Methods for using proanthocyanidin polymers having antiviral activity

A method of treating a respiratory virus infection, comprising administering to a warm-blooded animal an effective amount of an antiviral agent comprising a proanthocyanidin polymer which polymer is obtained from a Croton species and is characterized by:

• (a) the capability of dissolving in water and/or an aqueous solution;
• (b) the capability of exerting a pronounced antiviral effect when administered in vivo to an animal or a human;
• (c) having a structure comprising flavonoid units selected from the group consisting of catechins, epicathechins, gallocatechins, galloepicatechins and combinations thereof;
• and
• (d) .sup.13 C NMR spectra having peak position at .delta.154.2, 145.1, 143.7, 132.8, 131.2, 130.3, 120.9-118.6 (series of broad peaks), 116.1, 115.4, 114.3, 108.0, 106.3, 96.6, 95.3, 81.8, 77.6, 75.3, 72.6, 71.5, 65.6, 37.1, 35.3, and 27.7.

A method for treating a respiratory syncytial virus infection, comprising administering, to a warm-blooded animal, an effective amount of an antiviral agent comprising a proanthocyanidin polymer wherein said proanthocyanidin polymer is obtained from a Croton tree by a method which comprises:

• (a) extracting the whole plant, the bark, the stems, the roots or the latex of the Croton tree with a lower alcohol of about 1-3 carbons, acetone, water or other water miscible solvent or combinations thereof to obtain an aqueous soluble fraction;
• (b) subjecting the aqueous soluble fraction to gel filtration using water and/or water and a water miscible solvent with or without a buffer as the mobile phase;
• or to reversed-phase column chromatography using water, and/or water and a water miscible solvent as the mobile-phase;
• or to gel permeation chromatography using water and/or water and water miscible solvent and acetonitrile with or without a buffer as the mobile phase, or combination thereof;
• and
• (c) collecting the fractions detectable by ultraviolet spectroscopy having a .lambda. maximum at about 200-350 nm,
• wherein the collected fraction is characterized by:
• (i) the capability of dissolving in water and/or an aqueous solution;
• (ii) the capability of exerting a pronounced antiviral effect when administered in vivo to an animal or a human;
• (iii) having a structure comprising flavonoid units selected from the group consisting of catechins, epicathechins, gallocatechins, galloepicatechins and combinations thereof;
• and
• (iv) .sup.13 C NMR spectra having peak position at .delta.154.2, 145.1, 143.7, 132.8, 131.2, 130.3, 120.9-118.6 (series of broad peaks), 116.1, 115.4, 114.3, 108.0, 106.3, 96.6, 95.3, 81.8, 77.6, 75.3, 72.6, 71.5, 65.6, 37.1, 35.3, and 27.7.