Chemical composition and antimicrobial activities of essential oil extracted from Tithonia diversifolia (Asteraceae) flower

Abstract

The upsurge in the prevalence of side effects of many synthetic antimicrobial agents and incidence of multidrug resistant bacteria has spurred scientists on the search for plant based antimicrobial of therapeutic potentials. The study extracted essential oils from the flowers of Tithonia diversifolia (Hemsl) A. Gray (Mexican sunflower) and assayed it for antimicrobial activities. The oils were extracted (hydro-distillation), characterized (GC-MS) and tested for antibacterial and antifungal activities. α-Pinene (34.42%), β-Caryophyllene (22.34%), β-Pinene (11.14%), Germacrene-D (11.13%) and 1, 8-Cineole (8.76%) were the major constituents of the forty-five compounds characterized. The characterized compounds were general monoterpenes (44.44%), sesquiterpenes (26.67%), including alcohols and aldehydes which accounted for 28.89%. The extract concentrations of 8-120 mg/ml in Potato Dextrose Agar (PDA) medium effectively inhibited the tested fungi in vitro . At 5 mg/ml, only Bacillus megaterium and Bacillus cereus were inhibited of all gram-positive bacteria while Streptococcus pyrogens was unaffected. All gram-negative bacteria were inhibited. Growth inhibition of the gram-positive and gram-negative species increases with increased concentration of the essential oil. At 40 mg/ml, all the tested bacteria species were inhibited and the growth inhibition for the species followed the order; E. coli> Proteus mirabi> Bacillus megaterium> Klebsiella pneumonia> Bacillus cereus> Streptococcuspyrogens . The oil concentration of 72 mg/ml totally inhibited the growth of all three fungal species - Cochliobolus lunatus , Fusarium solani , Fusarium lateritum. The secondary metabolites in the oil of T. diversifolia proved effective against the tested bacteria and fungi species. The finding of this study unlocks the potentials of this essential oil of Mexican sunflower for bio-pesticide production.