Résumé:
phenolic compounds to study their antioxidant and antibacterial effects. The best phenolic
extract was tested to prevent sardine deterioration.
The extraction of polyphénols from leaves and bulbs was carried out by a conventional method (maceration) and the innovative one (microwave), using three solvent systems (acetone, ethanol, methanol) at 70%. We found that samples irradiated for three minutes gave the best yields.
For comparative purposes, total phenolics, flavonoïds and tannins are quantified from the different extracts. It found that leaves content is higher than that of bulbs. Extraction assisted by microwave, using acetone and ethanol, was best procedure of extraction of these bioactive compounds.
The antioxidant activity of selected extracts (FA, FA3, FE, FE3, BA, BE3) was evaluated by the means of three methods: FRAP method, DPPH essay and the β-carotene bleaching method. Results displayed that leaves extracts exercise notable antioxydant effect than the bulbs ones. The extract FA3 appears the best but less powerful than BHA which is used as standard.
A correlation between these extracts content’s of flavonoïds and antioxidant was highly significant (R2 > 0.95; p < 0.05) and even more significant than that obtained with total phenols and tannins.
Antibacterial potential of these extracts (FA, FA3, FE, FE3, BA, BE3) was tested by the Agar-well diffusion method against Bacillus subtilis ATCC6633, Staphylococcus aureus ATCC43300, Escherichia coli ATCC25922 and Pseudomonas aeruginosa ATCC27853. A moderate antibacterial activity of acetone extracts of leaves against Escherichia coli and Staphylococcus aureus was noted with a load of 1000 μg/disk.
The extract FA3 has been tested for its efficacy upon sardine with a concentration of 10, 25 and 50 mg/ml during 10 days of conservation at 6°C, using the TBARS method. The results showed that this extract reduce significantly the oxidation of sardine’s lipids.
