Investigation of the marine microorganism Cladosporium halotolerans for the isolation and identification of bioactive metabolites with potential anti-aging activity

The marine environment is an inexhaustible source of secondary metabolites with significant biological activities. In continuation of our efforts to discover bioactive metabolites from under-investigated marine environments[ ¹ ], invertebrates and their associated microorganisms were collected from areas of the mesophotic zone of the Red Sea that were found to be rich in biodiversity. More than 100 microorganisms were cultivated under solid and liquid conditions, and evaluated for their potential anti-aging activity using elastase and tyrosinase enzymatic assays. In the context of this work, the strain ΧΜLm 133-S2, isolated from Sarcophyton sp., a soft coral collected from the Red Sea, was selected for further investigation since it exhibited a promising effect in elastase and tyrosinase enzymes.

The strain, identified as Cladosporium halotolerans, was re-cultivated under liquid conditions (10L scale) in marine broth using absorption resin technology and extracted with AcOEt and MeOH. Dereplication techniques were employed in order to investigate the metabolite content in each extract and the isolation of secondary metabolites was performed using different chromatography techniques (CPC, Semi-Prep HPLC, Sephadex LH-20, Prep-TLC). Spectroscopic and spectrometric data (1D & 2D NMR and UPLC-HRMS) were recorded for all isolated compounds, in order to refunambiguously elucidate their structure. In total, eighteen compounds were elucidated. Bioevaluation of isolated compounds shown that among them, six diketopiperazines from AcOEt extract and a nucleoside from MeOH extract displayed remarkable inhibitory activity against elastase or tyrosinase.

• References

• 1 Vlachou. et al. Innovative approach to sustainable marine invertebrate chemistry and a scale-up technology for open marine ecosystems. Mar Drugs 2018; 16 (05) : 152. DOI: https://doi.org/10.3390/md16050152.