title: Merocyclophanes A and B, antiproliferative cyclophanes from the cultured terrestrial Cyanobacterium Nostoc sp.
abstract: The cell extract of a cultured terrestrial Nostoc sp. (UIC 10062), obtained from a sample collected at Grand Mere State Park in Michigan, displayed antiproliferative activity against the HT-29 human colon cancer cell line. Bioactivity-guided fractionation of the cell extract, combined with LC-MS analysis, led to the isolation of two cyclophanes, named merocyclophanes A and B (1 and 2). Their structures were determined by various spectroscopic techniques including HRESIMS, and 1D and 2D NMR analyses. The stereoconfiguration was assigned on the basis of X-ray crystallographic and CD analyses. The structures of merocyclophanes A and B (1 and 2) established a hitherto unknown [7.7]paracyclophane skeleton in nature, as characterized by α-branched methyls at C-1/14. Merocyclophanes A and B (1 and 2) displayed antiproliferative activity against the HT-29 human colon cancer cell line with IC₅₀ values of 3.3 and 1.7 μM, respectively.
authors.affiliation: Department of Medicinal Chemistry and Pharmacognosy, College of Pharmacy, University of Illinois at Chicago, Chicago, IL 60612, USA.
authors.forename: Hahk-Soo
authors.initials: HS
authors.lastname: Kang
authors.forename: Bernard D
authors.initials: BD
authors.lastname: Santarsiero
authors.forename: Hyunjung
authors.initials: H
authors.lastname: Kim
authors.forename: Aleksej
authors.initials: A
authors.lastname: Krunic
authors.forename: Qi
authors.initials: Q
authors.lastname: Shen
authors.forename: Steven M
authors.initials: SM
authors.lastname: Swanson
authors.forename: Heebyung
authors.initials: H
authors.lastname: Chai
authors.forename: A Douglas
authors.initials: AD
authors.lastname: Kinghorn
authors.forename: Jimmy
authors.initials: J
authors.lastname: Orjala
mesh_terms: D000970:Antineoplastic Agents / Q000737:chemistry* / Q000302:isolation & purification / Q000494:pharmacology*; D049109:Cell Proliferation / Q000187:drug effects; D046508:Culture Techniques; D000458:Cyanobacteria / Q000737:chemistry* / Q000145:classification / Q000235:genetics / Q000254:growth & development; D003516:Cycloparaffins / Q000737:chemistry* / Q000302:isolation & purification / Q000494:pharmacology*; D019073:HT29 Cells; D006801:Humans; D020128:Inhibitory Concentration 50; D010802:Phylogeny; D012329:RNA, Bacterial / Q000235:genetics; D012336:RNA, Ribosomal, 16S / Q000235:genetics; D013237:Stereoisomerism
chemical_list: D000970:Antineoplastic Agents; D003516:Cycloparaffins; D012329:RNA, Bacterial; D012336:RNA, Ribosomal, 16S