Exploiting olive leaves for herbal preparations rich in bioactive radical scavengers
Olive leaf (OLL) exploitation as a source of bioactive ingredients is currently gaining interest among scientists from various fields and the industry. Some of the traditional therapeutic uses of OLL extracts are now attributed to the health positive effects of phenolic constituents present . As any other natural source, leaf is subjected to the influence of a number of factors, such as cultivar, environment, agronomic practices and sampling . Such factors may notably affect the composition and antioxidant potential of the final raw plant material that it is used further on for the preparation of standardized formulations. In this view the study of the variability of OLL bioactive composition and antioxidant potency is of emerging importance, taking into account that industry is interested in product standardization in terms of content and/or potency of constituents present, which should be easily and inexpensively ensured.
Different types of OLLs were selected on the same day from one olive tree. Various methods were then applied to assess variability in the polar extracts regarding radical scavenging potential, total phenol content and phytochemical profile. HPLC coupled in series with diode array and fluorimetric detectors as well as LC-MS were used to highlight qualitative and quantitative variations in individual phenolic ingredients. The findings indicated a qualitative unwavering phenolic profile, with quantitative differentiations in individual phenolics that did not influence the total radical scavenging potential of extracts. The findings were strengthen by studies on the effect of cultivar and sampling date factor on the antioxidant potential of leaf extracts with regard to phenolic content/HPLC profile. Useful observations and suggestions are made for the establishment of OLL as a potent natural source of bioactive ingredients suitable for commercialization, irrespective of cultivar, sampling period or leaf type.
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