Chemotype analysis and antimicrobial activities of essential oils from fresh and sun-dried berries of piper guineense (Schum. and Thom)

Abstract

Chemical constituents of the essential oils obtained through hydrodistillation from fresh and sun-dried berries of Piper guineense were determined through gas chromatography/flame ionization detection (GC/FID) together with gas chromatography/mass spectrometry (GC/MS) techniques. The antimicrobial activities were evaluated through agar diffusion method. The oil yields from the dried berries (1.42 % v/w) was higher than 1.10 % from fresh berries. Chemical profile of oils showed 61 compounds which accounted for 99 % of the total oils′ content. Essential oil from fresh berries consisted mainly of α-fellandrene (26.32 %), δ-3-carene (16.63 %) and β-pinene (9.89 %). Dried berries oil was composed of β-linalool (11.96 %), β-pinene (7.82 %), caryophyllene (7.65%), α-pinene (7.11%), 3-carene (5.38 %), β-bisabolene (5.11 %) and β-copaene (4.16 %). The essential oil from dried berries had higher sesquiterpenes while the fresh berries had more of monoterpene hydrocarbons. The higher sesquiterpene content of oil from dried berries may be attributed to the loss of monoterpenes through drying, while higher alcohol may be as a result of aerial oxidation of some constituents. Essential oils from dried berries had a more inhibition effect on Gram-positive bacteria (Staphylococcus aureus), Gram-negative bacteria (Escherichia coli) and two fungi species: Candida albicans and Aspergillus flavus compared to fresh berries extract. These findings suggest that sun-drying as preservation method may enhance the antimicrobial activity of Piper guineense.