Triazoxins: Novel nucleosides with anti-Giardia activity

Novel nucleoside analogues named “triazoxins” were synthesized. Of these, two analogues were found to be highly effective against Giardia lamblia, an intestinal parasite and a major cause of waterborne infection, worldwide. While compound 7 reduced the growth of trophozoites in culture (IC₅₀, ~5 μM), compound 21 blocked the in vitro cyst production (IC₅₀ ~5 μM). Compound 21 was also effective against trophozoites (IC₅₀, ~36 μM). A third analogue (compound 8) was effective against both trophozoites (IC₅₀, ~36 μM) and cysts (IC₅₀, ~20 μM) although at higher concentration. Thus triazoxin analogues are unique and exhibit morphology (i.e., trohozoites or cysts) -specific effects against Giardia.