In vitro and in vivo antiviral properties of sulfated galactomannans against yellow fever virus (BeH111 strain) and dengue 1 virus (Hawaii strain)

Two galactomannans, one extracted from seeds of Mimosa scabrella, having a mannose to galactose ratio of 1.1, and another with a 1.4 ratio from seeds of Leucaena leucocephala, were sulfated. The products from M. scabrella (BRS) and L. leucocephala (LLS) had a degree of sulfation of 0.62 and 0.50, and an average molecular weight of 620×10 3 and 574×10 3 g mol −1, respectively. Their activities against yellow fever virus (YFV; BeH111 strain) and dengue 1 virus (DEN-1; Hawaii strain) were evaluated. This was carried out in young mice following intraperitoneal infection with YFV. At a dose of 49 mg kg −1, BRS and LLS gave protection against death in 87.7 and 96.5% of the mice, respectively. When challenged with 37.5 LD50 of YFV, mice previously inoculated with BRS+virus or LLS+virus, showed 93.3 and 100% resistance, respectively, with neutralization titers similar to mice injected with 25 LD50 of formaldehyde-inactivated YFV. In vitro experiments with YFV and DEN-1 in C6/36 cell culture assays in 24-well microplates showed that concentrations that produced a 100-fold decrease in virus titer of YFV were 586 and 385 mg l −1 for BRS and LLS, respectively. For DEN-1 they were 347 and 37 mg l −1, respectively. Sulfated galactomannans, thus demonstrate in vitro and in vivo activity against flaviviruses.