There are more than 100 species of the genus Artabotrys throughout tropical Africa and East Asia.1) Artabotrys uncinatus (LAM.) MERR. (Annonaceae) is widely distributed throughout southern Taiwan, and the roots and fruits are used for the treatment of malaria and scrofula.2) Previous literature has shown this genus to contain alkaloids, triterpenoids, lignans, flavonoids, and steroids.2-6) Among them, yingzhaosu analogues showed notable antimalarial activities in vitro; alkaloids showed cytotoxic and antithrombotic activitives. 5) In this study, we investigated the stem parts of A. uncinatus, and two new compounds, 4,5-dioxoartacinatine (1) and 24-methylene lanosta-7,9(11)-diene-3-one (2), along with thirty known compounds: cloven-2b,9a-diol (3), 7) caryolane-1,9b-diol (4), 7) 1-methoxy-9-caryolanol (5), 8) spathulenol (6) (Fig. 3).5) The 13 C-NMR spectrum exhibited the presence of three methyl, two methylene, three methine, and eleven quaternary carbons. In comparison with the literature data, 25) the di-ketone groups in 4,5-dioxoaporphines usually resonate at d C 178 and 157 ppm, respectively. Compound 1 showed the signals at d C 175.0 and 152.4 ppm, which are coincident with the assignments of 4,5-di-ketone groups. H-3 appeared at d H 8.25 indicating the existence of a carbonyl group at the peri-position. The HMBC spectra gave further support for the structure determination of 1, the correlations between 1-OCH 3 and C-1, and 2-OCH 3 and C-2 confirmed the methoxy groups at C-1 and C-2. The correlations between H-3 and C-2/C-11c/C-4, and between N-CH 3 and C-5/C-6a indicated the ketone groups at C-4 and C-5. The significant NOESY correlation between H-7 and H-8 together with the aforementioned assignments also proved the carbonyl group was located at C-11. The above evidence and comparison with the spectral data reported for artacinatine (18), cepharadione-A, and aristolodione indicated the structure of 1 was 4,5-dioxoartacinatine. 25) In our previous study, artacinatine (18) isolated from this plant with the same Dring moiety had been evidenced by X-ray crystalline analysis. Compound 18 possesses a 10a-hydroxyl function. Com- Two new compounds, 4,5-dioxoartacinatine (1) and 24-methylenelanosta-7,9(11)-diene-3-one (2), together with thirty known compounds were isolated and characterized from the stems of Artabotrys uncinatus. Structures of the new compounds were determined by spectral analysis. New Constituents from Stems of Artabotrys uncinatus