Antitumor Agents. Part 218: Cappamensin A, a New In Vitro Anticancer Principle, from Capparis sikkimensis y Jiu-Hong Wu, a Fang-Rong Chang, a Ken-ichiro Hayashi, a Hiroaki Shiraki, a Chih-Chuang Liaw, a Yuka Nakanishi, a Kenneth F. Bastow, a Donglei Yu, a Ih-Sheng Chen b and Kuo-Hsiung Lee a, * a Natural Products Laboratory, School of Pharmacy, University of North Carolina, Chapel Hill, NC 27599, USA b School of Pharmacy, Kaohsiung Medical University, Kaohsiung, Taiwan Received 5 September 2002; accepted 19 March 2003 Abstract—A new inhibitor of in vitro tumor cell replication, cappamensin A (1) (2H-1,4-benzoxazin-3(4H)-one, 6-methoxy-2-methyl- 4-carbaldehyde), was isolated from the roots of Capparis sikkimensis subsp. formosana using bioactivity-guided fractionation. The structure of 1 was established by spectroscopic methods, including 2D NMR analyses. Compound 1 displayed significant in vitro anticancer activity against ovarian (1A9), lung (A549), ileocecal (HCT-8), breast (MCF-7), nasopharyngeal (KB), and vincristine resistant (KB-VIN) human tumor cell lines with ED 50 values  4 mg/mL (mean GI 50 value of 15.1 mM). # 2003 Elsevier Science Ltd. All rights reserved. Capparis sikkimensis subsp. Formosana (Capparaceae) is a native Taiwanese shrub with overhanging, climbing branches. The roots and seeds of the genus Capparis have been used as antirheumatic, tonic, expectorant, antispasmodic, and analgesic agents in Chinese folk medicine. 2 Their healing properties have also been known since antiquity among numerous tribes in differ- ent Mediterranean countries. 3,4 In a screening program dedicated to isolating antitumor compounds from plant sources, the chloroform extract of Capparis sikkimensis 5 showed significant in vitro cytotoxicity against various human tumor cell lines. Bioactivity-directed fractionation 6 of the active extract against A594 lung cancer and 1A9 ovarian cancer cells in tissue culture led to the isolation of compound 1 as the major novel active principle. The structure of 1, which is provisionally named cappamensin A, was determined by chemical modification and 2D NMR spectra, including 1 H- 1 H COSY, HMQC, HSQC, and HMBC techniques. 7 We report herein the isolation and structural characterization of cappamensin A. Cappamensin A (1) has the molecular formula C 11 H 11 O 4 N as determined by ESI-MS (positive: m/z 244, [M+Na] + , negative: m/z 220, [MH] + ) and ele- mental analysis. Its 1 H NMR spectrum indicated allyl methyl (d 2.51, s, 3H), methoxy (d 3.71, s, 3H), 5, 6, 8 trisubstituted benzene (d 8.58, d, J=8.7 Hz, 1H; d 7.12, dd, J=8.7 Hz, J=2.4 Hz, 1H; d 7.04, d, J=2.4 Hz, 1H), amide aldehyde (d 10.60, s, 1H), and chelated hydroxy (d 13.32, s, 1H) protons. The 13 C NMR spectrum showed 11 signals including an amido aldehyde, two olefinic, and six benzene ring signals. The presence of an amido aldehyde and a hydroxy group was also sup- ported by IR absorptions at 1733 and 3450 cm 1 , respectively. The position of the methoxy group at C-7 in the benzene ring was confirmed by HMBC corre- lation of d H 7.12 (H-6, dd, 8.7, 2.4 Hz) with d C 120.8 (C-4a). Cross peaks in the HMBC spectrum between the amido aldehyde proton and C-4a indicated that the nitrogen was attached to C-4a. The chemical shifts of the OH proton at d 13.32 and of C-3 at d 143.98 sug- gested that the hydroxy group was located at C-3 and interacted with the aldehyde by hydrogen bonding. 1 H– 13 C long-range coupling between the hydroxy group and C-3 supported this conclusion. The position of the methyl group at C-2 was determined by a HMBC cross peak between the methyl protons and C-3 and by the NMR chemical shifts (d H 2.51 ppm and d C 18.5 ppm). 0960-894X/03/$ - see front matter # 2003 Elsevier Science Ltd. All rights reserved. doi:10.1016/S0960-894X(03)00379-2 Bioorganic & Medicinal Chemistry Letters 13 (2003) 2223–2225 y For Part 217 of this series, see ref 1. *Corresponding author. Tel.: +1-919-962-0066; fax: +1-919-966-3893; e-mail: khlee@unc.edu