Chemical composition and evaluation of antimicrobial and antioxidant activities of essential oils from Lippia hermannioides and Matayba marginata, two plants on ironstone outcrops: an endangered Brazilian ecosystem

Canga is the Brazilian term used to describe a weathered superficial ferruginous deposit. These geoenvironments shelter hundreds of rare species. Essential oils of Lippia hermannioides and Matayba marginata, species collected in the ferruginous rupestrian field on remaining canga at Federal University of Ouro Preto-UFOP, were isolated from fresh leaves by hydrodistillation in a Clevenger-type apparatus and characterized by GC-MS analyses. A total of 32 compounds were identified in the oil of L. hermannioides, while 15 were identified in the oil of M. marginata, representing 98.9% and 97.7% respectively, of the total volatile content. In both essential oils sesquiterpene hydrocarbons were the main class of constituents (53.4% for L. hermannioides and 92.1% for M. marginata). Elemicin (35.1%) and β-caryophyllene (21.3%) were found to be the major constituents in the essential oil of L. hermannioides, whereas germacrene A (48.8%) and β-elemene (29.5%) were encountered in the essential oil of M. marginata. Both essential oils showed bactericidal activity against Gram-positive bacteria, with the essential oil of L. hermannioides being more efficient. The oils did not present antioxidant activity and by ORACFL assay. The oil of L. hermannioides showed weak DPPH radical-scavenging activity by thin-layer chromatography (TLC) autographic assay. The data presented in this study showed, for the first time in literature, the chemical composition of essential oil from M. marginata and their bactericidal and antioxidant properties. These findings contribute to the knowledge of the chemical composition and biological activities of Lippia and Matayba genera.