Chemical profile and antimicrobial activity of Leonotis nepetifolia (L.) R. Br. essential oils

Abstract

Leonotis nepetifolia (L.) R. Br. (Lamiaceae) is a naturalised medicinal plant in Brazil known as 'cordão-de-frade', being used in folk medicine for the treatment of a variety of conditions such as infections and inflammations. L. nepetifolia leaf and flower essential oils were isolated by hydrodistillation, and their compounds were identified by GC-MS analysis. The leaf essential oil major constituents were germacrene D (31.5%), and β-caryophyllene (19.2%), while in flower essential oil the main constituents were β-elemene (31.2%), and germacrene D (12.1%). The essential oils were investigated against a broad spectrum of bacteria and fungi using the microdilution method, exhibiting MIC₅₀ values of 3.93-250 µg mL^-1. Both oils showed excellent antifungal properties, which is a very important finding since most fungi have shown increased resistance to known antifungal agents. According to these results, the essential oils of L. nepetifolia are promising sources of new antimicrobial agents, especially for yeast.

Keywords: Essential oil; GC-MS; Lamiaceae; Leonotis nepetifolia; antimicrobial.