Polyphenols and secoiridoids in raw material (Olea europaea L. leaves) and commercial food supplements

Twenty-five compounds, among which flavonoids and secoiridoids, were separated and quantified after extraction from Olea europaea leaves. Differences were found in total polyphenols content and in oleuropein depending on cultivar, production area, sampling time (pruning or harvest time), and state of leaves (fresh, refrigerated, dried, frozen, or lyophilized). Polyphenols content in fresh leaves ranged from 34.21 to 7.87 mg/g, while oleuropein content changes from 21.03 to 2.79 mg/g in fresh leaves of different cultivars and decreases after the drying process. The differences are discussed in order to exploit these by-products for food supplements. In addition, five commercial food supplements from olive leaves were analyzed, and their total polyphenol, secoiridoids, and flavonoid contents were detected by HPLC/DAD analysis. In order to provide stable contents of bioactive molecules, all the above-mentioned variabilities should be taken into account.