Polyphenolic-polysaccharide conjugates from medicinal plants of Rosaceae/Asteraceae family protect human lymphocytes but not myeloid leukemia K562 cells against radiation-induced death.

The aim of the study was to investigate whether the polyphenolic-polysaccharide conjugates (PPCs), isolated from flowers of Sanguisorba officinalis L. and Erigeron canadensis L., and from leaves of Fragaria vesca L. and Rubus plicatus Whe. Et N. E., can protect human peripheral blood mononuclear cells (PBMCs) against gamma-irradiation damage while maintaining the radiosensitivity of the myeloid leukemia K562 cell line. PPCs isolated from the four plant sources are water-soluble macromolecules (14-50 kDa) that were previously chemically and structurally characterized. Cells were incubated with PPCs (25 μg/ml, 1 h) prior exposure to 15 Gy gamma-irradiation, non-irradiated appropriate samples served as controls. It was found that the PPCs were able to increase the post-radiation viability of PBMCs by inhibiting apoptosis, while they did not protect the leukemic cells against radiation-induced apoptotic death. The PPCs offered an efficient protection of PBMCs through scavenging of intracellular ROS and decreasing DNA damage, while they provided no reduction of the oxidative stress and DNA damage in K562 cells. Our findings strongly suggest that the PPCs, especially these isolated from S. officinalis and E. canadensis, can selectively protect normal lymphocytes against radiation injury, therefore they meet the criteria of radioprotectors for potential use in radiotherapy.