A new sesquiterpene benzoxazole, nakijinol B (3), its acetylated derivative, nakijinol B diacetate (6), and two new sesquiterpene quinones, smenospongines B (4) and C (5), were isolated from the methanol extract of the marine sponge Dactylospongia elegans. Also isolated were the known compounds dactyloquinone B and a 1:1 mixture of ilimaquinone and 5-epi-ilimaquinone. Their structures were determined on the basis of spectroscopic analyses and comparison with literature data. The isolated compounds were assessed for their cytotoxicity against a panel of human tumor cell lines (SF-268, H460, MCF-7, and HT-29) and a normal mammalian cell line (CHO-K1). All compounds were found to have activities in the range 1.8-46 μM and lacked selectivity for tumor versus normal cell lines.

From the dichloromethane/methanol extract of the crinoid Colobometra perspinosa, collected south east of Richards Island (Bedara), Family Islands, Central Great Barrier Reef, Australia, 3-(1′-hydroxypropyl)-1,6,8-trihydroxy-9,10-anthraquinone [one of the two stereoisomers of rhodoptilometrin, (1)], 3-propyl-1,6,8-trihydroxy-9,10-anthraquinone (3), 2-[(phenylacetyl)amino]ethanesulfonic acid (4), and 4-hydroxybutanoic acid (5) were isolated. Comparison of 1H- and 13C-NMR data for rhodoptilometrin (1) with those reported in the literature showed significant differences for some resonances associated with rings A and C. In an attempt to provide accurately assigned 1H- and 13C-NMR data, as well as to confirm the structure of 1, a thorough NMR investigation of this compound was undertaken. Measurements included: concentration dependent 13C, 1D selective NOE, HSQC, HMBC and 1,1-ADEQUATE. The NMR data for 4 and 5 are reported here for the first time, as is their occurrence from the marine environment. The in vitro anticancer activity of the original extract was found to be associated with 1, 3 and 5.

Bioassay-guided fractionation of extracts of the brown alga Sporochnus comosus led to the isolation of five new compounds, comosusols A-D (3-6) and comosone A (7). The structures of all isolated compounds were elucidated using standard one- and two-dimensional NMR techniques, as well as comparison with literature values. The cytotoxic activity of all compounds was investigated against a panel of human tumor and mammalian cell lines. These assays found eight of the nine compounds had GI(50) values in the 8-63 μM range.

While investigating the cytotoxic activity of the methanol extract of an Australian marine sponge Stelletta sp. (Demospongiae), a new diketopiperazine, cyclo-(4-S-hydroxy-R-proline-R-isoleucine) (1), was isolated together with the known bengamides; A (2), F (3), N (4), Y (5), and bengazoles; Z (6), C4 (7) and C6 (8). The isolation and structure elucidation of the diketopiperazine (1), together with the activity of 1–8 against a panel of human and mammalian cell lines are discussed.

Three new merosesquiterpenoids, metachromins U, V, and W (1-3), were isolated from a specimen of the marine sponge Thorecta reticulata collected off Hunter Island, Tasmania, Australia. Structures of the new compounds were elucidated through extensive NMR investigations and comparison with literature values. The cytotoxicities of 1-3 were assessed against a panel of human tumor cell lines (SF-268, H460, MCF-7, and HT-29) and a mammalian cell line (CHO-K1). All compounds were found to have 50% growth inhibition activities in the range 2.1-130 μM, with 2 being the most active (GI50 2.1-10 μM).