Halogenated Diterpenes with In Vitro Antitumor Activity from the Red Alga Sphaerococcus coronopifolius.

Vangelis Smyrniotopoulos,Emídio Vasconcelos Leitão Da Cunha,Anna Cláudia De Andrade Tomaz,Vassilios Roussis,Véronique Mathieu,Maria De Fátima Vanderlei De Souza,Efstathia Ioannou,Robert Kiss

doi:10.3390/md18010029

Abstract

Eight new (1–8) structurally diverse diterpenes featuring five different carbocycles were isolated from the organic extracts of the red alga Sphaerococcus coronopifolius collected from the coastline of the Ionian Sea in Greece. The structures of the new natural products, seven of which were halogenated, and the relative configuration of their stereocenters were determined on the basis of comprehensive spectroscopic analyses, including NMR and HRMS data. Compounds 5 and 8 were found to possess in vitro antitumor activity against one murine and five human cancer cell lines with mean IC50 values 15 and 16 μM, respectively.

Highlights

Nature has generously offered a plethora of chemical structures that have as such been used as therapeutics or have inspired the development of new pharmaceuticals
S. coronopifolius specimens were collected by scuba diving from Ai Giannis Bay (Parga, Greece) and the freeze-dried algal fronds were extracted with CH2 Cl2 /MeOH to afford an oily residue that was subjected to a series of chromatographic separations, including a combination of vacuum and flash column chromatography over silica gel and repeated C18 reversed and normal phase HPLC
In our continuing investigation aimed at the bioactivity screening and isolation of bioactive metabolites from the Greek seas, eight new structurally diverse halogenated diterpenes (1–8) were isolated from the red alga S. coronopifolius

Summary

Introduction

Nature has generously offered a plethora of chemical structures that have as such been used as therapeutics or have inspired the development of new pharmaceuticals. One of the most primitive forms of life, biosynthesize secondary metabolites with broad structural diversity. A considerable number of these natural products are halogenated, as a consequence of the abundance of halogen ions in the seawater. 300 in the seawater) seems to enhance the bioactivity of compounds, while on the other hand, iodinated chemical structures are rare among secondary metabolites [1]. Mar. Drugs 2020, 18, 29; doi:10.3390/md18010029 www.mdpi.com/journal/marinedrugs

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