Planta Med 2013; 79 - SL42
DOI: 10.1055/s-0033-1351868

Identification of quinolactin alkaloids from fungi associated to Brazilian red algae Dichotomaria marginata by LC-PDA-MS and LC-MSn

TJ Andrade 1, AH Somensi 1, MN Lopes 1, AR Araujo 1, M Jaspars 2, DH Silva 1
  • 1Institute of Chemistry, UNESP
  • 2University of Aberdeen

Fungi isolated from marine organisms have been shown to produce several interesting secondary metabolites with important biological activities. Such chemical diversity may be associated to environmental stress conditions and may represent an important source of NCE for bioprospection. Quinolactins belong to a rare fungi-alkaloid class with a unique N-methyl-quinolone moiety fused to a lactam ring and present several bioactivities1. Fungi strain Dm1 was isolated from red alga Dichotomaria marginata, collected from Brazil SE coast, and was grown in sterile rice solid media at 26oC 2, which was then extracted with MeOH. The MeCN fr. from the MeOH extract was chromatographed over Sephadex LH-20 and fr. 4 afforded quinolactin (QL) alkaloids B1, B2 and A, whereas fr. 5 afforded quinolactin D1 after purification by HPLC-DAD. Structural determination of pure compounds was based on HRMS, UV, and NMR spectral analyses, in addition to comparison with literature data and Antimarin® databank. UV data indicated the presence of similar chromophores with λmax at ca. 247 and 320nm. HRMS and tandem MS analyses using both negative and positive ion modes for the isolated compounds indicated their molecular formula and structural features, as for QL B1: C15H16O2N2 [M+H 257], which showed one fragment at m/z 214 [-CHNO]; QL B2: C15H16O3N2 [M+H 273], with product ions at m/z 230 [-CHNO.] and m/z 186 [-C4H9NO.]; for QL A: C16H18N2O2 [M+H 271], which presented one ion at m/z 214, due to loss of fragment (-C4H9) from the molecular ion; and for QL D1: C16H18N2O3 [M+H 287], with product ions at m/z 186 [-CHNO] and m/z 230 [-C4H9]. Such data suggested fragmentation proposals, e.g. for Quinolactin B1 (Fig. 1), which confirmed the structures of the isolated quinolactins, and may represent an important contribution for the sustainable exploration of marine biodiversity.

Fig. 1: Quinolactin alkaloids from endophytic fungi Dm1 obtained from red alga Dichotomaria marginata and fragmentation proposal for Quinolactin B1

References:

[1] Cardozo, KHM et al. Comp Biochem Physiol C Toxicol Pharmacol 2007, 146, 60.

[2] Silva, GH et al. Phytochem. Lett. 2010, 3, 164.