A New 5(6→7)abeo-sterol from the twigs of Podocarpus fleuryi

Abstract A new 5(6→7)abeo-sterol with rarely reported [6–5-6–5]-fused rings, 3β,5β,6-trihydroxyl-B-norsitostane (1), along with 10 known compounds were isolated from the twigs of Podocarpus fleuryi. Their structures were elucidated by means of extensive spectroscopic analysis. Compound 1 was assessed for their cytotoxicity against five human tumour cell lines (HL-60, SMMC-7721, A-549, MCF-7 and SW-480), and the result showed that it had no activity.


Introduction
Podocarpus is a genus of the family Podocarpaceae, which contains about 100 different species grown in scattered parts of East Asia and in the southern hemisphere, with 13 species and 3 variants being endemic to China (Zheng & Fu 1978). This genus is important timber trees used by many communities in traditional medicine for the treatment of fever, asthma, cough, cholera, distemper, chest complaints and venereal diseases. Literature survey showed that an array of structurally interesting diterpenoids, including podolactones (nor-and bis-norditerpenoid dilactones), totarol, abietane and sempervirol diterpenoids, biflavonoids and flavonoids were isolated from plants of the genus Podocarpus (Xu & Fang 1989;Reynolds et al. 2006;Sato, Inaba et al. 2009;Sato, Sugawara et al. 2009;Faiella, Temraz, Siciliano et al 2012;Faiella, Temraz, Tommasi et al. 2012). These isolated constituents have been attracted a great deal of interest because of their wide range of biological activities, including antitumor, anti-inflammatory, antioxidant, antimicrobial and neuroprotective activities (Wang et al. 1997;Abdillahi et al. 2011;Bagla et al. 2014;Han et al. 2014;Addo et al. 2015;Gao et al. 2015;Novoa et al. 2015). Podocarpus fleuryi Hickel is distributed in China, Vietnam and Cambodia. Previously, diterpenoids, diterpene dilactones, biflavones and sterols have been isolated from P. fleuryi Xu et al. 1990;Xu & Fang 1991;Zhang et al. 2013). As parts of a research of structurally unique and biologically active compounds from medicinal plants of Yunnan, China, we investigated the twigs of P. fleuryi and isolated new 5(6→7)abeo-sterol with rarely reported [6-5-6-5]-fused rings, 3β, 5β, 6-trihydroxyl-B-norsitostane (1), as well as 10 known compounds (Figure 1). Reported herein are the isolation, structural elucidation and biological evaluation of these compounds.   Figure 1. structures of compounds 1-11.
Compound 1 was assessed for its' cytotoxicity against five human tumour cell lines (HL-60, SMMC-7721, A-549, MCF-7 and SW-480), but the result showed that it had no activity.

Apparatus and reagents
optical rotations were analysed on a Horiba SEAP-300 spectropolarimeter. IR was measured on a Perkin Elmer 241 polarimeter. MS data were determined on a VG Auto Spec-3000 spectrometer. NMR spectra were recorded on a Bruker dRX-AV-500 spectrometer at 500 MHz for 1 recorded with respect to TMS as an internal standard. Column chromatography (CC) was carried out on silica gel H (10-40 μm Qingdao Haiyang Chemical Factory, Qingdao, China), and Sephadex Pharmacia Fine Chemical Co Ltd,uppsala,Sweden). TLC was performed on silica gel GF 254 (Yantai Jiangyou Silica Gel Co Ltd, Yantai, China). Solvents were of industrial purity and distilled prior to use.

Plant material
The twigs of P. fleuryi were collected from Jinghong County of Yunnan Province, China in June, 2013 and identified by Mr Shuncheng Zhang, a botanist of Xishuangbanna Tropical Botanical Garden, Chinese Academy of Sciences, where a voucher specimen (No. 1306013) was deposited.

Disclosure statement
No potential conflict of interest was reported by the authors.

Funding
This work was supported by the Natural Science Foundation of China [grant number 31260085]; Yunnan Province of China for basic research in social development [grant number 2009CC018].