Evaluation of cytotoxic and antioxidant activity of Rhaponticum carthamoides (Willd.) Iljin extracts

Rhaponticum carthamoides (Willjd) Iljin is a Siberian plant used for centuries in the folk medicine. Its extracts possess immunomodulating activity and may stimulate the protein synthesis in muscles and kidneys. Their activity is mainly attributed to ecdysteroids – steroid compounds occurring in plants and in insects. This study was focused on antioxidant and cytotoxic activity of R. carthamoides extracts.

Plant material (dry leaves) was obtained from FITOSTAR™. Secondary metabolites were extracted via sonication (30min.), using three solvents, differning in polarity: chloroform, methanol and water.

Radical scavenging activity (RSA) of the extracts was measured in the DPPH (2,2-diphenyl-1-pichydrazyl free radical) assay and was compared with the activity of known antioxidants: ascorbic acid, α-tocopherol and butylated hydroxytoluene (BHT). Aqueous and methanolic extracts exhibited radical scavenging activity towards DPPH (IC₅₀=25 and 45µg/mL, respectively) and turned to be more effective than BHT (IC₅₀=190µg/mL), but less than ascorbic acid and alpha-tocopherol (IC₅₀=4 and 12µg/mL, respectively). In the same time chloroformic extract was not capable of scavenging DPPH (IC₅₀ >1mg/mL).

Cytotoxic activity of all three extracts and pure 20-hydroxyecdysone (20E) was examined against HeLa (cervical carcinoma) and HL-60 (leukemia) cell lines, using MTT assay. Aqueous extract as well as pure 20E did not influence the cell lines viability, whereas chloroformic and methanolic extracts exhibited mild cytotoxic activity. However according to the NCI recommendation (IC₅₀ <4µg/mL) neither of them can be regarded as a potential cytotoxic agent.

Acknowledgements: State Committee for Scientific Research Nr PBZ-KBN-092/P05/2003