Résumé:
The aim of this study was to determine the chemical composition of pepper and evaluate its biological properties. The profile of polyphenols was determined with a developed LC-MS method, the derivatives of quercetin, kaempferol and rutin ( 113.46, 30.86 and 18.30 μg/g respectively) were the major compounds. For the study of capsaicinoïds, an extraction method was optimized. After identification, it appeared that capsaïcin and dihydrocapsaïcin represent 59.83% and 33.12% of the total capsaicinoïds. The placenta was the major site of capsaicinoïds followed by seeds then the pericarp. After identification of carotenoids of peppers, lutein was found to represent 54.40% of total carotenoids (13.42 μg/g), Zeaxanthin (17.53%; 4.32 μg/g) and b-carotene (17.03%; 4.20 μg/g). The antioxidant activity of the three extracts (polyphenols, capsaicinoïds and carotenoids) was evaluated with DPPH, ABTS and FRAP tests. According to the results, carotenoids are the most powerful antioxidants compared to polyphenols and capsaicinoïds (2.78, 0.052 and 0.050 mM Te/g), (3.379, 0.069 and 0.065 mM Te/g) and (5.885, 0.109 and 0.094 mmol Fe2+ e/g) respectively. The antimicrobial activity of the polyphenols, capsaicinoïds and the main identified compounds was investigated. Caffeic acid, quercetin and kaempferol were the most actives with MICS values range of (0.25-2 mg/ml), (0.00195-0.5 mg/ml) and (0.0078- 0.25 mg/ml) respectively. In order to see if a possible synergy exists between these phenolic compounds, the FIC index was calculated with a gram positive strain Staphylococcus aureus ATCC 6538P and another gram negative Pseudomonas aeruginosa ATCC 27853. The best combination for S. aureus was caffeic acid and quercetin (FIC=0.37), quercetin and kaempferol for P. aeruginosa (FIC=0.31). The cytotoxicity of the polyhenols, capsaicinoïds and carotenoids of pepper was evaluated against PBMCs and U937 cell lines. The carotenoids had the highest antitumoral effect with a decrease of 41.74% of U937 at only a concentration of 25 μg/mL, but the phenolic extract had the most selective effect.
