Screening of promising chemotherapeutic candidates from plants against human adult T-cell leukemia/lymphoma (III).

Adult T-cell leukemia/lymphoma (ATL) is a malignancy of mature peripheral T lymphocytes caused by human T-cell lymphotropic virus type I (HTLV-I). In our previous paper, 214 extracts from 162 plants were screened to elucidate the anti-proliferative principles against HTLV-I-infected T-cell lines. In this study, 245 extracts from 182 plants belonging to 61 families were further tested against two HTLV-I-infected T-cell lines (MT-1 and MT-2). Potent anti-proliferative effects were exhibited against MT-1 and MT-2 cells by 52 and 60 of the 245 extracts tested, respectively. Of these, two extracts showed strong inhibitory activity (EC50 values 0.1-1 µg/mL; +++) against both cells, 7 extracts showed moderate inhibitory activity (EC550 values 1-10 µg/mL; ++), and 43 extracts showed weak inhibitory activity (EC50 values 10-100 µg/mL; +), whereas the remaining extracts did not show any activity (EC50 values >100 µg/mL; -) against MT-1 cells. On the other hand, 10 extracts showed moderate inhibitory activit and, 48 extracts showed weak inhibitory activity, whereas the remaining extracts did not show any activity against MT-2 cells. Extracts from the aerial parts of Annona reticulata and A. squamosa showed the most potent inhibitory activity and three aporphine alkaloids were isolated from their extracts as the active principles by activity-guided fractionation.

Screening of promising chemotherapeutic candidates from plants against human adult T-cell leukemia/lymphoma (II): apoptosis of antiproliferactive principle (24,25-dihydrowithanolide D) against ATL cell lines and structure-activity relationships with withanolides isolated from solanaceous plants.

Adult T-cell leukemia/lymphoma (ATL) is an incurable peripheral T-cell malignancy caused by human T-cell lymphotropic virus type I. In our preceding paper, 214 extracts from 162 plants were screened to elucidate the antiproliferative principles against ATL cell lines. Several withanolides were isolated and the structure-activity relationships (SAR) examined. To extend the search for SAR, 31 further withanolides, previously isolated from solanaceous plants, were tested against ATL cell lines. The presence of a 4ß-hydroxy group as well as a 5ß,6ß-epoxy group appeared to be essential for the activity. In contrast, the presence of a sugar moiety at either the 3- or the 27-position led to a reduction in the activity. Furthermore, 24,25-dihydrowithanolide D (13) was identified as the most potent inhibitor, showing selective toxicity against ATL cell lines by inducing apoptotic cell death.