New C15 Acetogenins from Two Species of Laurencia from the Aegean Sea.

Maria Harizani,Vassilios Roussis,Dafni-Ioanna Diakaki,Stamatios Perdikaris,Efstathia Ioannou

doi:10.3390/molecules27061866

Maria Harizani, Vassilios Roussis + Show 3 more

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https://doi.org/10.3390/molecules27061866

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Abstract

The chemical diversity of the approximately 1,200 natural products isolated from red algae of the genus Laurencia, in combination with the wide range of their biological activities, have placed species of Laurencia in the spotlight of marine chemists’ attention for over 60 years. The chemical investigation of the organic (CH2Cl2/MeOH) extracts of Laurencia microcladia and Laurencia obtusa, both collected off the coasts of Tinos island in the Aegean Sea, resulted in the isolation of 32 secondary metabolites, including 23 C15 acetogenins (1–23), 7 sesquiterpenes (24–30) and 2 diterpenes (31 and 32). Among them, six new C15 acetogenins, namely 10-acetyl-sagonenyne (2), cis-sagonenyne (3), trans-thuwalenyne C (4), tinosallene A (11), tinosallene B (12) and obtusallene XI (17), were identified and their structures were elucidated by extensive analysis of their spectroscopic data. Compounds 1–3, 5–11, 13 and 15–32 were evaluated for their antibacterial activity against Staphylococcus aureus and Escherichia coli.

Highlights

Red algae of the genus Laurencia can be found in temperate to tropical shores around the world, inhabiting littoral to sublittoral zones and spreading to depths down to 65 m
In the framework of our ongoing research on new bioactive natural products from the genus Laurencia, we investigated the chemical profiles of Laurencia microcladia Kützing and Laurencia obtusa (Hudson) Lamouroux, both collected off the coasts of Tinos Island in the Aegean Sea
A series of chromatographic separations of the organic extract of L. microcladia resulted in the isolation of 17 compounds (1–7, 11–12, 24–27 and 29–32), including nine C15 acetogenins (1–7 and 11–12), among which five are new natural products (2, 3, 4, 11 and 12), six sesquiterpenes (24–27, 29 and 30) and two diterpenes (31 and 32)

Summary

Introduction

Red algae of the genus Laurencia can be found in temperate to tropical shores around the world, inhabiting littoral to sublittoral zones and spreading to depths down to 65 m. The plasticity of their distinction markers has led to debates and frequent taxonomic revisions of the genus, which currently includes 137 accepted species [1]. Species of the genus Laurencia have been extensively investigated for over 60 years, resulting in the isolation of more than 1200 natural products, mainly sesquiterpenes, diterpenes, triterpenes and C15 acetogenins [2,3] They are still considered a fascinating source of new natural products, usually halogenated, that exhibit a variety of biological activities, including cytotoxic [4,5], antimicrobial [6], antiviral [7], antiparasitic [8], anti-inflammatory [9] and antifouling [10]. We report the evaluation of the antibacterial activities of compounds 1–3, 5–11, 13 and 15–32 against Staphylococcus aureus and Escherichia coli

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