Chemical profile and antibacterial activity of essential oils from leaves and fruits of Gaultheria procumbens L. cultivated in Poland

Essential oils (EOs) of Gaultheria procumbens were obtained by hydrodistillation with the yield of 1.30% ± 0.05 (v/dw) for leaves and 2.68% ± 0.08 (v/dw) for fruits. The GC-FID/MS analysis led to the identification of 64 volatile components, among which 27 were found in leaf EO, 49 in fruit EO, and 59 analytes were detected for the first time in G. procumbens. Methyl salicylate, which is known as a potent anti-inflammatory agent, was the dominant component making up to 97.5% and 99.8% of the total fruit and leaf EOs, respectively. The remaining volatiles of the leaves included mainly monoterpenes (α-pinene, β-pinene, limonene), methyl-o-anisate, massoilactone, spiro[4,5]decane-1-one, and aliphatic alcohols (heptan-2-ol, octan-1-ol), while the fruit EO contained apart from the dominant aliphatic and aromatic alcohols (benzyl alcohol, heptan-2-ol, p-cymen-7-ol) also carboxylic acids (3-hydroxyphenylacetic acid, heptanoic acid, octanoic acid) and aldehydes (hexanal, furfural, pent-4-enal). The antibacterial activity of the EOs was evaluated using a microdilution broth method against twelve reference strains, as well as clinical and environmental isolates. Differences between activity parameters of both EOs were not statistically significant (p > 0.05) for most tested bacteria. On the other hand, both EOs were significantly more effective against Gram-negative (MIC, 8.2-10.0 mg/mL) than Gram-positive bacteria (MIC, 13.5-16.7 mg/mL). Leaves and especially fruits of G. procumbens cultivated in Poland were proved valuable sources of methyl salicylate-rich EOs of moderate antibacterial activity, which, therefore, could partly explain the traditional use of the plant materials and the EOs in the treatment of bacterial infections-related inflammatory disorders.