetate. The CHCl 3 fraction was evaporated and chromatographed over a column of silica gel with gradient elution by CHCl 3 :hexane (95:5-50:50). Elution of the column with an 85:15 ratio of solvents gave 1.The isolated compounds were identified using UV, PMR, and mass spectra, chemical transformations, and direct comparison with authentic specimens.Inermin (1), C 16 H 12 O 5 , mp 180-181°C (benzene), [α] D -211° (c 0.4, ethanol). UV spectrum (EtOH, λ max , nm, log ε): 282 (3.53), 287 (3.59), 3.11 (3.78), characteristic of pterocarpanes [2]. The PMR spectrum (100 MHz, C 5 D 5 N, δ, ppm, J/Hz) exhibits signals at 3.42-3.92 (1H, m, H-6), 4.18 (1H, m, H-6a), 5.50 (1H, d, J = 6.0, H-11a), 5.85 (2H, d, J = 1.5, -OCH 2 O-), 6.60 (1H, s, H-10), 6.80 (2H, br.s, H-4, H-7), 6.86 (1H, dd, J = 8.5, 2.0, H-2), 7.50 (1H, d, J = 8.5, H-1). The mass spectrum of 1 exhibited a base peak for the molecular ion with m/z 284 and peaks for ions with m/z 147 and 175 due to ions a and b, respectively [2].Thus, 1 is 6a(R),11a(R)-3-hydroxy-8,9-methylenedioxypterocarpane (inermin) [2, 3]. Inermin was isolated from S. griffithii for the first time.The alkaloid pachycarpine was isolated from Goebelia pachycarpa. The aerial part of this plant is used in folk medicine for eczema, as an analgesic, and as a spasmolytic agent [4].Quercetin, kaempferol, and genistein and its xyloglucoside have been isolated previously from the aerial part of this plant [1].Chromatography over a silica-gel column using gradient elution by CHCl 3 :CH 3 OH isolated from the alcohol extract of roots of Goebelia pachycarpa flavonoid 2.Vexibinol (2), C 25 H 28 O 6 , mp 170-172°C, [α] D -36.5° (c 1.0, CH 3 OH). UV spectrum (EtOH, λ max , nm, log ε): 293 (4.23), 340 sh (3.69), characterisitc of flavanones [5]. The flavanone nature of 2 was confirmed by the PMR spectrum (100 MHz, DMSO-d 6 , δ, ppm, J/Hz), which exhibited signals at 5.52 (1H, dd, J = 13.0, 3.0, H-2), 2.56 (1H, q, J = 17.4, 3.0, H-3 ax ), and 3.12 (1H, q, J = 17.4, 13.0, H-3 eq ). The spectrum also contained signals for protons of a lavandulyl group, aromatic protons of a 5,7,8,2′,4′-substituted flavanone, and a 5-OH chelate. The mass spectrum of 2 contained peaks for ions (m/z) 424 [M] + , 406, 391, 301, 284, 283 (100%), 219, 165, 136, 124, etc.Thus, spectral data identified 2 as 5,7,2′,4′-tetrahydroxy-8-lavandulylflavanone or sophoroflavanone G (vexibinol) [6,7].Vexibino...