Abstract

Phaeogyroporus portentosus is widely consumed as food in Thailand, but its potential bioactivities remain largely unknown. Here, the bioactivities of the hot water-extractable polysaccharide-protein complex (PPC) were evaluated after precipitating with ethanol. This crude PPC extract was then fractionated by DEAE-cellulose ion exchange column chromatography, and subsequently further purified by Superdex G-200 gel filtration column chromatography, giving an abundant polysaccharide fraction (PPC-P11) and a much less common fraction (PPC-P12) that was obtained in an insufficient amount for further analysis. The PPC-P11 fraction was characterized for its molecular weight and its functional groups were determined by ¹³C and ¹H NMR spectroscopy, FT-IR spectroscopy and gel permeation chromatography (GPC) respectively. It contained a high amount of glucose with an average molecular weight of 294.7 kDa (as compared to < 21.5 kDa by reducing SDS-PAGE analysis). The NMR signal observed at 103.5 ppm was assigned to the C1 of beta-glucose, and those between 20 and 40 ppm suggest the presence of a glucan-protein compound. PPC-P11 was found to display a dose-dependent antioxidant capacity in each of the four complementary test systems assayed (hydrogen peroxide, DPPH, ABTS and nitric oxide free radical scavenging) with quite low IC₅₀ values (< 100 µg/mL). Moreover, a relatively strong in vitro antiproliferative effect was found against five human cell lines, with IC₅₀ values ranging from 1.178 ± 0.129 µg/mL (breast cancer; BT474) to 5.183 ± 0.229 µg/mL (hepatoma cancer; HEP-G2). PPC-P11 from P. portentosus is, therefore, a potential antioxidant source for both health medicines and the food industry.

Key words: Antioxidation, antiproliferation, polysaccharide-protein complex,Phaeogyroporus portentosus