Contents lists available at ScienceDirect Phytochemistry Letters journal homepage: www.elsevier.com/locate/phytol Three new chemical constituents of Korthalsella japonica Yu-Hsuan Lan a, ⁎ , Hsiu-Hui Chan b , Chuan-Nien Chuang b , Tran-Dinh Thang c , Yann-Lii Leu b,d, ⁎⁎ a School of Pharmacy, China Medical University, Taichung 40402, Taiwan b Graduate Institute of Natural Products, College of Medicine, Chang Gung University, Taoyuan 33302, Taiwan c Faculty of Chemistry, Vinh University, 182-Le Duan, Vinh City, Nghean Province, Viet Nam d Center for Traditional Chinese Medicine, Chang Gung Memorial Hospital, Taoyuan, Taiwan ARTICLE INFO Keyword: Korthalsella japonica Korthalin 6′,4″-dihydroxy-2′,3″-dimethoxychalcone-4′-O- β-D- glucopyranoside ABSTRACT The mistletoe Korthalsella japonica is used in traditional Chinese medicine to treat injury and to enhance blood circulation. Phytochemical constituents of this plant are not as well known as those of other species. In this study, three new compounds, korthalin (1), 6′,4″-dihydroxy-2′,3″-dimethoxy chalcone-4′-O-β-D-glucopyranoside (2) and viscolin 4′,4″-di-O-β-D-glucopyranoside (3), together with twenty-eight compounds (4-31) were isolated from Korthalsella japonica. The structures of all compounds were established on the basis of spectroscopic data analysis. 1. Introduction Korthalsella japonica, which is distributed in tropical Asia, Australia to Polynesia, belongs to family of Loranthaceae. It is small parasitic subshrub that grows on the following species: Ligustrum japonicum Thunb., Litsea mushaensis (Hayata) Hayata, Neolitsea acuminatissima (Hayata) Kanehira & Sasaki, Cinnamomum sp., Symplocos stellaris Brand., Symplocos morrisonicola Hayata, Osmantus matsumuranus Hayata, Pouteria obovate (R. Brown) Baehni, Syzygium buxifolium Hook. & Am., and Rhododendron kawakawii Hayata (Chiu, 1996). The che- mical constituents of this mistletoe have not yet been widely studied. Until now, only several constituents, such as chrysoeriol-4′-O-glucoside, luteolin 6,8-di-C-β-D-glucopyranoside, apigenin 6,8-di-C-β-D-glucopyr- anoside, chrysoeriol 6,8-di-C-β-D-glucopyranoside, phytosterol, olea- nolic acid and fatty acids, have been reported (Fukunaga et al., 1989; Kim et al., 2016). As part of our continuing investigation on the che- mical constituents from natural plants, we herein describe the detailed structures of three new compounds korthalin (1), 6′,4″-dihydroxy-2′,3″- dimethoxychalcone-4′-O-β-D-glucopyranoside (2) and viscolin 4′,4″-di- O-β-D-glucopyranoside (3), along with twenty-eight known compounds. 2. Results and discussion Compound 1 was obtained as a yellowish oil. The HREI-MS of 1 exhibited a molecular ion peak at m/z 290.1155 (calcd 290.1154), consistent with the molecular formula C 16 H 18 O 5 , which was supported by the presence of 16 carbon signals in its 13 C NMR spectrum. The UV spectrum of 1 showed absorption maxima at 278 and 227 nm. The IR spectrum showed strong absorption peaks for hydroxy (3421 cm -1 ) and carbonyl groups (1730 cm -1 ). The 1 H NMR spectrum showed three aromatic protons at δ 6.83 (1H, d, J = 8.0 Hz, H-13), 6.70 (1H, dd, J = 8.0, 1.2 Hz, H-14) and 6.67 (1H, d, J = 1.2 Hz, H-10), indicating a typical ABX moiety. In addition, two methoxy groups at δ 4.27 (3H, s,) and 3.90 (3H, s), four methylenes at δ 2.88 (2H, s, H-2), 2.60 (2H, t, J = 7.6 Hz, H-8), 2.44 (2H, t, J = 7.6 Hz, H-6) and 1.84 (2H, quint., J = 7.6 Hz, H-7) were observed in the 1 H NMR spectrum. The 1 H– 1 H COSY spectrum showed the correlations between H-7 (δ 1.84) and H-6 (δ 2.44)/H-8 (δ 2.60) and revealed the CH 2 CH 2 CH 2 sequence in this molecule (Fig. 2). The 13 C NMR spectrum combined with the HMQC experiments indicated the presence of four methylenes (δ 42.6, 35.9, 29.5, 22.1), two methoxy groups (δ 60.0, 56.3), two conjugated ketones (δ 196.7, 195.9), two quaternary olefinic carbons (δ 166.5, 141.3) and six aromatic carbons (δ 146.7, 144.2, 133.9, 121.4, 114.6, 111.4). The HMBC spectrum showed 2 J and 3 J correlations between δ 2.88 (H-2) and δ 196.7 (C-1), δ 195.9 (C-3), δ 166.5 (C-4) and δ 141.3 (C-5), suggesting the 4-cyclopentene-1,3-dione moiety. The position of the trisubstituted aromatic ring at C-5 was elucidated using the HMBC correlations of δ 2.60 (H-8) to δ 133.9 (C-9), δ 121.4 (C-10) and δ 111.1 (C-14) and of δ 1.84 (H-7) to δ 133.9 (C-9) and δ 35.9 (C-8). Further- more, the 4-cyclopentene-1,3-dione moiety was located at C-6 using the HMBC correlations of δ 2.44 (H-6) to δ 196.7 (C-1), δ 141.3 (C-5) and δ 166.5 (C-4) and of δ 1.84 (H-7) to δ 141.3 (C-5), δ 133.9 (C-9), δ 35.9 (C-8) and δ 22.1 (C-6). In addition, two methoxy groups at δ 4.27 and 3.90 showed 3 J HMBC correlations with δ 166.5 (C-4) and δ 146.7 (C- https://doi.org/10.1016/j.phytol.2017.12.003 Received 12 September 2017; Received in revised form 4 December 2017; Accepted 5 December 2017 ⁎ Corresponding author. ⁎⁎ Corresponding author at: Graduate Institute of Natural Products, College of Medicine, Chang Gung University, Taoyuan 33302, Taiwan. E-mail addresses: lanyh@mail.cmu.edu.tw (Y.-H. Lan), ylleu@mail.cgu.edu.tw (Y.-L. Leu). Phytochemistry Letters 23 (2018) 132–136 1874-3900/ © 2017 Phytochemical Society of Europe. Published by Elsevier Ltd. All rights reserved. T