title: Isolation, structure, and biological activity of Phaeofungin, a cyclic lipodepsipeptide from a Phaeosphaeria sp. Using the Genome-Wide Candida albicans Fitness Test.
abstract: Phaeofungin (1), a new cyclic depsipeptide isolated from Phaeosphaeria sp., was discovered by application of reverse genetics technology, using the Candida albicans fitness test (CaFT). Phaeofungin is comprised of seven amino acids and a β,γ-dihydroxy-γ-methylhexadecanoic acid arranged in a 25-membered cyclic depsipeptide. Five of the amino acids were assigned with d-configurations. The structure was elucidated by 2D-NMR and HRMS-MS analysis of the natural product and its hydrolyzed linear peptide. The absolute configuration of the amino acids was determined by Marfey's method by complete and partial hydrolysis of 1. The CaFT profile of the phaeofungin-containing extract overlapped with that of phomafungin (3), another structurally different cyclic lipodepsipeptide isolated from a Phoma sp. using the same approach. Comparative biological characterization further demonstrated that these two fungal lipodepsipeptides are functionally distinct. While phomafungin was potentiated by cyclosporin A (an inhibitor of the calcineurin pathway), phaeofungin was synergized with aureobasidin A (2) (an inhibitor of the sphingolipid biosynthesis) and to some extent caspofungin (an inhibitor of glucan synthase). Furthermore, phaeofungin caused ATP release in wild-type C. albicans strains but phomafungin did not. It showed modest antifungal activity against C. albicans (MIC 16-32 μg/mL) and better activity against Aspergillus fumigatus (MIC 8-16 μg/mL) and Trichophyton mentagrophytes (MIC 4 μg/mL). The linear peptide was inactive, suggesting that the macrocyclic depsipeptide ring is essential for target engagement and antifungal activity.
authors.affiliation: Department of Medicinal Chemistry, Merck Research Laboratories , PO Box 2000, Rahway, New Jersey 07065, USA. sheo.singh@merck.com
authors.forename: Sheo B
authors.initials: SB
authors.lastname: Singh
authors.forename: John
authors.initials: J
authors.lastname: Ondeyka
authors.forename: Guy
authors.initials: G
authors.lastname: Harris
authors.forename: Kithsiri
authors.initials: K
authors.lastname: Herath
authors.forename: Deborah
authors.initials: D
authors.lastname: Zink
authors.forename: Francisca
authors.initials: F
authors.lastname: Vicente
authors.forename: Gerald
authors.initials: G
authors.lastname: Bills
authors.forename: Javier
authors.initials: J
authors.lastname: Collado
authors.forename: Gonzalo
authors.initials: G
authors.lastname: Platas
authors.forename: Antonio
authors.initials: A
authors.lastname: González del Val
authors.forename: Jesus
authors.initials: J
authors.lastname: Martin
authors.forename: Fernando
authors.initials: F
authors.lastname: Reyes
authors.forename: Hao
authors.initials: H
authors.lastname: Wang
authors.forename: Jennifer Nielsen
authors.initials: JN
authors.lastname: Kahn
authors.forename: Stefan
authors.initials: S
authors.lastname: Galuska
authors.forename: Robert
authors.initials: R
authors.lastname: Giacobbe
authors.forename: George
authors.initials: G
authors.lastname: Abruzzo
authors.forename: Terry
authors.initials: T
authors.lastname: Roemer
authors.forename: Deming
authors.initials: D
authors.lastname: Xu
mesh_terms: D000935:Antifungal Agents / Q000737:chemistry / Q000302:isolation & purification* / Q000494:pharmacology*; D001203:Ascomycota / Q000737:chemistry*; D002176:Candida albicans / Q000187:drug effects* / Q000235:genetics; D000077336:Caspofungin; D029627:Crassulaceae / Q000382:microbiology; D047630:Depsipeptides / Q000737:chemistry / Q000302:isolation & purification* / Q000494:pharmacology*; D054714:Echinocandins / Q000737:chemistry; D016678:Genome; D055666:Lipopeptides / Q000737:chemistry / Q000302:isolation & purification* / Q000494:pharmacology*; D008826:Microbial Sensitivity Tests; D015394:Molecular Structure; D019906:Nuclear Magnetic Resonance, Biomolecular; D018515:Plant Leaves / Q000382:microbiology; D018547:Plant Stems / Q000382:microbiology
chemical_list: D000935:Antifungal Agents; D047630:Depsipeptides; D054714:Echinocandins; D055666:Lipopeptides; C580912:phaeofungin; C539861:phomafungin; D000077336:Caspofungin