Chemical Composition and Biological Activities of Santiria trimera (Burseraceae) Essential Oils from Gabon

Water-distilled essential oils from leaves and bark of Santiria trimera (Oliv.) Aubrév. (Burseraceae) collected in Gabon were analyzed using capillary GC-FID and GC-MS. The leaf essential oil, which is described for the first time, was dominated by sesquiterpenes (76.5%), among which α-humulene (34.6%) and β-caryophyllene (14.9%) were the major components. The bark essential oil was almost exclusively monoterpenic, with α-pinene (51.5%) and α-terpineol (16.8%) as main constituents. The antimicrobial activities of both essential oils were tested against eight Gram-positive and three Gram-negative bacteria by using agar disc diffusion and broth microdilution methods; anticandidal effect was also tested on different strains of Candida albica. The Gram-negative bacteria were the less sensitive to the leaf essential oil, which was effective against Bacillus cereus and Enterococcus faecalis. The bark essential oil was more active and, in particular, exhibited significant antimicrobial activity against Proteus mirabilis, which was resistant to the leaf oil. A weak anticandidal effect of both essential oils was observed.