Bioprospecting Davidson's plum and quandong: Cytoprotective and proapoptotic activities

Polyphenolic-rich extracts of commercially grown Davidson's plum (Davidsonia pruriens, Cunoniaceae) and quandong (Santalum acuminatum, A.D.C., Santalaceae) were evaluated for their potential cytoprotective and proapoptotic activities. Quandong extract (0.2-0.6 mg/mL) exhibited superior cytoprotective activities and reduced the hydrogen peroxide (H2O2) induced death of hepatocellular carcinoma (HepG2) cells between 25 and 50%. Davidson's plum extract had comparable antiproliferative activity to blueberries against the colon adenocarcinoma (HT-29) and HepG2 cells but was not effective against the stomach adenocarcinoma cells (AGS; IC50 > 2.0 mg/mL). No significant cytotoxicity was observed towards non-transformed colon (CCD-18Co; IC50 > 2.0 mg/mL) and mixed stomach and intestine (Hs 738.St/Int; IC50 > 2.0 mg/mL) cells. The flow cytometry analysis conducted with promyelocytic leukaemia (HL-60) cells and the results of the cytokinesis blocked micronucleus cytome (CBMNCyt) assay conducted with HT-29 cells suggested an increase in apoptosis in the cellular population treated with the fruit extracts. The occurrence of apoptotic cells coincided with an increase in caspase-3 enzyme activity. The results of the CBMNCyt assay suggested DNA damage in HT-29 cells as a result of treatment with fruit extracts, applied at final concentrations of 0.5 and 1.0 mg/mL.