Olive leaf extract (OLE), prepared from the fresh or dried leaves of Olea europaea L., is generating interest as a cardiovascular and metabolic disease risk modifier. Positive effects for the leaf extract and its key phytochemical constituents have been reported on blood pressure, respiratory infections, inflammation, and insulin resistance. A variety of OLE products are available both over-the-counter and for professional dispensing. The aim of this research was to quantitatively explore the phytochemical profile of different OLE products on the Australian market. Ten OLE products available on the Australian market (five over-the-counter products and five products for professional compounding and dispensing) were quantitatively analyzed for oleuropein, hydroxytyrosol, oleacein, oleocanthal, total biophenols, maslinic acid, and oleanolic acid, using high-performance liquid chromatography (HPLC). Substantial variation in oleuropein and hydroxytyrosol levels was noted between extracts, with a trend towards higher oleuropein and lower hydroxytyrosol levels being noted in products produced using the fresh olive leaf as opposed to dry olive leaf. These results suggest that OLE products on the Australian market vary substantially in their phytochemical profiles. Products for professional compounding and dispensing in many cases contained less oleuropein than over-the-counter products, but more hydroxytyrosol and comparable total biophenol levels.
Keywords: OLE; Olea europaea; herbal medicine; hydroxytyrosol; oleuropein; olive leaf; olive leaf extract; phytoequivalence; phytomedicine.