Chemical Study and Comparison of the Biological Activities of the Essential Oils of Helichrysum petiolare, H. cymosum, and H. odoratissimum

Helichrysum species are prominent South African medicinal plants. From the essential oils (EOs) of three Helichrysum species, H. petiolare, H. odoratissimum, and H. cymosum, sixty-three constituent components were identified, with hydrocarbons and oxygenated monoterpenes and sesquiterpenes as major components. The compounds were analyzed by gas chromatography-mass spectrometry (GC-MS) and nuclear magnetic resonance (NMR) spectroscopy. In H. petiolare EO, the major components were faurinone (20.66%) and (E)-β-ocimene (17.21%). Faurinone was isolated from this EO for the first time. In H. odoratissimum, 1,8-cineole (17.44%) and α-pinene, and γ-curcumene (15.76%) were the major components whereas, in H. cymosum, α-pinene (29.82%) and (E)-caryophyllene (19.20%) were the major components. In the antibacterial activity study, the EOs were tested against Staphylococcus aureus, Escherichia coli, and Pseudomonas aeruginosa. The EOs were found to possess low antibacterial, anti-tyrosinase, and photoprotection activities and moderate antioxidant capacities, thus establishing these Helichrysum EOs as valuable antioxidant agents.