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Heparin is an important polyanionic drug having a wide variety of different biological activities. Substantial research effort has focused on the preparation of improved heparins and heparin analogues that might exhibit higher specificity and decreased side effects. These heparin analogues or heparinoids include sulfated polysaccharides from plant and animal origin, synthetic derivatives of polysaccharides, and acidic oligosaccharides and their small synthetic analogues. The structure, biological activities and therapeutic potential of these heparinoids are discussed.

Mangostin, the major xanthone of Garcinia mangostana, and a series of synthetic derivatives were investigated for their in vitro antiplasmodial activity against Plasmodium falciparum. Mangostin itself showed moderate activity, but prenylated xanthones containing alkylamino functional groups exhibited quite potent antiplasmodial activity. Some structure-activity relationships are proposed.

The dichloromethane extract of the tuberous roots of Viguiera aspillioides was tested in vitro against T. cruzi and then investigated in order to identify its active compounds, which were the known diterpenes (-)-ent-kaur-16-en-19-oic acid, (-)-trachyloban-19-oic acid, and (-)-kauran-16alpha-ol. Synthetic derivatives of the acidic compounds were obtained and tested; one of them, (-)-kaur-16-en-19-ol, was also active. Their IC50 are given.

Five new sesquiterpenoids, three monocyclofarnesane, and two cuparane derivatives, isolated from the liverwort Ricciocarpos natans (L.) Corda have been tested against Biomphalaria glabrata, one of the snail vectors of schistosomiasis (bilharzia). Molluscicidal activity is exhibited by four of the sesquiterpenoids with an LC100 of 11 ppm of the most toxic compound. Lunularic acid, a common growth inhibitor of liverworts, and five of its synthetic derivatives have also been tested, and two derivatives were found to be highly active.