Asterisulphoxide and asterisulphone: two new antibacterial and antifungal metabolites from the Tunisian Asteriscus maritimus (L.) Less

Abstract

Two new sulphur-containing metabolites, asterisulphoxide 1 and asterisulphone 2, together with six known compounds, coniferaldehyde 4, 4-hydroxy-2-methoxybenzaldehyde 3, methylcaffeate 5, isobutyrate 10-isobutyryloxy-8,9-epoxythymyle 6, 8,9-dihydroxy-10-isobutyryloxythymol 7 and 8-hydroxy-9,14-diisobutyryloxythymol 8, were isolated from Asteriscus maritimus roots. Their structures were elucidated on the basis of spectroscopic evidence and comparison with authentic samples. Compounds 1–8 were assessed for their in vitro antibacterial activity against Pseudomonas aureofasciens, Burkholderia glathei, Bacillus pumilus and their antifungal effects against Aspergillus flavus, Aspergillus niger, Penicillium digitatum, Botrytis cinerea and Fusarium oxysporum f. sp. lycopersici, using the disc diffusion method (20 μL/disc). A remarkable inhibition zone 10–15 mm of the growth of the bacterial and fungal agents was observed. The obtained results suggest that the isolated compounds could be promising abiotic antimicrobial agents.

Keywords::

• Asteriscus maritimus
• asterisulphoxide
• asterisulphone
• antibacterial activity
• antifungal activity

Acknowledgement

The authors are grateful to Prof. Bouzid Nasraoui, The National Agronomic Institute of Tunisia, for providing the bacterial strains used in the antibacterial test.