In our continuing research on the cytotoxic constituents of Taiwanese gorgonian corals, the EtOAc extracts of Briareum excavatum (Nutting) and Junceella fragilis (Ridley) were investigated, repectively. Twenty-four compounds, excavatolides D (1), F-K (2-7), M (8), U-Y (9-13);briaexcavatolides D (14), K (15), L (16), O(17), P (18); excavatolides B (19), C (20), E (21); briaexcavatolides B (22), C (23), and (1S*,2S*,5Z,7S*,8S*,9S*,10S*11R*,12R*,13Z,17R*)-2,12-diacetoxy-8,17-epoxy-9 hydroxy briara-5,13-dien-18-one (24) were isolated from B. excavatum. Three compounds, junceellolides E (25), F (26), and umbraculolide A (27) were isolated from J. fragilis. Among them, compounds 1-18, 25, and 26 are new products. All metabolites 1-27 are briarane-type compounds. The structures of metabolites 1-27 were determined by physical (mp, optical rotation) and spectral (UV, IR, MS, HRMS, 1D, and 2D NMR) data analyses and chemical methods and by comparison with the related physical and spectral data from other known briarane-type compounds. The structures, including the relative configurations of metabolites 1, 9, 15, 17, 18 and 25 were further confirmed by X-ray single-crystal analyses. Furthermore, the S-trans diene system in 1; the propionyloxy group at the C-4£] position of 13; the hydroxy groups at the C-8£]and C-17£\positions of 15 and 16; the independent functional groups at the C-2£],C-3£] and C-4£\ positions of 17 and 18, and the boat conformation in the six-membered ring of 25 and 26, all are the first observations in the briarane-type natural products. The cytotoxicity of the isolates against the P-388(mouse lymphocytic leukemia), KB (hum nasopharyngeal carcinoma), A549 (human lung adenocarcinoma), and HT-29 (human colon carcinoma) cancer cell lines were studied. In the cytotoxicity testing, 1, 6-8, 10, 16, 18, 20-22, and 24 show significant cytotoxicity against the grouth of P-388 cells; 7, 8, 20-22, and 24 show significant cytotoxicity toward KB cells; 7, 8, 20, and 21 show significant cytotoxicity toward A549 cells; 1, 7, 8, 18, 20, and 21 show significant cytotoxicity toward HT-29 cells.

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