Guaianolides and elemanolides from Vernonia anthelmintica Li Zhang a , Yong-Liang Shao a , Lei Hua b , Ya Li a , Syed Hamid Hussain c , Mohammad Arfan c , Kun Gao a, * a State Key Laboratory of Applied Organic Chemistry, College of Chemistry and Chemical Engineering, Lanzhou University, Lanzhou 730000, PR China b Technology Center of Gansu Tobacco Industrial Co., Ltd., Lanzhou 730050, PR China c Institute of Chemical Sciences, University of Peshawar, Peshawar 25120, Pakistan 1. Introduction Sesquiterpene lactones, which have been isolated from fungi, liverworts and members of angiosperm families, mainly the Asteraceae, represent one of the largest classes of plant secondary metabolites (Fischer, 1990, 1991). Vernonia anthelmintica Willd. (Asteraceae) is mainly distributed in tropical and sub-tropical regions of the world. The aerial parts of V. anthelmintica have been traditionally applied as a folk medicine in China for the treatment of asthma, hiccough, inflammatory swellings, sores and itching of the eyes, and used as a valuable anthelmintic medicine (Fatima et al., 2010). Vernonia species have been shown to produce various types of sesquiterpene lactones, such as germacranolides (Williams et al., 2005), eudesmanolides (Jakupovic et al., 1987), elemanolides (Ganjian et al., 1983) and guaianolides (Bardo ´n et al., 1988). From the previous literature (Liu et al., 2010), the major and bioactive constitutents in V. anthelmintica were also considered to be sesquiterpene lactones. However, in our previous work, eleven stigmastane-type (Liu et al., 2010; Bohlmann and Zdero, 1988) steroids and steroidal glycosides were isolated from the aerial parts of this species (Hua et al., 2012a,b). In our continuing endeavor to discover new bioactive sesquiterpene lactones from V. anthelmintica, two new guaianolides, named (1R,4R,5S,6R,7R,8S)-8,15-dihydroxyguaia-10(14),11(13)-dien- 12,6-olide (1) and (1R,4R,5S,6R,7R,8S,11S)-8,15-dihydroxyguaia- 10(14)-en-6,12-olide (2), together with two known elemanolides, ( 4S,5R,6R,7R,8S,10R,11S)-11,13-dihydrovernolepin ( 3) and (5S,6R,7R,8S,10S,11S)-melitensin (4) were isolated. In this paper, we report the isolation and structure elucidation of these sesquiterpenoids from V. anthelmintica. 2. Results and discussion Compound 1 was obtained as optically active colorless oil with a molecular formula of C 15 H 20 O 4 by HR-ESI-MS at m/z [M+NH 4 ] + 282.1697 (calc. for 282.1700). The IR spectra displayed intense absorptions for OH groups (3386 cm 1 ) and an ester carbonyl group (1750 cm 1 ). In the 1 H NMR spectrum of 1, two pairs of terminal methylene at d 4.97 (1H, brs), 5.05(1H, brs) and d 6.17 (1H, d, 3.2 Hz), d 6.26 (1H, d, 3.2 Hz), an oxygenated methylene at d 3.69 (m) and two oxygenated methines at d 3.91(t, 9.2 Hz), 3.86 (m) were observed (Table 1). The 13 C NMR spectrum of 1 showed a total of 15 carbons, which comprised an a-methylene-g-lactone at d 169.5 (C, C-12) and two double bonds carbons at d 138.2 (C, C-11), 123.4 (CH 2 , C-13), two olefinic carbons at 143.6 (C, C-10), 115.8 (CH 2 , C-14), three oxygenated carbons at d 80.6, 72.9, 66.1, three methylene carbons at d 29.0, 31.1, 44.3, and four methine carbons at d 46.9, 49.4, 48.8, and 52.3 (Table 1). Six degrees of unsaturation were attributed to one C 55 O group, two C 55 C bond, and three rings. Analysis of 1D-NMR spectra of compound 1 (Table 1 and Fig. 1) Phytochemistry Letters 7 (2014) 14–18 A R T I C L E I N F O Article history: Received 31 May 2013 Received in revised form 5 September 2013 Accepted 11 September 2013 Available online 8 October 2013 Keywords: Vernonia anthelmintica Guaianolides Elemanolides Cytotoxicity Biosynthetic relationships A B S T R A C T Two new guaianolides, (1R,4R,5S,6R,7R,8S)-8,15-dihydroxyguaia-10(14),11(13)-dien-12,6-olide (1) and (1R,4R,5S,6R,7R,8S,11S)-8,15-dihydroxyguaia-10(14)-en-6,12-olide (2), and two known elemanolides, (4S,5R,6R,7R,8S,10R,11S)-11,13-dihydrovernolepin (3) and (5R,6R,7R,8S,10R,11S)-melitensin (4) were isolated from the aerial parts of Vernonia anthelmintica Willd. The structures of these compounds were determined on the basis of IR, UV, MS, 1D-NMR and 2D-NMR, and their absolute configurations were deduced using the CD exciton chirality method and single-crystal X-ray diffraction. The possible biosynthetic relationships of compounds 1–4 are postulated. Compounds 1–4 were evaluated for their cytotoxicity against HL-60 and SMMC-7721 cell lines. ß 2013 Phytochemical Society of Europe. Published by Elsevier B.V. All rights reserved. * Corresponding author. Tel.: +86 0931 8912592; fax: +86 931 8912582. E-mail address: npchem@lzu.edu.cn (K. Gao). Contents lists available at ScienceDirect Phytochemistry Letters jo u rn al h om ep ag e: ww w.els evier.c o m/lo c ate/p hyt ol 1874-3900/$ – see front matter ß 2013 Phytochemical Society of Europe. Published by Elsevier B.V. All rights reserved. http://dx.doi.org/10.1016/j.phytol.2013.09.009