Methods for preparing viral neuraminidase inhibitors including antiviral peptides by specifically chemically modifying disulfide bonds in precursor molecules. A method of inhibiting viral neuraminidases by administering a viral neuraminidase inhibitor comprising an antiviral peptide prepared by the above methods and inhibiting the viral neuraminidase. Therapeutics for inhibiting viral neuraminidases, including effective amounts of viral neuraminidase inhibitors including antiviral peptides derived from selectively chemically modified disulfide bonds in precursor molecules, and present in a pharmaceutically acceptable carriers.