An Anthraquinone with Potent Quinone Reductase-Inducing Activity and Other Constituents of the Fruits of Morinda citrifolia (Noni) Alison D. Pawlus, †,‡ Bao-Ning Su, § William J. Keller, ⊥ and A. Douglas Kinghorn* ,†,§ Program for Collaborative Research in the Pharmaceutical Sciences, Department of Medicinal Chemistry and Pharmacognosy, College of Pharmacy, University of Illinois at Chicago, Chicago, Illinois 60612, Division of Medicinal Chemistry and Pharmacognosy, College of Pharmacy, The Ohio State University, Columbus, Ohio 43210, and Nature’s Sunshine Products, Inc., 1655 N. Main Street, Spanish Fork, Utah 84660 Received September 30, 2005 Abstract: Morinda citrifolia, commonly known as noni, has a long history of utilization throughout much of tropical Polynesia and is considered to be the second most important medicinal plant in the Hawaiian Islands. Recently, the use of noni as a dietary supplement in the United States has greatly increased. Bioassay-guided fractionation of a dichloromethane- soluble partition of a MeOH extract of noni fruits has led to the isolation of an extremely potent quinone reductase inducer, 2-methoxy-1,3,6-trihydroxyanthraquinone (1). This new an- thraquinone (1) was nearly 40 times more potent than a positive control, L-sulforaphane. Furthermore, compound 1 demonstrated no discernible cytotoxicity at the highest dose tested. In addition to compound 1, 11 known compounds were also isolated and identified in the present investigation. This is the first report of the isolation of anthraquinones from noni fruits. Currently, the use of Morinda citrifolia L. (Rubiaceae), commonly called noni, as a botanical dietary supplement is growing in the United States and elsewhere. The purported uses include for arthritis, cardiovascular disease, cancer, and as a tonic for promoting overall health. Noni is a tree or large bush distributed in tropical areas from India to Hawaii, where it is widely considered a valuable medicinal plant. Although all parts of M. citrifolia are used ethnobotanically for various medical ailments, the ripe fruits are currently the predominant part used in the United States. 1 To date, the majority of studies done on noni have demonstrated a number of potential biological activities, yet the phytochemical constituents responsible for the ascribed activities are largely unknown. 2 In our continuing investigation of botanical dietary supplements for cancer chemopreventive activities, 3 we tested a noni fruit extract for activity in a quinone reductase (QR) induction bioas- say. 4,5 QR is a phase II metabolizing enzyme and is induced in conjunction with other protective phase II enzymes by a chemically diverse array of compounds. The induction of phase II enzymes is considered cancer chemopreventive in that potential oxidative and electrophilic molecules can be more readily metabolized and excreted before they can interact with cellular macromolecules such as DNA. QR is also responsible for maintaining the reduced states of antioxidants such as R-tocopherol and coenzyme Q 10 . 6 Hence, QR inducers are sometimes referred to as “indirect antioxidants”, and this activity is considered protective at the initiation stage of carcinogenesis. 7 Herein we describe the isolation, identification, and biological activity of 12 compounds from M. citrifolia fruits, including the structure elucidation of one new anthraquinone (1) with potent QR induction activity. The CH 2 Cl 2 -soluble partition of the MeOH extract of noni fruits exhibited a potent concentration to double QR (CD) activity value of <2.5 µg/mL. Bioassay-guided fractionation of this extract led to the isolation of one new anthraquino- ne, 2-methoxy-1,3,6-trihydroxyanthraquinone (1), as well as 11 known compounds, 1,8-dihydroxy-2-hydroxymethyl- 5-methoxyanthraquinone(2), 8 1,3-dihydroxy-2-methoxyanthra- quinone (3), 9 1,6-dihydroxy-5-methoxy-2-methylanthraquino- ne (4), 10 2-hydroxy-1-methoxyanthraquinone (5), 11,12 bal- anophonin, 13 4-hydroxy-3-methoxycinnamaldehyde, 14 -hy- droxypropiovanillone, 15 1-monopalmitin, 16 scopoletin, -sito- sterol, and vanillin. The structures of these known com- pounds were identified by comparing their physical and spectroscopic data ([R] D , 1 H NMR, 13 C NMR, DEPT, 2D NMR, and MS) with those of published values or by comparing with an authentic sample (-sitosterol, scopole- tin, and vanillin) directly. Compound 1 was obtained as a red amorphous powder, and the solubility of this isolate was very limited in common organic solvents such as acetone, CHCl 3 , and MeOH. A molecular formula of C 15 H 10 O 6 was determined for compound 1 on the basis of the observed sodiated molecular ion peak at m/z 309.0370 (calcd for C 15 H 10 O 6 - Na, 309.0375) in its HRESIMS. The NMR spectra (both 1D and 2D) of 1 were acquired using a mixture of CDCl 3 and CD 3 OD (ca. 5:1) as the solvents. The 1 H NMR spectrum of compound 1 displayed signals for a 1,2,4-trisubstituted aromatic ring at δ H 8.15 (1H, d, J ) 8.4 Hz, H-8), 7.55 (1H, br s, H-5), and 7.17 (1H, br d, H-7), an aromatic singlet at δ H 7.32 (1H, s, H-4), and a three-proton singlet at δ H 4.02 (3H, s, OMe-2) typical for an aromatic methoxy group. In addition to a characteristic methoxy group signal at δ C 60.9, the 13 C NMR spectrum of 1 displayed 14 carbon signals. The chemical shifts of these 14 resonance signals suggested the presence of two aromatic rings and two doubly conju- gated carbonyl carbons (δ C 187.1, 183.2) in the molecule of 1. These NMR data suggested that compound 1 is an * To whom correspondence should be addressed. Tel: +1-614-247-8094. Fax: +1-614-247-8081. E-mail: kinghorn.4@osu.edu. † Program for Collaborative Research in the Pharmaceutical Sciences. ‡ Present address: The Ohio State University. § The Ohio State University. ⊥ Nature’s Sunshine Products, Inc. 10.1021/np050383k CCC: $30.25 © xxxx American Chemical Society and American Society of Pharmacognosy PAGE EST: 2.1 Published on Web 00/00/0000