Apoptolidins B and C: Isolation, Structure Determination, and Biological Activity.

Abstract

Apoptolidin (1) is a promising new therapeutic lead that exhibits remarkable selectivity against cancer cells relative to normal cells. We report the isolation, characterization, solution structure, stability, and biological activity of two new members of this family: apoptolidins B (2) and C (3). These new agents are found to have antiproliferative activity on par with or better than apoptolidin itself in an assay with H292 lung cancer cells.Apoptolidin (1) is a structurally novel macrocyclic lactone that exhibits remarkably selective activity against certain cancer cells. First isolated from the soil bacteria Nocardiopsis sp. in 1997 by Seto and co-workers, 1 apoptolidin was shown by NMR to possess a highly unsaturated 20-membered ring core with hydropyranyl appendages attached at positions C-9 and C-19. 2 Of special significance in current efforts to achieve greater selectivity in cancer chemotherapy, apoptolidin shows no cytotoxicity against normal cells even at high concentrations (>1 mM) but induces apoptosis in E1A-transformed rat glia cells at nanomolar concentrations. 1 In studies at the National Cancer Institute, apoptolidin was found to be in the top 0.1% of the most selective agents screened in the NCI-60 cell line assay. 3a By comparison to activity profiles of other compounds in this assay and through independent studies, apoptolidin was proposed to operate through inhibition of mitochondrial F 0 F 1 -ATPase. 3 wenderp@stanford.edu. Supporting Information Available Procedure for the H292 growth inhibition assay, HPLC methods for purification, and spectroscopic data for 2 and 3, including 1 H NMR, 13 C NMR, COSY, TOCSY, HMQC, HMBC, ROE distance restraints, IR, and HRMS is available free of charge via Internet at http://pubs.acs.org. The promising therapeutic potential of apoptolidin and its exceptional selectivity have stimulated efforts to identify the structural basis for its activity and its mode of action. While total synthesis studies are making important progress toward these goals, 4,5,6 the ready availability of apoptolidin from its source organism (109 mg/L of fermentation medium) offers facile access to apoptolidin as well as to various derivatives through semi-synthesis. NIH Public AccessImplementation of this "top down" strategy in our laboratory has thus far led to a higher yielding isolation procedure, to the identification of isoapoptolidin (4), 7 an isomer of apoptolidin that forms during isolation and assay, and to the synthesis and biological evaluation of numerous semi-synthetic analogs 8 which have uncovered new aspects of its mode of action. In the course of these studies we have also identified several new apoptolidins. We describe herein the isolation, structural characterization, stability, solution structure, and biological evaluation of two new members of this family: apoptolidin B (2) and apoptolidin C (3).During our efforts to obtain apoptolidin A (1) (the "A" appended to differentiate members of this now expanding family) through fermentation of Nocardiopsis sp.,...

Amycolatopsins A–C: antimycobacterial glycosylated polyketide macrolides from the Australian soil Amycolatopsis sp. MST-108494

“…11 Subsequent researchers extrapolated these assignments, and applied them to all other known examples of the apoptolidin structure class. 4,[8][9][10]12,14,15 To the best of our knowledge there are no published validations of these assignments that, in our view, remain tentative at best. In the case of the amycolatopsins, careful analysis of ROESY data revealed evidence of macrolactone conformational flexibility, cautioning against the use of such approaches to configurational assignment.…”

“…[5][6][7] The amycolatopsins share a common macrolide scaffold with the apoptolidins and ammocidins, and combine other unique structure features from both. For example, amycolatopsins share 4′-O-methylation with apoptolidins, 4,[8][9][10]14,15 and 25-methoxypropyl and 20-methyl moieties with ammocidins. [5][6][7] With respect to the latter, our suggested assignment of configurations about the C-20 to C-25 moiety in 1-3 provides a basis for making similar assignments in all known ammocidins (where these configurations are currently unassigned).…”

Nocardiopsisspecies: a potential source of bioactive compounds

“…With the discovery of minor Apoptolidin congeners (Apoptolidin B‐D), the Apoptolidin first isolated was renamed as Apoptolidin A (Wender et al . ). In addition to the anticancer activity against E1A‐ transformed glial cells, Apoptolidins inhibited growth of lung carcinoma H292 cells in the sub‐micromolar range, with Apoptolidin B being most active (Wender and Longcore ).…”