CYTOTOXIC AND ANTI-PROLIFERATIVE EFFECTS OF RHODODENDRON PONTICUM L. EXTRACT ON RAT GLIOMA CELL LINE (F98)

The genus Rhododendron has been widely used in traditional medicine. Rhododendron ponticum L. (R. ponticum) contains grayanotoxins with diterpene qualities. The aim of this study was to investigate in vitro cytotoxic and antiproliferative effects of R. ponticum L. extract on glioma in a rat glioma cell line (F98) and to calculate the amounts of grayanotoxins I and III. Rhododendrons were gathered from the Eastern Black Sea region of Turkey during the common flowering period. Their flowers were dried under suitable conditions, extracted with distilled water and lyophilized. The amounts of grayanotoxin I and III in the common rhododendron extract were determined by the chromatographic method. The cytotoxic and antiproliferative activities of different concentrations of the R. ponticum L. extract in mitochondrial (MTT) and lysosomal (Neutral red) assays was evaluated in glioma F98 cell lines. It was determined that the R. ponticum L. extract with a grayanotoxin I amount of 55.75 μg/kg and a grayanotoxin III amount of 7.4 μg/kg had a dose-dependent cytotoxic effect. IC₅₀ was found to be 122.8 µg/ml in the MTT and 79.61µg/ml in the neutral red (NR) assay. Previous studies show that R. ponticum L. may prevent high proliferative activity of tumor cells by its cytotoxic effects. The predictable amounts of grayanotoxin I and/or III may be preferred as a natural remedy for treatment of incurable glioma, which is one of the most common brain tumors in humans.