Current trends toward naturally occurring compounds of therapeutic interest have contributed to an increasing number of studies on olive oil phenolics in the treatment of diseases with oxidative and inflammatory origins. Recent focus has been on olive oil wastewater, which is richer in phenolic compounds than olive oil itself. In this review, we present findings demonstrating the potential use of olive mill wastewater in dermatology. Particular attention is given to compounds with proven benefits in topical pharmacology: caffeic and ferulic acids, tyrosol and hydroxytyrosol, verbascoside, and oleuropein. The review is divided into different sections: inflammatory skin diseases, microbial effects, wound healing in addition to the antimelanoma properties of olive mill waste phenolics, and their potential in sun protection agents. There is strong evidence to support further studies into the valorization of this abundant and sustainable source of phenolic compounds for use in dermatology and dermo-cosmetic preparations.

Olive leaves are an abundant but under-exploited by-product of the olive oil industry, comprising 10 % of the total mass processed for olive oil. They are a rich source of oleuropein, the most abundant polyphenol in olive leaves, whose bioactive properties are widely documented. If olive leaves are to be seriously considered as a readily-available source of oleuropein, simple analytical methods are needed to identify varieties and growing conditions conducive to its formation. HPLC-fluorescence detection and UPLC-UV-MS methods on different instruments were developed and cross-validated using blank (oleuropein-free) leaves produced in-house to establish matrix standards in the concentration range 0.4 to 4.8 mg/g. For the HPLC-FLD method, mean repeatability and intermediate precision were respectively 3.64% and 4.76% relative standard deviation; the coefficient of determination was generally >0.9999 and linearity was demonstrated by the Fischer test. There was a close linear relationship (R2 > 0.999) between back-calculated concentrations of both spiked placebos and authentic standards. Analysis of the same spiked placebos by the three chromatographic methods showed no significant differences in the validation results as confirmed by ANOVA. Cross-validation of the three methods indicate that selective quantification can equally be carried out on standard HPLC equipment available to most laboratories or by more sophisticated UPLC-MS techniques in larger structures. The determination of oleuropein in “Olivière” olive variety is reported here for the first time, and leaves collected in 2022 contained about 40 mg/g oleuropein, almost twice the amount found in Picholine and three times more than in other varieties.