Is it possible to block the fusion of the E protein of dengue virus with heparin receptors by using natural products like extract of basil leaf or papaya etc?
In theory, it is possible providing there are molecules that binds heparin receptor in the compounds that you are testing for. However, other factors should also be considered, for example, the concentrations, amount, half-life etc. of the molecules or binding with or without the presence of dengue viral particles.
One needs to consider the effects on human cells when heparin receptor is blocked as these receptors are also functions in cellular responses such as Wnt/wingless pathways, some cytokine pathways (IL8, IFNg etc). And they also involve in cell proliferation and thus have a very wide cellular function in vivo.