Human African trypanosomiasis is a devastating disease with only a few treatment options, including pentamidine. Diamidine compounds such as pentamidine, DB75, and DB820 are potent antitrypanosomal compounds. Previous investigations have shown that diamidines accumulate to high concentrations in trypanosomes. However, the mechanism of action of this class of compounds remains unknown. A long-hypothesized mechanism of action has been binding to DNA and interference with DNA-associated enzymes. The fluorescent diamidines, DB75 and DB820, have been shown to localize not only in the DNA-containing nucleus and kinetoplast of trypanosomes but also to the acidocalcisomes. Here we investigate two series of analogs of DB75 and DB820 with various levels of in vitro antitrypanosomal activity to determine whether any correlation exists between trypanosome accumulation, distribution, and in vitro activity. Despite wide ranges of in vitro antitrypanosomal activity, all of the compounds investigated accumulated to millimolar concentrations in trypanosomes over a period of 8 h. Interestingly, some of the less potent compounds accumulated to concentrations much higher than those of more potent compounds. All of the compounds were localized to the DNA-containing nucleus and/or kinetoplast, and many were also found in the acidocalcisomes. Accumulation in the nucleus and kinetoplast should be important to the mechanism of action of these compounds. The acidocalcisomes may also play a role in the mechanism of action of these compounds. This investigation suggests that the extent of accumulation alone is not responsible for killing trypanosomes and that organelle-specific accumulation may not predict in vitro activity.Diamidine compounds, such as pentamidine, propamidine, and diminazene, have been used for many years as chemotherapeutic agents for infections caused by a variety of microbes, including parasites and fungi. Pentamidine has been used for almost 60 years as a treatment for human African trypanosomiasis and is also used to treat leishmaniasis and the opportunistic infection Pneumocystis pneumonia (32). Diminazene has been used widely for treatment of animal trypanosomiasis (9) and has also been used in humans (25). Recently, pafuramidine, or DB289, a methamidoxime prodrug of the diamidine DB75 (furamidine), has been developed as an oral treatment for early-stage sleeping sickness caused by Trypanosoma brucei gambiense. DB289 is currently in phase III clinical trials in sub-Saharan Africa (6). In addition to DB75 and DB289, a library of diamidines and prodrugs has been synthesized, with various activities against many parasites (1-3, 14-18, 32).Although diamidines have been used therapeutically for over half a century, their mechanism of action is not well understood. Many mechanisms of action have been proposed (32), but one mechanism of action of diamidines that has often been hypothesized is binding to DNA in the nucleus or kinetoplast, leading to interference of DNA-associated enzymes, such as topoisomerase II (27, 34)....

Five O-alkoxyamidine analogues of the prodrug 2,5-bis[4-methoxyamidinophenyl]furan were synthesized and evaluated against Trypanosoma brucei rhodesiense in the STIB900 mouse model by oral administration. The observed in vivo activity of these prodrugs demonstrates that compounds with an O-methoxyamidine or O-ethoxyamidine group effectively cured all trypanosome-infected mice, whereas prodrugs with larger side-chains did not completely cure the mice. Permeability across Caco-2 cell monolayers and microsomal metabolism were used to identify the underlying mechanisms of prodrug efficacy.

Experiments were conducted for the standardization of in vitro culture technique for the mass propagation of Stevia rebaudiana, a medicinally important, zero-calorie value, sweet tasted and an antidiabetic herb. Shoot tip, nodal segment and leaf were used as explants and they were cultured on Murashige and Skoog (MS) medium supplemented with different concentrations of BA, Kn and IAA both in individual and in combined form for shoot inductions and the best results were obtained from MS medium supplemented with BA+ IAA at the concentrations of 1.0 mg/l and 0.5 mg/l respectively. Among the explants used, shoot tip stood first in inducing shoot development. Best root formation of in vitro developed shoots could be achieved on half-strength Nitsch (N 6 ) medium supplemented with IAA at concentration 1.0 mg/l. The in vitro developed plantlets were transferred to pot and they were grown in greenhouse for hardening and finally they were planted in the open filed. Around 82% of plants were successfully established in natural field condition.