Investigation of optimal methods including pH-zone-refining centrifugal partition chromatography for the isolation of communesins from cultures of a marine-derived Penicillium expansum

Communesins are a rare family of indole alkaloids isolated from marine or terrestrial fungal strains [1]. To date, eleven communesins (A-K) have been described, which share a common and unique heptacyclic core with the presence of two vicinal quaternary centres [2]. Recently, 10 new analogs have been detected by HPLC-HRMS/MS as trace-amounts in cultures of a P. expansum marine-derived strain [3]. Very few biological data have been described for this class of compounds, but an interesting activity on the cellular cytoskeleton has been once described, making them a putative new class of microfilament disrupting drugs [4]. In this context, our laboratory has engaged a program for the investigation of communesin chemodiversity and structure-activity relationships. The aim of this study was: 1- to obtain the major compounds communesin A and B in sufficient quantities for their pharmacological evaluation, and 2- to investigate the use of pH-zone-refining Centrifugal Partition Chromatography (CPC) for the isolation of minor communesin analogs. Different methods of extraction and purification were then tested and the composition of the fractions obtained was established by UHPLC-ESI-MS/MS. This led to the development of an optimized protocol including a solvent culture extraction followed by an indole alkaloid concentration at pH 1, allowing the selective recovery of communesins with a yield of 98%. 70 mg and 52 mg of communesin A and B respectively were then obtained as pure compounds. The alkaloidic fraction was subsequently fractionated by pH-zone-refining CPC in ascending mode using a biphasic solvent system composed of methyl tert-butyl ether/acetonitrile/water (4/1/5, v/v/v). The separation of more than ten communesins was then performed, which were further purified. Then, pH-zone refining CPC was shown to be an efficient separation tool for fungal alkaloids isolation, which will allow to reveal the structural diversity of this unique class of complex natural products.

Acknowledgements: Authors acknowledge the Vietnam International Education Development program for a PhD grant for Thuy T.P. Hoang.

Keywords: Communesin, Penicillium expansum, centrifugal partition chromatography (CPC).

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