Two immunosuppressive compounds from the mushroom Rubinoboletus ballouii using human peripheral blood mononuclear cells by bioactivity-guided fractionation

Rubinoboletus ballouii is an edible mushroom wildly grown in Yunnan province, China. Up till now, little was known about the chemical and biological properties of this mushroom. The aim of this study was to investigate the immunomodulatory effects of the ethanolic extract of Rubinoboletus ballouii and its fractions on human peripheral blood mononuclear cells (PBMCs) using bioactivity-guided fractionation. The crude extract of the fruiting bodies of RB was fractionated by high-speed counter current chromatography (HSCCC). Twelve fractions were obtained and the third fraction (Fraction C) exerted the most potent anti-inflammatory activities in mitogen-activated PBMCs. Further fractionation of fraction C led to the isolation of two single compounds which were elucidated as 1-ribofuranosyl-s-triazin-2(1H)-one and pistillarin, respectively. The results showed that both 1-ribofuranosyl-s-triazin-2(1H)-one and pistillarin exhibited significant immunosuppressive effects on phytohemagglutinin (PHA)-stimulated human PBMCs by inhibiting [methyl- ³H]-thymidine uptake and inflammatory cytokines productions such as tumor necrosis factor (TNF)-α, interleukin (IL)-10, interferon (IFN)-γ and IL-1β. Besides, 1-ribofuranosyl-s-triazin-2(1H)-one was firstly found in natural resources, and pistillarin was also isolated from the family Boletaceae for the first time. They exhibited great potential in developing as anti-inflammatory reagents.