Application of Doehlert Experimental Design for Optimization of a New-Based Hydrophilic Interaction Solid-Phase Extraction of Phenolic Acids from Olive Oils.

In this work, a rapid, precise, and cost-valuable method has been established to quantify phenolic compounds in olive oil using new-based hydrophilic interaction solid-phase extraction (SPE). Boehlert's experimental design applied the determination of the optimal operating conditions. An investigation into the effects of the methanol composition (50-100%), the volume of eluent (1-12 mL), and pH (1-3) on the extraction of phenols acids and total phenols from Tunisian olive oils was performed. The results showed that the extraction conditions had a significant effect on the extraction efficiency. The experiment showed that the greatest conditions for the SPE of phenolic acids were the methanol composition at 90.3%, pH at 2.9, and volume at 7.5 mL, respectively. The optimal conditions were applied to different types of olive oils, and it could be concluded that larger concentrations of polyphenols were found in extra virgin olive oil (89.15-218), whereas the lowest levels of these compounds (66.8 and 5.1) were found in cold-pressed crude olive oil and olive pomace oil, respectively.

Antioxidant, Antimicrobial and the Phenolic Content of Infusion, Decoction and Methanolic Extracts of Thyme and Rosmarinus Species.

BACKGROUND: The plant species Rosmarinus officinalis (RO), Thymus algeriensis (TA) and Thymus capitatus (TC) are widely used in traditional medicine in Tunisia. Their bioactivities have been reported before and particularly referred to their essential oils. The main objective of this work was to assess the phytochemical composition, the antioxidant activity, the antibacterial, antifungal, and cytotoxic potential of these 3 plants. METHOD: The High Performance Liquid Chromatography (HPLC), chemical tests and spectrophotometric methods were used for screening, quantification of phytochemicals and for antioxidant activities. Extracts were evaluated for antibacterial potential by the microdilution method. Antifungal activities were tested using the Poisoned food method against: Aspergillus niger and Aspergillus flavus. The cytotoxic potential of the plant extracts was checked using HCT 116 cultures. RESULTS: Results revealed that aqueous extracts are not toxic compared to the methanolic extracts. Phenolic compounds were detected and these extracts showed excellent antioxidant activity presenting dose-dependent relationship. For antibacterial potential, all tested strains are more sensitive to Thymus extracts than Rosmarinus extracts. However, for antifungal activities, only Rosmarinus extracts inhibited mycelial growth. HPLC analysis allowed the identification of ten compounds with the abundance of gallic acid. CONCLUSION: This study showed important bioactivities (antioxidant, antimicrobial, and safety potential) of the plant species RO, TA and TC used in traditional medicine.