A new isoflavanone from the trunk of Horsfieldia pandurifolia

A new isoflavanone, 2,2′-epoxy-4′-methoxy-3,7-dihydroxyisoflavanone (1), and a new natural coumaranone, 2-hyroxy-2-(4′-methoxybenzyl)-6-methoxy-3-coumaranone (2), along with 26 known compounds, were first isolated from the trunk of Horsfieldia pandurifolia. Their structures were elucidated by the means of spectroscopic analysis. Compound 1 was assessed for its cytotoxicity against five human tumour lines (HL-60, SMMC-7721, A-549, MCF-7 and SW-480), and the result showed that it has no activity.


Introduction
The genus Horsfieldia belongs to the family Myristicaceae and comprises about 90 species distributed in South Asia from India to Papua New Guinea, among which five are growing in China (Jiang & Li 1979). Literature survey showed that most phytochemical investigations were focused on the seeds of those species, as the seeds of Horsfieldia glabra, Horsfieldia pandurifolia and Horsfieldia tetratepala are good resources for industrial oil (Xu et al. 2012). Previous phytochemical investigation of non-oil constituents on the genus led to the isolation of arylalkanones, lignans, chromones, flavones, alkaloids and steroids, and some of the compounds demonstrated antimalarial and cytotoxic activities Tillekeratne et al. 1982;Pinto et al. 1988;Jossang et al. 1991;Gonzalez et al. 2002;Al-Mekhlafi et al. 2013;Lu et al. 2014). H. pandurifolia is endemic to the subtropical area of Yunnan, China. However, its non-oil chemical constituents have never been reported up to date. As part of a research of structurally unique and biologically active compounds from medicinal plants of Yunnan, China, a new isoflavanone, 2,2 0 -epoxy-4 0 -methoxy-3,7-dihydroxyisoflavanone (1), and a new natural coumaranone, 2-hyroxy-2-(4 0 -methoxybenzyl)-6-methoxy-3-coumaranone (2), as well as 26 known compounds including 21 flavonoids from the trunk of H. pandurifolia (Figure 1) have been isolated and identified. Compound 2 has been synthesised (Chopin 1965), but it is new from natural sources.
The new compound 1 was assessed for its cytotoxicity against five human tumour lines (promyelocytic leukaemia cell line HL-60, liver cancer cell line SMMC-7721, lung cancer cell line A-549, breast adenocarcinoma cell line MCF-7 and colon carcinoma cancer cell line SW-480), but it showed no activity.

Experimental 3.1. Apparatus and reagents
Optical rotations were measured with a JASCO DIP-370 digital polarimeter (JASCO Corporation, Tokyo, Japan). A BioRad FtS-135 spectrophotometer was used for scanning IR spectroscopy with KBr pellets (Bio-Rad Corporation, Hercules, CA, USA). 1D and 2D NMR spectra were recorded on a Bruker DRX-AV-500 spectrometer (Bruker BioSpin Group, Rheinstetten, Germany) with TMS as internal standard. Unless otherwise specified, chemical shifts (d) are expressed in ppm with reference to the solvent signals. MS data were measured on a VG Auto Spec-3000 spectrometer (VG PRIMA, Birmingham, England). Column chromatography was performed on silica gel (80 -100 and 200 -300 mesh) (Qingdao Marine Chemical Factory, Qingdao, China), and Sephadex LH-20 (20 -80 mm; Pharmacia Fine Chemical Co. Ltd., Uppsala, Sweden). Fractions were monitored by TLC (Si gel GF 254 ) (Qingdao Marine Chemical Factory, Qingdao, China) and spots were visualised by heating silica gel plates sprayed with 10% H 2 SO 4 in EtOH. Solvents were of industrial purity and distilled prior to use.

Plant material
The trunk of H. pandurifolia was collected in January 2007 from Mengla of Yunnan, China, and identified by Mr Chao-Zhong Peng, a botanist of Yunnan Branch, Institute of Medicinal Plant Development, Chinese Academy of Medical Sciences. A voucher specimen (No. 070120) has been deposited at the School of Chemistry and Chemical Engineering, Yunnan Normal University.

Extraction and isolation
The trunkof H. pandurifolia (8.5 kg) was extracted with MeOH (30 L) for four times at room temperature. Evaporation of the solvent under reduced pressure gave an extract (280 g), which was partitioned between EtOAc and H 2 O. The EtOAc-soluble portion (105 g) was subjected to a silica gel CC (450 g, 100200 mesh) using a gradient of petroleum ether -EtOAc (50:1 to 0:1) to yield 11 fractions (A -K).

Supplementary material
Supplementary material relating to this article is available online at http://dx.doi.org/10.1080/ 14786419.2015.1043554.