Aplidium

Abstract: The distribution and abundance of littoral ascidians were analyzed with respect to thelr possible relationships with environmental stress. As part of a multidisciplinary research project on the benth~c communities in Algeciras Bay, southern Spain, a suite of environmental variables was measured (hydrodynamism, silting, suspended solids and organic matter). After displaying the similalities of fauna through clustering and ordination of sampling sites, the relationships between community differences and changes in the abiotic component were established based on the BIO-ENV procedure and Canonical Correspondence Analysis. Hydrodynamism and the percentage of organic matter in the silt is the variable combination that best explains (Spearman correlation of 0.82) the biotic structure. While all ascidians show a certain tolerance to diverse environmental factors, some species such as Ciona intestinalis. Diplosoma spongiforme, Phallusia mammillata, Microcosmus squamiger, Styela plicata and Synoicum argus could be considered as indicators of areas which have been subject to intense stress (substrate transformation, water stagnation and sedimentation excess) over long periods of time, whereas others such as Aplidium conicurn, Aplidium punctum. Clavelina dellavallei, Halocynthia papillosa and Stolonica socialis, which live only in natural and non-perturbed rock areas, could be categorized as species very sensitive to stress, as well as ind~cators of good conditions.

Abstract: Novel macrolides, lobatamides A-F (1-6), have been isolated from shallow water Australian collections of Aplidium lobatum, from a deep water collection of Aplidium sp., and from an unidentified Philippine ascidian. Full details of the isolation and structure elucidation of 1-6 are provided herein, along with results and analyses of the testing of lobatamides A-D (1-4) in the NCI human tumor 60 cell-line screen. The lobatamides share a common core structure with the recently described salicylihalamides, which were isolated from a Haliclona sp. sponge. COMPARE analyses of the mean-graph differential cytotoxicity profiles of the lobatamides and the salicylihalamides showed high correlations with each other but not with members of the NCI's standard agents database. These compounds, therefore, appear to comprise a new mechanistic class, meriting further antitumor investigations.

Abstract: The chemical study of the ascidian Aplidium haouarianum has led to the isolation of the new metabolites haouamines A (1) and B (2) which belong to a novel class of alkaloids. The structure of 1 was established by interpretation of its spectroscopic data and those of the N-methyl derivative 3, and confirmed by X-ray crystallographic analysis. The structure of 2 was deduced by spectroscopic study of its peracetyl derivative 2a. In solution each haouamine exists as an unseparable mixture of two interconverting isomers derived by the presence of a highly strained 3-aza-[7]-paracyclophane moiety in their structures. Compound 1 exhibits a selective cytotoxic activity against the HT-29 human colon carcinoma cell line.