Chlovalicin B, a Chlorinated Sesquiterpene Isolated from the Marine Mushroom Digitatispora marina.

Teppo Rämä,Espen H Hansen,Jeanette H Andersen,Marte Jenssen,Kumar Motiram-Corral,Johan Isaksson,Venke Kristoffersen,Kine Østnes Hansen

doi:10.3390/molecules26247560

Abstract

As part of our search for bioactive metabolites from understudied marine microorganisms, the new chlorinated metabolite chlovalicin B (1) was isolated from liquid cultures of the marine basidiomycete Digitatispora marina, which was collected and isolated from driftwood found at Vannøya, Norway. The structure of the novel compound was elucidated by spectroscopic methods including 1D and 2D NMR and analysis of HRMS data, revealing that 1 shares its molecular scaffold with a previously isolated compound, chlovalicin. This represents the first compound isolated from the Digitatispora genus, and the first reported fumagillin/ovalicin-like compound isolated from Basidiomycota. Compound 1 was evaluated for antibacterial activities against a panel of five bacteria, its ability to inhibit bacterial biofilm formation, for antifungal activity against Candida albicans, and for cytotoxic activities against malignant and non-malignant human cell lines. Compound 1 displayed weak cytotoxic activity against the human melanoma cell line A2058 (~50% survival at 50 µM). No activity was detected against biofilm formation or C. albicans at 50 µM, or against bacterial growth at 100 µM nor against the production of cytokines by the human acute monocytic leukemia cell line THP-1 at 50 µM.

Highlights

Fungi isolated from the marine environment have proven to be a promising source of novel bioactive compounds [1]
Marine fungi are under-explored compared to their terrestrial counterparts [1,2], and the studies of marine fungi have primarily focused on just a few genera; Penicillium, Aspergillus, and, in part, Fusarium and Cladosporium [1]
Digitatispora marina was isolated from driftwood of Betula (Figure S2) collected at Vannøya, Norway, in 2010 [8]

Summary

Introduction

Fungi isolated from the marine environment have proven to be a promising source of novel bioactive compounds [1]. The genus is one of the few genera of marine mushrooms and has been included in a number of phylogenetic studies. It has been placed in different orders, including Atheliales and Russulales [5,6]. In a survey from 2014, Rämä et al identified 28 filamentous species of marine fungi, with Digitatispora marina being the only basidiomycete [8]. As part of our ongoing search for novel bioactive metabolites from under-explored Arctic marine fungi, Digitatispora marina was selected for up-scaled cultivation and the isolation of its metabolites. The up-scaled culture was extracted and fractionated, and the fractions were analyzed using UHPLC-ESI-HRMS This led to the identification of a chlorinated compound. The cultivation of D. marina, as well as the extraction, isolation, and structure elucidation of 1, are described along with the evaluation of its antimicrobial, cytotoxic, and anti-inflammatory properties

Results and Discussion

General Experimental Procedures

Fungal Material and Cultivation Condition

Extraction and Isolation

Bioactivity Testing of Compound 1

Conclusions