A novel nitrogenous macrolide, designated salarin C (I), was isolated from the Madagascan sponge Fascaplysinopsis sp. The structure of the compd. was elucidated by interpretation of MS and 1D and 2D NMR spectra. Salarin C is closely related to salarin A and is considered to be the precursor of salarins A and B. Air oxidn. was found to transform I to salarin A. Salarin C was found to inhibit cell proliferation of human leukeamic cell lines UT-7 and K562 and the murine pro-B cell line Ba/F3 at concns. of 0.0005-0.5 mg/mL. A possible biogenesis is discussed. [on SciFinder(R)] Erratum Ibid 2008;49(37):5437: Concns. of the active compds. were erroneously given in millimolars (mM) rather than in micromolars (μM) and in mg/mL rather than in μg/mL. The cor. penultimate sentence of the Abstr., page 4356, and the passage on page 4357 beginning six lines from the bottom of the left column to the end of that paragraph are given. [on SciFinder(R)]