This study was initiated to evaluate the chemical composition and in vitro antimicrobial activity of essential oils from four Cameroonian spices and to determine the therapeutic effect of a cream based on essential oil from Aframomum citratum. Essential oils were extracted from seeds by hydrodistillation and analyzed by gas chromatography coupled with mass spectrometry (GC/MS). The broth microdilution method was used for the minimum inhibitory concentration (MIC) and minimum microbicidal concentration (MMC) determinations. The therapeutic effect of a cosmetic cream based on essential oil from A. citratum seed (1.25, 2.5 and 5% w/w) was evaluated against dermatosis induced with a Methicillin-Resistant Staphylococcus aureus (MRSA) in rats. The main identified compounds in the essential oils are geraniol for A. citratum; eucalyptol, α-terpineol and geraniol for Aframomum daniellii; β-pinene, germacrene D, trans-β-caryophyllene, α-pinene, naphthalene and sabinene for Piper capense; α-phellandrene, germacradienol and δ-cadinene for Monodora myristica. Essential oil of A. citratum (MIC = 8-4096 µg/ml) was the most active against bacteria and fungi, following in decreasing order by those of A. daniellii, P. capense and M. myristica. The antibacterial activity of the essential oil of A. citratum against MRSA and Escherichia coli S2(1) (MIC = 8 µg/ml) was higher than that of amoxicillin used as reference drug (MIC = 128- 256 µg/ml). The combination of essential oils of A. citratum and A. daniellii (1:1) displayed a synergistic effect. The cream based on essential oil of A. citratum (5%) and Baneocin (reference drug) eradicated the dermatosis induced with MRSA in rat after two weeks of treatment. These results indicate that the tested essential oils possess antimicrobial activities which could be a function of either the individual or the additive effects of the identified phytoconstituents.
Key words: Spices, hydrodistillation, essential oils, gas chromatography/mass spectrometry (GC/MS), antibacterial, antifungal, synergistic effect.
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