An investigation of the anti-oxidant and differentiating activity of polyphenol extracts from olive leaf extracts

Abstract

Acute Myeloid Leukaemia is characterised by an accumulation of myeloid progenitor cells in the bone marrow, where novel therapies are continuously sought especially for older patients as cure rates are low in this cohort. The main aims of this study were to analyse the polyphenol content in olive leaf extracts from two olive tree varieties and investigate their leukaemia differentiating activity on the HL-60 cell line. Phenolics were successfully extracted from olive leaves between September and November 2020 and January 2021 using a methanol-water mixture and a range between 1.93 to 2.75 g olive leaf extracts were obtained per 10 g of starting material. Assessment of flavonoid, phenols and ortho di-phenols, showed a marked increase in November for phenols and ortho di-phenols in both Bidni and Carolea derived extracts, where it is suggested that this increase may serve as protection from fruit fly infestations. When compared to the positive controls Phorbol-12-myristate-13-acetate (10 nM, 100 nM) and 1.6 % Dimethylsulfoxide no evidence of differentiating activity was induced on HL60 cells by the olive leaf extracts from both tree varieties. However, the phenol standard Diosmetin showed strong differentiating activity at 100 ppm (p<0.001) and less so at 25 ppm (p<0.05) compared to PMA 10 nM at day 3. At day 5 apoptosis was induced indicating a loss of leukaemia cell immortality. Further studies are recommended on the phenolic standard Diosmetin.