Three Mediterranean species from natural plant communities (Ceratonia siliqua, Pistacia lentiscus, and Olea europaea var. sylvestris): phenolic acids, flavonoids, and biological activities

This study focuses on the phytochemical analysis of the leaves of three Mediterranean species from natural community native to Tunisia. A separated and a mixed leaves extracts were prepared using three species (Ceratonia siliqua L. (C), Pistacia lentiscus L. (L) and Olea europaea L. var. sylvestris or oleaster (O)). Four leaves hydroethanolic extracts including C, L, O and mixed extract coded MCLO (1/3, 1/3, 1/3) were used. The total polyphenols, flavonoids and condensed tannins were determined by colorimetric method. The identification of phenolic profile was performed HPLC-DAD/MS analysis. The antioxidant activity was evaluated by two tests and the antimicrobial activity was done against some clinical microbial pathogens. Results showed that the mixture MCLO extract gave the highest free radical-scavenging activity (IC50 = 0.057 g/mL) and showed an amount of 35.347 mg GAE /g DM of total polyphenols content. As well, the MCLO exhibited significant antibacterial and antifungal activities against the tested pathogen strains except of Candida albicans. Likewise, the MCLO possesses lysozyme activity against Staphylococcus aureus (282.66 AU/mL/min) and showed the highest percentage of inhibition on biofilm formation (97.28%). A total of 14, 11 and 8 phenolic compounds were identified in C, L and O extracts, respectively. Though, in the mixture MCLO extract, 21 phenolic compounds were identified. The high biological activities found with the mixture extract could be related to the three distinguished phenolics acids; trigalloyl-glc (261.10 µg/mL), trigalloylquinic acid (254.68 µg/mL), and digalloyl-glc (225.21 µg/mL). These finding highlights the improvement of the biological activities of carob, lentisk and oleaster using mixed leaves extracts.