RESUMO
Objective: The aim of this study was to determine the chemical characteristics and antibacterial activity of Fontitrygon margarita liver oil against the bacteria responsible for food poisoning. Methods: Oils were extracted from F. margarita liver using two methods (exudation and cooking-pressing) and analyses by Fourier transform infrared (FTIR) spectroscopy. Quality indexes were determined using standard methods and the fatty acid profile was carried out by gas chromatography with a flame ionization detector (GC-FID). Antibacterial activities of these oils, their emulsion, and their interactions with common antibiotics were evaluated by the broth microdilution method. Results: Extraction yield was higher with cooking-pressing (16.90%) compared to exudation (14.49%). The quality indexes of both oils were conformed to Codex Alimentarius Standard. Thiobarbituric acid index was higher with exudation compared to cooking-pressing (3.20 ± 0.14 and 2.36 ± 0.14 µmol MDA/kg, respectively) while acid, iodine, peroxide, and anisidine values did not significantly vary with the extraction methods (2.15-2.30 mgKOH/g, 102.42-106.65 gI2/100 g, 3.34-3.57 meqO2/kg, and 2.85-3.32 respectively). FTIR analyses clearly show that the two spectra are similar (no differences in the frequency and absorbance of their bands). The fatty acid profile revealed that, regardless of the extraction methods, F. margarita oil is richer in monounsaturated (55.97-55.41%) followed by polyunsaturated (28.17-28.52%) and saturated fatty acids (15.86-16.07%). Moreover, these oils showed antibacterial activity on all the bacteria strains tested with MICs between 16 and 256 mg/ml. Regardless of the extraction methods, emulsions showed higher activity (6.25 ≤ MIC ≤25 mg/ml) compared to crude oils. Additionally, F. margarita liver oil potentiated the antibacterial activity of ciprofloxacin, tetracycline, gentamicin, amoxicillin, and chloramphenicol. Conclusion: These results showed the effectiveness of Fontitrygon margarita liver oil against some bacteria responsible for food poisoning, thus demonstrating their antibacterial properties which could be due to their chemical composition.
RESUMO
BACKGROUND: Enantia chlorantha is a plant belonging to Annonaceae Family. The Barks and leaves are used traditionally to treat infectious diseases. Earlier studies highlighted the antibacterial activity of stem barks methanol extract. This study is thus aimed at investigating the effect of fractionation on antibacterial activity of its n-butanol fraction. METHODS: The extract of E. chlorantha stem barks was obtained by maceration in methanol and then subjected to a liquid/liquid partition by successive depletion with solvents of increasing polarity. The n-butanol fraction was fractionated by adsorption chromatography on silica gel. A product was isolated from the dichloromethane/methanol (2%) fraction and the structure was determined on the basis of spectroscopic data; Proton Nuclear Magnetic Resonance (1H NMR), Carbon-13 Nuclear Magnetic Resonance (13C NMR), Heteronuclear Multiple Bond Correlation (HMBC), H-correlation spectroscopy (H-COSY), attached proton test (APT), heteronuclear multiple quantum coherence (HSQC). The antibacterial activity was evaluated by broth microdilution method against six reference strains and eight clinical bacterial strains. RESULTS: The n-butanol fraction was found to be active with MIC values ranging from 32 to 256 µg/mL. The FA sub-fraction was more efficient among the eight sub-fractions, the n-butanol fraction and comparable to Chloramphenicol used as reference antibiotic. The product obtained was elucidated as palmitin. The antibacterial activity of the latter was comparable to that of Chloramphenicol on one reference strain and 4 of the 6 clinical strains. CONCLUSION: The FA sub-fraction had better antibacterial activity than the n-butanol fraction and other sub-fractions, and possibly palmitin was the active substance responsible for the antibacterial activity of E. chlorantha.