Preparation and anti-HIV activity of low-molecular-weight carrageenans and their sulfated derivatives

Abstract

Lambda-, kappa-, and iota-carrageenan were depolymerized in the presence of ferrous ions or ferrous ions plus ascorbic acid at room temperature. Tetrabutyl-ammonium salts of lambda-, kappa- and iota-carrageenan were dissolved in N,N-dimethylformamide and sulfated by the addition of pyridine-sulfur trioxide in N,N-dimethylformamide. Then, the sulfated carrageenans were depolymerized by the incubation with ferrous ions and ascorbic acid. The anti-HIV activities of the various preparations were determined in a system in which MT-4 cells were infected with HTLV-IIIB. The activity of lambda-carrageenan was similar to that of dextran sulfate and the depolymerized lambda-carrageenan retained high activity. The activities of kappa- and iota-carrageenan and their depolymerized forms were about 6% of that of lambda-carrageenan. The sulfation of kappa-and iota-carrageenan increased the activities of these compounds to the same level as that of lambda-carrageenan. However, the sulfation of lambda-carrageenan did not affect its activity. Depolymerized sulfated kappa- and iota-carrageenan with mean molecular weights of 50,000 (81,000-46,000) had higher anti-HIV activity than dextran sulfate and all other preparations of carrageenan tested.