Neogrifolin

Neglected tropical diseases affect the world's poorest populations with soil-transmitted helminthiasis and schistosomiasis being among the most prevalent ones. Mass drug administration is currently the most important control measure, but the use of the few available drugs is giving rise to increased resistance of the parasites to the drugs. Different approaches are needed to come up with new therapeutic agents against these helminths. Fungi are a source of secondary metabolites, but most fungi remain largely uninvestigated as anthelmintics. In this report, the anthelmintic activity of Albatrellus confluens against Caenorhabditis elegans was investigated using bio-assay guided isolation. Grifolin (1) and neogrifolin (2) were identified as responsible for the anthelmintic activity. Derivatives 4-6 were synthesized to investigate the effect of varying the prenyl chain length on anthelmintic activity. The isolated compounds 1 and 2 and synthetic derivatives 4-6, as well as their educts 7-10, were tested against Schistosoma mansoni (adult and newly transformed schistosomula), Strongyloides ratti, Heligmosomoides polygyrus, Necator americanus, and Ancylostoma ceylanicum. Prenyl-2-orcinol (4) and geranylgeranyl-2-orcinol (6) showed promising activity against newly transformed schistosomula. The compounds 1, 2, 4, 5, and 6 were also screened for antiproliferative or cytotoxic activity against two human cancer lines, viz. prostate adenocarcinoma cells (PC-3) and colorectal adenocarcinoma cells (HT-29). Compound 6 was determined to be the most effective against both cell lines with IC50 values of 16.1 µM in PC-3 prostate cells and 33.7 µM in HT-29 colorectal cells.

Neogrifolin, a natural biologically active substance isolated from the edible bodies of the mushroom Albatrellus confluens, has been shown to possess several pharmacological properties. No studies were investigated against osteosarcoma cancer. Hence, in this study, we investigated the apoptosis-inducing effects and the mechanisms of neogrifolin on human osteosarcoma cells. Our results demonstrated that neogrifolin induced concentration- and time-dependent suppression of proliferation. Further, induction of apoptosis in U2OS and MG63 osteosarcoma cell lines were also observed. Neogrifolin induced the release of cytochrome c accompanied by activation of caspase-9, caspase-3 and cleavage of poly (ADP-ribose) polymerase (PARP). In addition, z-VAD-fmk, a universal inhibitor of caspases, prevented caspase-3 activation and PARP cleavage and inhibited neogrifolin-induced cell growth inhibition. Furthermore, neogrifolin treatment resulted in a reduction of phosphorylated AKT level, FOXO transcription factor, and glycogen synthase kinase 3 (GSK3). Knockdown of GSK3 with siRNA inhibited the apoptotic effects of neogrifolin. On the other hand, neogrifolin treatment also down-regulated the expression of the inhibitor of apoptosis protein (IAP) in both osteosarcoma cells. Collectively, our results suggested that neogrifolin is a potential candidate for osteosarcoma.

In our search for bioactive mushrooms native to British Columbia, we determined that the ethanol extracts from fruiting bodies of the terrestrial polypore Albatrellus flettii had potent anti-cell viability activity. Using bioassay-guided fractionation, mass spectrometry and nuclear magnetic resonance, we successfully isolated three known compounds (grifolin, neogrifolin and confluentin). These compounds represent the major anti-cell viability components from the ethanol extracts of A. flettii. We also identified a novel biological activity for these compounds, specifically in down-regulating KRAS expression in two human colon cancer cell lines. Relatively little is known about the anti-cell viability activity and mechanism of action of confluentin. For the first time, we show the ability of confluentin to induce apoptosis and arrest the cell cycle at the G2/M phase in SW480 human colon cancer cells. The oncogenic insulin-like growth factor 2 mRNA-binding protein 1 (IMP1) has been previously shown to regulate KRAS mRNA expression in colon cancer cells, possibly through its ability to bind to the KRAS transcript. Using a fluorescence polarization assay, we show that confluentin dose-dependently inhibits the physical interaction between KRAS RNA and full-length IMP1. The inhibition also occurs with truncated IMP1 containing the KH1 to KH4 domain (KH1to4 IMP1), but not with the di-domain KH3 and KH4 (KH3&4 IMP1). In addition, unlike the control antibiotic neomycin, grifolin, neogrifolin and confluentin do not bind to KRAS RNA. These results suggest that confluentin inhibits IMP1-KRAS RNA interaction by binding to the KH1&2 di-domains of IMP1. Since the molecular interaction between IMP1 and its target RNAs is a pre-requisite for the oncogenic function of IMP1, confluentin should be further explored as a potential inhibitor of IMP1 in vivo.