The present study was carried out to better understand the importance of comfrey, Symphytum officinale L., as a medicinal plant which has been used to differents humans deseases, through an extensive bibliographic review about fitochemistry and terapeutical point of view. In this review, emphasis is given to the pyrrolizidine alkaloids for its ambigous activities whether carcinogenics or as a anti-tumor agents. After that, were proposed the study of the variation of total alkaloids contents in comfrey leaves produced from two differents soils type influence: Litosol type and Latosol type respectively situated in Tiete and Campinas, both cities of São Paulo State. Gravimetric and titulometric methods were used to quantify total alkaloidal contents. Its was performed a thin layer chromatography, to obtain the separation of alkaloids from the inicial mixture, and to permit a qualitative and a semi-quantitative comparative valuation the two original datas. The gravimetric analysis did not appoint differences between the two soils with respect their influences under alkaloidal contents in comfrey leaves. But, by titulometric methods was possible to establish differences between means originated from each soils data. In this sense, latossolic soil datas showed the lower content in confront with the litosol type, the last reaching twice total alkaloids contents. Through thin layer chromatography was possible to identify the following alkaloids from the crude base mixture: 7-acetyl-lycopsamine + 7-acetyl-intermedine, lycopsamine + intermedine and echimidine.