Acetylcholinesterase-inhibiting activity of marinoquinoline A (1), a new pyrroloquinoline from a novel species of a marine gliding bacterium Rapidithrix thailandica, was assessed (IC 50 4.9 μM). Two related pyrrole derivatives, 3-(2'-aminophenyl)-pyrrole (3) and 2,2-dimethyl-pyrrolo-1,2-dihydroquinoline (4), were also isolated from two other strains of R. thailandica. The isolation of 3 from a natural source is reported here for the first time. Compound 4 was proposed to be an isolation artifact derived from 3.The two isolated compounds were virtually inactive in the acetylcholinesterase-inhibitory assay (enzyme inhibition < 30% at 0.1 g L -1 ).

Renieramycins M (1m) and N (1n) were isolated from the Thai sponge Xestospongia sp., pretreated with potassium cyanide in methanolic buffer solution, and their structures and relative stereochemistries were elucidated on the basis of spectroscopic data. This strategy is the first example of the gram-scale preparation of this series of compounds and presents a potential solution for increasing the gram-scale supply of novel natural products from marine sources.

Two new norsesterterpene 1,2-dioxanes, mycaperoxides A (2) and B (3), have been isolated from a Thai sponge of the genus Mycale. Their relative structures were determined by X-ray and spectroscopic methods and their absolute configurations assigned by applying the Kusumi and Kakisawa modification of Mosher's method. Both compounds showed significant cytotoxicity and in vitro antiviral activity.

Bioassay-guided fractionation of the EtOAc extract of a marine Bacillus sp. Sc026 culture broth has led to the isolation of the known compound, macrolactin F (1), together with two new compounds, 7-O-succinyl macrolactin F (2) and 7-O-succinyl macrolactin A (3). The chemical structures of 1-3 were elucidated on the basis of spectral data analyses and literature data comparison. Compounds 1-3 exhibited antibacterial activity against Bacillus subtilis and Staphylococcus aureus.

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Four minor renieramycin-type derivatives, including renieramycins O (1o) and Q-S (1q-s), were isolated from the sponge Xestospongia sp. pretreated with potassium cyanide. Their structures were elucidated by comparison of spectral data with those of recently reported renieramycins M (1m) and N (1n). The results of transformation and cytotoxicity measurements are also described.

Guided by brine shrimp toxicity and human tumor cell toxicity, fractionation of the alcoholic extract from the stem bark of Goniothalamus marcanii led to the isolation of four new 1-azaanthraquinones: marcanines B (3), C (4), D (5), and E (6), along with two known derivatives: marcanine A and dielsiquinone. A new 5-hydroxy-3-amino-2-aceto-1,4-naphthoquinone (7), a possible 1-azaanthraquinone biosynthetic precursor, was also isolated. The structures of the compounds were elucidated by spectroscopic analyses, mainly 1D and 2D NMR techniques ((1)H, (13)C, NOEDS, COSY, HMQC, and HMBC), as well as comparison with literature data. All the compounds except 6 were evaluated for cytotoxic activity. They exhibited significant cytotoxicity against several human tumor cell lines, A-549, HT-29, MCF7, RPMI, and U251 with the ED(50) in the range of 0.04-3.03 microM.