Investigation of essential oils of Conyza canadensis herb and root

Abstract

Canadian horseweed [Conyza canadensis (L.) Cronq.] is an Asteraceae species indigenous to America but it is distributed widely in Hungary. The aerial parts and the root of this plant have been used all over the word as a herbal medicine for gastrointestinal and rheumatic symptoms. Moreover, the volatile oil of horseweed have been applied for bronchitis and cystitis [1,2]. In order to evaluate chemical constituents and antimicrobial activities of horseweed, essential oils obtained from herbs and roots were investigated. The essential oils were analysed by combination of GC and GC/MS. The identification of the constituents was achieved from their retention indices and comparison of their MS data with computer library database and with literature data [3]. Both oils showed different chemical composition. The essential oil of the herbs contained more components than the essential oil of the roots. The major constituent of the oil of the aerial part of horseweed was limonene (78%), while main components of root oil were acetylenes. The antimicrobial activities of the oils were tested on Gram positive (Enterococcus faecalis, Staphylococcus aureus, Streptococcus pyogenes), Gram negative (Escherichia coli, Pseudomonas aeruginosa) bacteria, reference fungal strains and fungal strains isolated from patients (Candida, Cryptococcus, Trichophyton, Rhodotorula, Aspergillus). No substantial differences were found between the activities of the essential oils, none of them showed any activity against the bacterial strains tested, but exhibited moderate to strong activity against all fungi with the only exception of A. fumigatus. The highest zone of inhibition was observed against Cryptococcus neoformans.