In vitro anti-HIV-1 activity of fucoidan from Sargassum swartzii

•FF2 fraction showed 95.6% inhibition in the HIV-1 P24 assay.•The activilty was comparable to the positive control.•Fractions were found to be non toxic upto 1000μg/ml. Sargassum swartzii, a marine brown algae with wide range of biological properties belongs to the family Sargassaceae. Bioactive fucoidan fractions (CFF, FF1 and FF2) were isolated from S. swartzii and characterized by linear gradient anion-exchange chromatography and FT-IR. The characterized fucoidan fractions contained mainly sugars, sulfate and uronic acid. In the present study, anti-HIV-1 property of the fucoidan fractions was investigated. Fraction FF2 was found to exhibit significant anti-HIV-1 activity at concentrations of 1.56 and 6.25μg/ml as observed by >50% reduction in HIV-1 p24 antigen levels and reverse transcriptase activity. Fucoidan fractions have no cytotoxic effects on PBMCs at the concentration range of 1.56–1000μg/ml. These results suggest that fucoidan fractions could have inhibitory activity against HIV and has potential as an anti-HIV-1 agent.