Constituents of Apocynum venetum

Abstract

The perennial herbaceous plant Apocynum venetum L. (A. scabrum) (Apocyaceae) is broadly distributed in Central Asia, Iran, and China [1]. Flowers of A. venetum have long been used in folk and modern Chinese medicine as a medicinal tea. The plant extract increases blood pressure and exhibits hepatoprotective, hypolipidemic, hepatotropic, anti-oxidant, and antiviral properties [2]. We investigated flowers of A. venetum collected in Xinjiang Autonomous Region of the PRC. Ground air-dried raw material (5 kg) was extracted exhaustively with EtOH (70%) at room temperature. The solvent was vacuum distilled. The dry solid was worked up successively with petroleum ether (6 0.5 L), CHCl3 (6 0.5 L), EtOAc (10 0.5 L), and n-BuOH (10 0.5 L). The EtOAc extract (20 g) was chromatographed over a column (2.6 150 cm) of silica gel (550 g) with elution by CHCl3:MeOH (97:3, 95:5, 90:10, 85:15). Seven compounds, 1-7, were isolated. A comparison of spectral data (UV, IR, PMR, 13C NMR) with the literature and direct comparison with authentic samples identified the isolated compounds as -sitosterol (1) [3], salicylic acid (2), p-hydroxybenzoic acid (3), methyl-3,4dihydroxybenzoate (4), -sitosterol -D-glucopyranoside (5), kaempferol (6), and quercetin (7). Salicylic acid (2), C7H6O3 [4], white crystals, mp 159.5°C (EtOAc). IR spectrum (KBr, , cm–1): 3229, 2926, 2855, 1660, 1612, 1484, 1443, 1325, 1226, 1209, 1154, 750, 696. UV, PMR, and 13C NMR spectral data agreed with those for salicylic acid [4]. p-Hydroxybenzoic acid (3), C7H6O3 [4], white powder, mp 159.5°C (EtOAc). Methyl-3,4-dihydroxybenzoate (4), C8H8O4. PMR spectrum (600 MHz, DMSO-d6, , ppm, J/Hz, 0 = HMDS): 3.77 (3H, s, OCH3-8), 6.84 (1H, d, J = 7.8, H-5), 7.44 (2H, dd, J = 1.2, 7.2, H-6), 7.44 (1H, d, J = 1.2, H-2), 9.84 (s, OH), 12.49 (s, OH). 13C NMR spectrum (150 MHz, DMSO-d6, , ppm): 121.58 (C-1), 115.00 (C-2), 147.20 (C-3), 151.08 (C-4), 112.69 (C-5), 123.45 (C-6), 167.20 (C-7), 55.95 (C-8). -Sitosterol -D-glucopyranoside (5), C35H60O6, mp 275–277°C. PMR and 13C NMR spectral data of 5 agreed completely with those published [5]. Kaempferol (6), C15H10O6 [6], yellow crystals, mp 276–277°C (EtOAc). PMR and 13C NMR spectral data agreed with those published [6]. Quercetin (7), C15H10O7 [7], mp 305–307°C (EtOAc). Spectral data agreed with those published [7]. The listed compounds were isolated for the first time from A. venetum.