Phytochemistry, Antimicrobial, and Antibiofilm Properties of Malagasy Helichrysum manopappoides Essential Oil

<i>Helichrysum</i> Mill. is one of the largest genera in the Asteraceae family, and in Madagascar, a plant paradise with ca 14,000 species, 111 <i>Helichrysum</i> species are known, 110 of which are endemic. In this work, the essential oil of endemic <i>Helichrysum manopappoides</i> Humbert, obtained by steam distillation, was investigated chemically and biologically. The spectrometric data obtained by GC-MS (Gas Chromatography-Mass Spectrometry) analysis highlighted the presence of three major compounds, such as eucalyptol (7.38 ± 0.36%), <i>α</i>-humulene (14.75 ± 0.79%), and <i>β</i>-caryophyllene (19.78 ± 0.89%), which were also structurally confirmed by NMR (Nuclear Magnetic Resonance) spectroscopic investigation. Biological results showed potential antimicrobial, antioxidant, and antibiofilm effects of both the <i>H manopappoides</i> essential oil and the main components identified by GC-MS, enhancing an interesting approach for intestinal infections, being active against <i>Escherichia coli</i>, <i>Listeria monocytogenes</i>, <i>Shigella sonnei</i>, and <i>Salmonella enterica</i> ser. <i>typhimurium</i> strains.