Phenolic compounds and in vitro immunomodulatory properties of three Andalusian olive leaf extracts

Phenolic compounds in extracts of three olive leaf cultivars were determined using HPLC-DAD-TOF-MS. The determination of the immunomodulatory properties of the whole phenolic extracts was then carried out on RAW 264 mouse macrophages as a preliminary in vitro study. Twenty-eight phenolic compounds were determined in the olive leaf extracts and high contents of total phenolics were shown, particularly for 'Picual' cultivar. In addition, all olive leaf extracts inhibited the release of the pro-inflammatory mediator nitric oxide in LPS-stimulated RAW264.7 cells revealing their immunomodulatory properties. As a preliminary result, it could be deduced that the inhibition of NO by the olive leaf extract may depend on the type of phenolic compounds rather than on the total phenolic contents. This is the first time that whole phenolic extracts of olive leaves have been used in in vitro study of their anti-inflammatory properties.