Macromolecules isolated from Phellinus pini fruiting body: Chemical characterization and antiviral activity

Two major polymers, EP-AV1 and EP-AV2, were purified from the hot-water extract of the Porodaedalea pini (Brot.) Murrill (syn. Phellinus pini) fruiting body by 75% ethanol precipitation and size-exclusion chromatography. These polymers were shown to be polysaccharides consisting of glucose as the main sugar residue as well as other minor sugars, such as galactose, xylose and mannose, and are variants of β-1,3-glucans, with high molecular masses, 1,006 and 100 kDa, respectively. Fourier-transform infrared and elemental analysis suggested that these polymers contained certain level (∼10% in dry mass) of phenolic compounds. Both polymers inhibited plaque formation in Vero cells caused by herpes simplex virus 1 (HSV-1) by 91% and 93% at 5 g/mL, and by the coxsackie virus B3 (CVB3) in HeLa cells by 32% and 84% at 1 mg/mL, respectively. On the other hand, their cytotoxicity to both cells was negligible. Their selectivity indices (ratio CC₅₀/EC₅₀) against the HSV-1 virus were quite high, >25,000 (EP-AV1) and >16,670 (EP-AV2), respectively. These polysaccharides also inhibited the neuraminidase activity in a dose-dependent manner but only at relatively higher concentrations. These results suggest that these water-soluble polysaccharides are promising agents for the treatment of HSV-1 infections.