Antibacterial Activity and Anxiolytic Effect in Adult Zebrafish of Genus Lippia L. Species.

Species belonging to the genus Lippia are used worldwide as foods, beverages, and seasonings. Studies have demonstrated that these species have antioxidant, sedative, analgesic, anti-inflammatory, and antipyretic activities. This work aimed to evaluate the antibacterial activity and anxiolytic effect by different pathways of essential oils and ethanolic extracts of three species of Lippia (Lippia alba, Lippia sidoides, and Lippia gracilis). The ethanolic extracts were characterized by HPLC-DAD-ESI-MSn and their phenolics were quantified. The antibacterial activity was evaluated by determining the minimal inhibitory concentration and modulation of antibiotic activity, and toxic and anxiolytic effects were evaluated in the zebrafish model. The extracts showed compositions with a low ratio and shared compounds. L. alba and L. gracilis showed higher amounts of phenols and flavonoids, respectively. All extracts and essential oils presented antibacterial activity, especially those obtained from L. sidoides. On the other hand, L. alba extract presented the most significant antibiotic-enhancing effect. The samples were not toxic after 96 h of exposure, but showed an anxiolytic effect through modulation of the GABAA receptor, while L. alba extract acted via modulation of the 5-HT receptor. This new pharmacological evidence opens horizons for therapeutic approaches targeting anxiolytic and antibacterial therapies and food conservation using these species and their constituents.

In vitro inhibition of a multispecies oral cavity biofilm by Syzygium aromaticum essential oil.

OBJECTIVE: To evaluate the anti-fungal activity of Syzygium aromaticum essential oil and its inhibition of a multispecies biofilm in patients with oral candidiasis. BACKGROUND: Inhibiting biofilm formation on the denture surface is an important practice for preventing denture stomatitis. MATERIALS AND METHODS: The anti-fungal activity against Candida albicans and non-albicans Candida species was evaluated through the microdilution method to define Minimal Inhibitory (MIC) and Fungicidal (MFC) Concentrations. Time-kill assay assessed growth kinetics of C. albicans based on pre-determined time points (0, 1, 2, 4, 6 and 24 hours). A multi-species biofilm was formed using human saliva from patients with oral candidiasis and anti-biofilm activity determined by Colony Forming Units per milliliter (CFU/mL) count, fluorescence microscopy with calcofluor white to observe yeast presence and structure, and metabolic activity by XTT (2,3-Bis-(2Methoxy-4-Nitro-5-Sulfophenyl)-2H-Tetrazolium-5-carboxanilide) reduction assay. RESULTS: The essential oil showed an anti-fungal activity against all Candida species (MIC 500-1000 µg/mL, MFC 1000-2000 µg/mL), and the time-kill assay showed that 2000 µg/mL (from 2 hours onward) and 1000 µg/mL (from 4 hours onward) concentrations had substantially lower yeast growth than the negative control. In the biofilm analysis, the essential oil had a lower CFU/mL count and a biofilm metabolic activity (91.4%) than seen with its negative control, and in both analyses, the essential oil was not significantly different from the positive control (chlorhexidine). Morphological analysis showed amorphous and fragmented cellular structures after treatment with the essential oil. CONCLUSION: Syzygium aromaticum essential oil had anti-fungal activities, reduced the Candida growth kinetics substantially and inhibited the multi-species biofilm formation.