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

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.