Malettinin E, an antibacterial and antifungal tropolone produced by a marine Cladosporium strain

Abstract

The isolation and structure elucidation of malettinins A-C (1-3) along with the new malettinin E (4) are described. The compounds were produced by the fungus Cladosporium sp. strain KF501, which was isolated from the German Wadden Sea. The malettinins are built up of tropolone/dihydropyran ring structures linked to a furan ring. The structure elucidation of the isolated compounds was achieved by means of one-and two-dimensional NMR spectroscopy supported by mass and UV data. The relative configuration of 4 was determined on the basis of single-crystal X-ray diffraction analysis. 1-4 exhibited antibacterial and antifungal activities when profiled against Xanthomonas campestris and Trichophyton rubrum. The influence of the chemical structure of the furan ring and of configurational changes on biological activities was observed.

Natural Products from Marine Fungi—Still an Underrepresented Resource

“…KF525 [ 31 , 32 ], B. robillardoides LF550 [ 27 ], Cladosporium sp. KF501 [ 33 ], and Massariosphaeria typhicola KF970 [ 34 ]. A number of new compounds and their bioactivities from these studies were reported.…”

“…colombiae . Hence, strain KF501 could be clearly identified as a member of the genus Cladosporium , but identification to the species level could not be achieved [ 33 ].…”

“…Originally, malettinins A–C and malettinin D were reported from an unidentified fungus [ 84 , 85 ] and for the first time Cladosporium sp. strain KF501 was shown to produce malettinins A–C ( 41 – 43 ) and the new malettinin E ( 44 ), which is the 13-epimer of malettinin C ( 43 ) ( Figure 8 ) [ 33 ]. Malettinin D was not found [ 33 ].…”

“…strain KF501 was shown to produce malettinins A–C ( 41 – 43 ) and the new malettinin E ( 44 ), which is the 13-epimer of malettinin C ( 43 ) ( Figure 8 ) [ 33 ]. Malettinin D was not found [ 33 ].…”

The antimicrobial potential of algicolous marine fungi for counteracting multidrug-resistant bacteria: phylogenetic diversity and chemical profiling

“…Among marine microorganisms, fungi play a crucial role, being a reservoir of biologically active secondary metabolites [4][5][6]. Recently, several new metabolites from marine fungi have been reported to display notable antibacterial activities [7][8][9]. Despite their proven biosynthetic potential, scientific research has not intensively focused on marine fungi for seeking new drugs [10].…”