Dereplication strategies for targeted isolation of new antitrypanosomal actinosporins A and B from a marine sponge associated-Actinokineospora sp. EG49.

Usama Ramadan Abdelmohsen,Christina Viegelmann,Ruangelie Edrada-Ebel,Tanja Grkovic,Safwat Ahmed,Cheng Cheng,Tong Zhang,Ute Hentschel,Ronald J Quinn

doi:10.3390/md12031220

Abstract

High resolution Fourier transform mass spectrometry (HRFTMS) and nuclear magnetic resonance (NMR) spectroscopy were employed as complementary metabolomic tools to dereplicate the chemical profile of the new and antitrypanosomally active sponge-associated bacterium Actinokineospora sp. EG49 extract. Principal Component (PCA), hierarchical clustering (HCA), and orthogonal partial least square-discriminant analysis (OPLS-DA) were used to evaluate the HRFTMS and NMR data of crude extracts from four different fermentation approaches. Statistical analysis identified the best culture one-strain-many-compounds (OSMAC) condition and extraction procedure, which was used for the isolation of novel bioactive metabolites. As a result, two new O-glycosylated angucyclines, named actinosporins A (1) and B (2), were isolated from the broth culture of Actinokineospora sp. strain EG49, which was cultivated from the Red Sea sponge Spheciospongia vagabunda. The structures of actinosporins A and B were determined by 1D- and 2D-NMR techniques, as well as high resolution tandem mass spectrometry. Testing for antiparasitic properties showed that actinosporin A exhibited activity against Trypanosoma brucei brucei with an IC50 value of 15 µM; however no activity was detected against Leishmania major and Plasmodium falciparum, therefore suggesting its selectivity against the parasite Trypanosoma brucei brucei; the causative agent of sleeping sickness.

Highlights

Dereplication refers to the rapid identification of known secondary metabolites and their quantification in crude unfractionated extracts [1,2,3]
Dereplication of the secondary metabolites from the antitrypanosomally active isolate Actinokineospora sp. strain EG49 was achieved by high resolution Fourier transform mass spectrometry (HRFTMS) using the Exactive-Orbitrap and high resolution nuclear magnetic resonance (NMR)
Secondary metabolites were tentatively identified with the aid of existing high resolution MS and NMR records from online and in-house databases, i.e., MarinLit, a database for marine natural products and AntiBase, a database of microbial secondary metabolites

Summary

Introduction

Dereplication refers to the rapid identification of known secondary metabolites and their quantification in crude unfractionated extracts [1,2,3]. The large data set produced by NMR and MS experiments requires multivariate analysis for data interpretation, such as principal component analysis (PCA), hierarchical clustering analysis (HCA), and orthogonal partial least square-discriminant analysis (OPLS-DA) [5]. Application of these analytical and statistical methods in metabolomics, facilitates the discovery of potentially novel microbial secondary metabolites as well as the bioassay-guided isolation work [1,2,6,7,8,9,10,11,12]. By using combinations of different analytical methods, the bioassay-guided isolation route is shortened and putative identification of potentially new natural products is rapidly achieved [3,14]

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Conclusion