Dihydropyranoflavones from Pongamia pinnata

Das cascas do caule de Pongamia pinnata foram isolados dois novos compostos, 3-metoxi(3′′,4′′-diidro3′′-hidroxi-4′′-acetoxi)-2′′,2′′-dimetilpirano-(7,8:5′′,6′′)-flavona e 3-metoxi-(3′′,4′′diidro-4′′hidroxi-3′′-acetoxi)-2′′,2′′-dimetilpirano-(7,8:5′′,6′′)-flavona, juntamente com seis compostos conhecidos, óxido de cariofileno, obovatachalcona, 8-hidroxi-6-metoxi-3-pentil-1Hisocromeno-1-ona, 6,7,2,2-dimetilcromono-8,γ,γ-dimetilalilflavonona, isolonchocarpin, ovaliflavanona A. Suas estruturas foram determinadas a partir da interpretação de dados espectroscópicos.


Introduction
Pongamia pinnata (Linn) Pierre (Leguminosae, Papilionaceac; synonym, Pongamia glabra Vent), the only one species of genus Pongamia, is a medium sized glabrous tree, grows in the littoral regions of South Eastern Asia and Australia.All parts of the plant have been used as crude drug for the treatment of tumors, piles, skin diseases, wounds and ulcers. 1 Extracts of the plant possess significant anti-diarrhoeal, anti-fungal, anti-plasmodial, antiulcerogenic, anti-inflammatory, and analgesic activities. 2 Previous phytochemical investigation of this plant indicated the presence of abounding prenylated flavonoids such as furanoflavones, furanoflavonols, chromenoflavones, furanochalcones, and pyranochalcones. 3In this paper, we reported the isolation and identification of two new flavones (1, 2) from the stem bark of Pongamia pinnata.
Compound 2, a white powder, gave a molecular ion [M + ] at m/z 410.13665 in the HREIMS, corresponding to the molecular formula C 23 H 22 O 7 (calc.410.13655).The NMR spectral data of 2 (Table 1) were closely comparable to those of compound 1, with the only difference being due to the position of the acetoxy group (δ H 2.13, 3H, s, δ C 170.5, δ C 21.3, OAc-3″) and hydroxyl group on the pyran ring.In HMBC spectra, the observed correlations from protons of Me 1 -2″ (δ H 1.41, 3H, s), Me 2 -2″ (δ H 1.35, 3H, s) to C-3″ (δ C 72.9), and from H-3″ (δ H 5.06, 1H, d, J 4.8 Hz) to the carbonyl of acetoxyl group suggested the acetoxy group to be located on C-3″ position.Further analysis of the NMR and MS spectra of compound 2 indicated the presence of the hydroxyl group at C-4″ position.The coupling constant J 3″, 4″ was 4.8 Hz and the chemical shift difference of gem-dimethyl signals was 0.06 ppm in 1 H NMR spectrum.This evidence suggested that the relative configuration of compound 2 was cis-form.

General
Optical rotation were measured with a Jasco 1020 polarimeter.NMR spectra were obtained on a Bruker AVANCE 500 spectrometer (500 MHz for 1 H NMR, 125 MHz for 13 C NMR).EIMS and HREIMS spectra were recorded on a Finnigan MAT TSQ 700 mass spectrometer.UV spectra were obtained in a Beckman DU-640 UV spectrophotometer.A Waters Nova-pack HR C18 column (19×300mm) was used for semipreparative HPLC, along with Waters 600E Multisolvent Delivery System and a Waters 996 Photodiode Array Detector.

Plant material
The material investigated were stem bark of Pongamia pinnata collected in October 2002 from Hainan Province, southern China.The material was identified by Professor Si Zhang, Guangdong Key Laboratory of Marine Materia Medica, South China Sea Institute of Oceanology, Chinese Academy of Sciences.A voucher specimen is deposited at the herbarium of the South China Sea Institute of Oceanology (No. GKLMMM005).

Table 1 .Table 1 .
1H,13C and selected HMBC NMR data for compounds 1 and 2 a a spectra recorded in DMSO-d 6 (500 MHz for 1 H, 125 MHz for 13 C); TMS was used as internal standard.Yin et al.J. Braz.Chem.Soc.