Anticancer activity of the Uncaria tomentosa (Willd.) DC. preparations with different oxindole alkaloid composition

The activity of Uncaria tomentosa preparations on cancer cells was studied using in vitro and in vivo models. IC50 values were calculated for preparations with different quantitative and qualitative oxindole alkaloid composition: B/W37 – bark extracted in water at 37 °C, B/Wb – bark extracted in boiling water, B/50E37 – bark extracted in 50% ethanol at 37 °C, B/Eb – bark extracted in boiling 96% ethanol, B/96E37 – bark extracted in 96% ethanol at 37 °C and B/SRT – bark extracted in water and dichloromethane. Generally, the results obtained showed a high correlation between the total oxindole alkaloid content (from 0.43% to 50.40% d.m.) and the antiproliferative activity of the preparations (IC50 from >1000 μg/ml to 23.57 μg/ml). B/96E37 and B/SRT were the most cytotoxic preparations, whereas the lowest toxicity was observed for B/W37. B/96E37 were shown to be active against Lewis lung carcinoma (LL/2) [IC50 = 25.06 μg/ml], cervical carcinoma (KB) [IC50 = 35.69 μg/ml] and colon adenocarcinoma (SW707) [IC50 = 49.06 μg/ml]. B/SRT was especially effective in inhibiting proliferation of cervical carcinoma (KB) [IC50 = 23.57 μg/ml], breast carcinoma (MCF-7) [IC50 = 29.86 μg/ml] and lung carcinoma (A-549) [IC50 = 40.03 μg/ml]. Further animal studies on mice bearing Lewis lung carcinoma showed significant inhibition of tumor growth by B/W37 administered for 21 days at daily doses of 5 and 0.5 mg (p = 0.0009). There were no significant changes in the cell cycles of tumor cells with the exception of cell decrease at the G2/M phase after the administration of B/96E37 at a daily dose of 0.5 mg and the G1/G0 cells cycle arrest demonstrated after the B/SRT therapy at a daily-dose of 0.05 mg. All tested preparations were non-toxic and well tolerated.