Chemical constituents from the aerial parts of Sophora mollis

Abstract

Sophora mollis (Royle) Baker is a perennial shrub and is widely distributed in southwestern China, Pakistan, India, Iran, Afghanistan, and Nepal [1]. In previous studies, quinolizidine alkaloids and flavonoids have been isolated from this plant [2–4]. In our investigation into the chemical constituents of S. mollis, eight compounds were isolated and identified from the aerial parts of S. mollis for the first time. The aerial parts of S. mollis were collected during July 2006 from Chitral in the north of Pakistan. Taxonomic identification was done by Naveed Ahmad, Department of Botany, University of Peshawar, Pakistan. A voucher specimen (JA-08-C) was deposited in the herbarium at the Department of Botany, University of Peshawar, Peshawar, Pakistan. Air dried, powdered aerial parts (2.9 kg) were extracted with n-hexane for 8 days using a Soxhlet extractor. The n-hexane extract was separated from the plant residue by decantation and filtration. The filtered n-hexane extract was left overnight. A pale yellow solid precipitated (MRK-2, 13 g) and was filtered out. The filtrate was concentrated under vacuum to obtain a residue (MRK-1, 51.9 g). The plant residue was further extracted with acetone using a Soxhlet extractor for one week. The acetonic extract was concentrated under reduced pressure by a vacuum rotary evaporator, which afforded a residue (MRK-3, 65 g). The MRK-3 fraction was subjected to column chromatography on silica gel eluted with petroleum ether– acetone (30:1, 15:1, 8:1, 4:1, 2:1, 1:1, 0:1) to give seven subfractions, A-G. Fraction B was then chromatographed on silica gel using petroleum ether with increasing amounts of EtOAc as eluent to give compounds 1, 2, 5, and 6. Fraction C was rechromatographed on a silica gel column using a CHCl3–EtOAc gradient solvent system to afford compound 7. Fraction D was chromatographed on silica gel using CHCl3 with increasing amounts of acetone as eluent to give compound 3. Fraction E was chromatographed on a silica gel column using a CHCl3–acetone gradient solvent system to afford compound 4. Similarly, fraction F was chromatographed on silica gel using CHCl3 with increasing amounts of acetone as eluent to give compound 8. The structures of all compounds were determined by spectroscopic evidence, including EI-MS, 1D NMR, and 2D NMR. The spectroscopic data of all compounds were in good agreement with the literature data. (E)-Phytyl Epoxide (1). C20H40O2, colorless oil. EI-MS m/z (%): 312 [M]+ (1), 284 (1), 269 (1), 256 (1), 250 (1), 157 (1), 43 (100). 1H NMR (400 MHz, CDCl3, δ, ppm, J/Hz): 3.85 (1H, dd, J = 12.0, 4.3, H-1a), 3.68 (1H, dd, J = 12.0, 6.6, H-1b), 2.99 (1H, dd, J = 6.6, 4.3, H-2), 1.29 (3H, s, H-17), 0.86 (6H, d, J = 6.8, H-18, H-19), 0.87 (6H, d, J = 6.8, H-16, H-20). 13C NMR (100 MHz, CDCl3, δ, ppm): 61.3 (C-1), 63.1 (C-2), 61.7 (C-3), 39.3 (C-4), 24.7 (C-5), 36.9 (C-6), 32.7 (C-7), 37.4 (C-8), 22.5 (C-9), 37.2 (C-10), 32.7 (C-11), 37.2 (C-12), 24.4 (C-13), 38.8 (C-14), 24.7 (C-15), 22.7 (C-16), 16.7 (C-17), 19.6 (C-18), 19.7 (C-19), 22.6 (C-20) [5].