Olive leaf phenolic extract from two Portuguese cultivars –bioactivities for potential food and cosmetic application

Abstract Olea europaea L. is historically one of the most important trees of the Mediterranean countries. A second-order polynomial models were used to optimize the recovery of polyphenols from olive leaves from two typically produced Portuguese cultivars ‘Negrinha do Freixo’ and ‘Cornicabra’. The model obtained produced a satisfactory fit for both cultivars for total polyphenols, total flavonoids, and antioxidant activity. At the best conditions (6 h, 50% ethanol and 1:20 w-v), extracts with a higher level of phenolics were obtained for the cultivar ‘Negrinha do Freixo’ (40.14 ± 4.35 mg GAE g-1 dry leaves) followed by ‘Cornicabra’ (27.10 ± 1.29 mg GAE g-1 dry leaves). The predominant phenolic acids were oleuropein derivatives accounting for a total amount of 58.81 and 23.49 mg g-1 dry leaf followed by oleosides with 45.16 and 32.09 mg g-1 dry leaf in ‘Negrinha’ and ‘Cornicabra’ respectively. Extracts had a strong potential as an antiaging ingredient and cosmetic/food preservative exhibiting antioxidant activity, capacity to inhibit elastase (82.5% and 87.5%), collagenase (98.7% and 50%) and tyrosinase (50% and 33%) for ‘Negrinha do Freixo’ and ‘Cornicabra’, respectively at a concentration of 5 mg mL-1. The ‘Negrinha do Freixo’ had the highest potential as an antimicrobial agent at 50 mg mL-1 being the minimum inhibitory concentration for E. coli, S. enterica and S. aureus and exhibited an inhibition of 70% and 67% for P. aeruginosa and B. cereus, respectively.