Anticandidal and synergistic effect of essential oil fractions from three aromatic plants used in Cameroon.

Despite the use of conventional antifungal drugs, Candida spp resistance, especially mediated by biofilms formation remains recurrent. Therefore, new drugs to treat fungal infections are urgently needed. In this line, our study aimed to determine the anticandidal activity and the synergistic effect of essential oil fractions from Syzygium aromaticum, Cymbopogon citratus and Aeollanthus heliotropioides harvested in Cameroon using a combination approach. Essential oils have been obtained by hydrodistillation and their chemical composition was analysed by GC/MS. Antifungal activity was evaluated by the determination of minimum inhibitory concentration (MIC) using a micro-dilution method. The sorbitol and ergosterol binding ability and anti-biofilm activity were also assessed in order to evaluate the mode of action. The crude essential oils showed a good anticandidal activity, most probably due to the eugenol, linalool and citral content. The combination of two fractions F7 and F10 showed an improved growth inhibition of Candida spp compared to the crude essential oils. The inhibitory effect could be related with the presence of γ-dodecalactone and citronellol as main compounds. The best synergistic combination F7F10 inhibited biofilm formation at ten time reduced combination MIC. The active fractions targeted different fungal cell structures, including cell wall and membrane. Our study showed that the combination of selected essential oils fractions exhibited an increased antifungal activity against Candida spp compared to the crude essential oils. The combination approach of inner compound groups may be used as a promising strategy for the development of efficient recombined micro-essential oils as antifungal agents to face Candida resistance.

Synthetic flavonoids with antimicrobial activity: a review.

The emergence of drug-resistant microbes left us with a great need for new antimicrobial agents. Flavonoids, with their wide range of biological activities, are good candidates in this respect. Although naturally occurring flavonoids are the most studied ones, semi-synthetic or synthetic flavonoids have proven to have great potential, inhibiting and even killing microbes at concentrations below 1 µg ml-1 . The substitution pattern of these flavonoids often includes hydroxy groups, halogens or other heteroatomic rings, such as pyridine, piperidine or 1,3-dithiolium cations. However, the great variety in substituents makes it difficult to draw any definitive conclusion regarding their structure-activity relationship.

Antibacterial activity and proposed action mechanism of a new class of synthetic tricyclic flavonoids.

AIMS: This study reports on the inhibitory and bactericidal properties of a new synthetized flavonoid. METHODS AND RESULTS: Tricyclic flavonoid 1 has been synthesized through a two-step reaction sequence. The antimicrobial effects were tested using the minimum inhibitory concentration (MIC) and minimum bactericidal concentration (MBC) assays. Also DNA fragmentation assay, fluorescence microscopy and SEM were used to study the mechanism of action. Our tested flavonoid displayed a strong antimicrobial activity with MIC and MBC values as low as 0·24 µg ml(-1) against Staphylococcus aureus and 3·9 µg ml(-1) against Escherichia coli. Flavonoid 1 displayed antimicrobial properties, causing not only the inhibition of bacterial growth, but also killing bacterial cells. The mechanism of action is related to the impairment of the cell membrane integrity and to cell agglutination. CONCLUSIONS: Tricyclic flavonoid 1 was found to have a stronger antibacterial effect at lower concentrations than those described in the earlier reports. SIGNIFICANCE AND IMPACT OF THE STUDY: Based on the strong antimicrobial activity observed, this new tricyclic flavonoid has a good potential for the design of new antimicrobial agents.