Contents lists available at ScienceDirect Phytochemistry journal homepage: www.elsevier.com/locate/phytochem Cytotoxic sesquiterpene glucosides from Fissistigma pallens Ngo Sy Thinh c,d , Nguyen Thi Bich Thu c,e , Tran Minh Ngoc c , Nguyen Minh Khoi c , Bui Huu Tai a , Phan Van Kiem a , Chau Van Minh a , Nguyen Xuan Nhiem a,** , Yohan Seo b , Wan Namkung b , SeonJu Park b , Seung Hyun Kim b,* a Institute of Marine Biochemistry (IMBC), Vietnam Academy of Science and Technology (VAST), 18 Hoang Quoc Viet, Cau Giay, Hanoi, Viet Nam b Yonsei Institute of Pharmaceutical Sciences, College of Pharmacy, Yonsei University, Incheon, 406-840, South Korea c National Institute of Medicinal Materials, 3B Quang Trung, Hoan Kiem, Hanoi, Viet Nam d 354 Military Hospital, 120 Doc Ngu, Ba Dinh, Hanoi, Viet Nam e College of Pharmacy, Duy Tan University, 254 Nguyen Van Linh, Thanh Khe, Da Nang, Viet Nam ARTICLE INFO Keywords: Fissistigma pallens Annonaceae Sesquiterpene Fissispallin Cytotoxic activity ABSTRACT Six undescribed sesquiterpene glucosides, fissispallins A-F, and one known sesquiterpene glucoside, fissispallin, were discovered in the leaves of Fissistigma pallens (Finet & Gagnep.) Merr. The structures were determined using spectroscopic methods, including 1D, 2D NMR, and MS. All compounds were evaluated for cytotoxic activity against three human cancer cell lines, HT-29, A-2058, and A-549. Fissispallin A showed potent activity with the IC 50 values less than 1.5 μM against all tested human cancer cell lines. Fissispallin also showed potent activity with IC 50 value of 0.4 ± 0.3 on the A-2058 cancer cell lines. Fissispallins B-D showed significant cytotoxic activity against all the tested cancer cell lines with IC 50 values ranging from 3.8 to 7.2 μM. 1. Introduction Fissistigma is a genus of the plant family Annonaceae that includes 66 species of which 23 species of Fissistigma are distributed in Vietnam (Ban, 2000). Some species have been found to contain alkaloids (Chia et al., 1998; Wu et al., 1990) and sesquiterpenes (Porzel et al., 2000). In addition, the compounds and extracts from the Fissistigma species have been found to exhibit cytotoxic (Fan et al., 2012) and anti-in- flammatory effects (Ge et al., 2013). The essential oil extracted from some species of this genus is also used as a fragrance. Essential oils of this species are primarily comprised of sesquiterpenes (Thang et al., 2014). Fissistigma pallens (Finet & Gagnep.) Merr. (Annonaceae) is an im- portant climbing shrub that grows in the Northern regions of Vietnam. Other plants in the Fissistigma genus, including F. pallens provide an essential oil fragrance. F. pallens has been used in traditional medicine to treat diseases like muscular atrophy, hepatomegaly, hepatospleno- megaly, traumatic injuries, sciatic muscle strains, arthritis, rheumatism, and asthma. Recent phytochemical research has shown that F. pallens contains alkaloids (Höferl et al., 2013) that contribute to anti-in- flammatory and anti-cancer activities. Therefore, it is necessary to un- derstand the constituents and function of organic compounds contained in the plant. Here, we report the structure of six undescribed sesqui- terpene glucosides and one known compound. We also report and their cytotoxic activities. 2. Results and discussion The leaves of F. pallens were sonicated with hot methanol to yield methanol (MeOH) extract. The MeOH extract was suspended in H 2 O and successively partitioned with n-hexane, chloroform, and ethyl acetate (EtOAc) to yield the layers. Six undescribed sesquiterpene glu- cosides and one known compound were isolated using various chro- matographic resin and isolation techniques. Compound 1 was obtained as a white amorphous powder and its molecular formula was determined to be C 30 H 42 O 7 from HRESIMS at m/z 537.2822 [M+Na] + (Calcd. for [C 30 H 42 O 7 Na] + , 537.2823). The 1 H NMR spectrum of 1 (in CDCl 3 ) showed the proton signals of a vinyl group at δ H 4.78 (d, J = 17.2 Hz), 4.80 (d, J= 11.2 Hz), and 5.72 (dd, J = 11.2, 17.2 Hz), two methylene olefin protons at δ H 4.47 (s) and 4.69 (s), four methyl groups at δ H 0.87, 1.12, 1.17, and 1.59 (each 3H, s); two olefinic protons; five aromatic protons; and one anomeric proton. The 13 C NMR and DEPT spectra of 1 displayed the signals of 30 carbons, including one carbonyl, four non-protonated carbons, fifteen https://doi.org/10.1016/j.phytochem.2019.112255 Received 4 May 2019; Received in revised form 29 December 2019; Accepted 30 December 2019 * Corresponding author. College of Pharmacy, Yonsei Institute of Pharmaceutical Sciences, Yonsei University, Incheon, 21983, South Korea. ** Corresponding author. Institute of Marine Biochemistry, Vietnam Academy of Science and Technology (VAST), 18 Hoang Quoc Viet, Cau Giay, Hanoi, Viet Nam. E-mail addresses: nxnhiem@yahoo.com (N.X. Nhiem), kimsh11@yonsei.ac.kr (S.H. Kim). Phytochemistry 172 (2020) 112255 0031-9422/ © 2020 Elsevier Ltd. All rights reserved. T