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.