Identification of Throuba Thassos, a traditional Greek table olive variety, as a nutritional rich source of oleuropein.

The content of polyphenols in table olives is highly influenced by the olive variety and the debittering process applied on the fruits. Nine commercial types of Greek table olives were examined for their content in oleuropein and hydroxytyrosol. A very simple extraction procedure and a chromatographic methodology were applied for the simultaneous quantitation of oleuropein (OE) and hydroxytyrosol (HT) in drupes, using boiling water extraction followed by direct HPLC analysis. Hydroxytyrosol was found in all the types of olives that were studied. Kalamata olives and Green "tsakistes" of the variety Megaritiki contained the highest quantity of hydroxytyrosol (1.8-2.0 mg/fruit) followed by Greek-style "chondrolies" with quantity 1.0 mg/fruit. Oleuropein was found in small quantities in two cases, but in the case of Throuba Thassos which is processed by dry salt in a traditional Greek way, oleuropein was found in important quantities (1.2 mg/fruit) recorded over a 4-year period. This is the most important finding of this study showing that this particular table olive type is a nutritional rich source of oleuropein. Additionally, assuming a usual consumption of 20 olive fruits per day, an approximate quantity of 25 mg of oleuropein per day can be considered as safe for human use, since it can be found in the usual diet.