The activity of Uncaria tomentosa preparations on cancer cells was studied using in vitro and in vivo models. IC (50) values were calculated for preparations with different quantitative and qualitative oxindole alkaloid composition: B/W(37) --bark extracted in water at 37 °C, B/W(b)--bark extracted in boiling water, B/50E(37) --bark extracted in 50% ethanol at 37 °C, B/E(b)--bark extracted in boiling 96% ethanol, B/96E(37) --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 (IC(50) from >1000 μg/ml to 23.57 μg/ml). B/96E(37) and B/SRT were the most cytotoxic preparations, whereas the lowest toxicity was observed for B/W(37). B/96E(37) were shown to be active against Lewis lung carcinoma (LL/2) [IC(50) =25.06 μg/ml], cervical carcinoma (KB) [IC(50) =35.69 μg/ml] and colon adenocarcinoma (SW707) [IC(50) =49.06 μg/ml]. B/SRT was especially effective in inhibiting proliferation of cervical carcinoma (KB) [IC(50) =23.57 μg/ml], breast carcinoma (MCF-7) [IC(50) =29.86 μg/ml] and lung carcinoma (A-549) [IC(50) =40.03 μg/ml]. Further animal studies on mice bearing Lewis lung carcinoma showed significant inhibition of tumor growth by B/W(37) 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/96E(37) at a daily dose of 0.5 mg and the G(1)/G(0) 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.
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