Conversion of 6-protoilludene into illudin-M and -S by

The role of bracken fern illudanes in bracken fern-induced toxicities

Bracken fern is carcinogenic when fed to domestic and laboratory animals inducing bladder and ileal tumours and is currently classified as a possible human carcinogen by IARC. The carcinogenic illudane, ptaquiloside (PTQ) was isolated from bracken fern and is widely assumed to be the major bracken carcinogen. However, several other structurally similar illudanes are found in bracken fern, in some cases at higher levels than PTQ and so may contribute to the overall toxicity and carcinogenicity of bracken fern. In this review, we critically evaluate the role of illudanes in bracken fern induced toxicity and carcinogenicity, the mechanistic basis of these effects including the role of DNA damage, and the potential for human exposure in order to highlight deficiencies in the current literature. Critical gaps remain in our understanding of bracken fern induced carcinogenesis, a better understanding of these processes is essential to establish whether bracken fern is also a human carcinogen.

Draft genome of Omphalotus olearius provides a predictive framework for sesquiterpenoid natural product biosynthesis in Basidiomycota

The secondary metabolome of Basidiomycota represents a largely uncharacterized source of pharmaceutically relevant natural products. Terpenoids are the primary class of bioactive compounds isolated from mushrooms. The Jack O'Lantern mushroom Omphalotus olearius was identified 50 years ago as a prolific producer of anticancer illudin sesquiterpenoids; however, to date there have been exceptionally few studies into the biosynthesis of these important compounds. Here, we report the draft genome sequence of O. olearius, which reveals a diverse network of sesquiterpene synthases and two metabolic gene clusters associated with illudin biosynthesis. Characterization of the sesquiterpene synthases enabled a comprehensive survey of all currently available Basidiomycota genomes, thereby creating a predictive resource for terpenoid natural product biosynthesis in these organisms. Our results will facilitate discovery and biosynthetic production of unique pharmaceutically relevant bioactive compounds from Basidiomycota.

Sesquiterpenes of Lactarius and Russula (Mushrooms): An Update[1]

In this review the biogenesis, structures, and bioactivities of all sesquiterpenoids isolated from Russula and Lactarius species in the last decade are critically discussed, and divided into sections according to their skeletons. A brief chemotaxonomic overview of the family Russulaceae is reported in the final part of the review.

Novel illudins from Coprinopsis episcopalis (syn. Coprinus episcopalis), and the distribution of illudin-like compounds among filamentous fungi

The illudins are a family of fungal sesquiterpenes that have been studied as anti-tumor agents, and they also have antibacterial activity. Over a four-year period, 25 304 fungal isolates (approximately 97% ascomycetes and 3% basidiomycetes), were screened for antibacterial activity against methicillin-resistant Staphylococcus aureus. Illudin-like compounds with antibacterial and cytotoxic activity against tumor cell lines were observed in 10 basidiomycete strains. The isolates were recovered from different types of substrata using indirect methods and only formed sterile mycelia in pure culture. The isolates were genetically related but not identical, based on PCR-based fingerprinting techniques. DNA sequencing of the ITS1-5.8 S-ITS2 region of the strains revealed that nine had identical sequences, indicating that they were conspecific. The sequence of the remaining isolate was 96.34% similar, suggesting that it was a closely related species. The D1-D2 region of the 25 S rRNA gene of the two strain types was also sequenced. Both sequences were 99.39% similar, and Coprinopsis gonophylla (syn. Coprinus gonophyllus) was the closest match for both. Strains were grown in pure culture on a rice-based medium that allowed the development of basidiomata from one culture of the main strain type, which was identified as C. episcopalis, a close relative of C. gonophyllus. Both species (or strain types) produced different types of illudin-like compounds. Three novel illudins (I, I2 and J2) were found to be produced by the cultures identified as C. episcopalis, while only illudinic acid was produced by the other Coprinopsis sp. The taxonomical relationships of the Coprinops is species identified in this study with other illudin producers previously reported in the literature are discussed.

New plant growth promoters, repraesentins A, B and C, from Lactarius repraesentaneus

Three new plant growth regulatory sesquiterpenoids were isolated from the Lactarius repraesentaneus fungus. Their structures were elucidated to be a protoilludene sesquiterpene, namely repraesentin A (1), and two related sesquiterpenes, namely repraesentins B (2) and C (3). Compounds 1-3 showed promotion activities toward the radicle elongation of lettuce seedlings by 136%, 118% and 184% at 67 ppm, respectively.

Mutagenicity of ptaquiloside, the carcinogen in bracken, and its related illudane-type sesquiterpenes. I. Mutagenicity in Salmonella typhimurium

Ptaquiloside, a potent carcinogen of an illudane-type sesquiterpene glycoside isolated from Pteridium aquilinum, and its related compounds, hypolosides having the same nucleus isolated from the Pteridaceae, exhibited marked mutagenicity in the modified Ames test with Salmonella typhimurium TA98 and TA100 using a preincubation at pH 8.5. Illudins M and S, sesquiterpenes of the same illudane type from basidiomycetes, also exhibited mutagenicity. The structural requirements for mutagenicity are discussed.

Mutagenicity of ptaquiloside, the carcinogen in bracken, and its related illudane-type sesquiterpenes. II. Chromosomal aberration tests with cultured mammalian cells

The chromosomal aberration test using a Chinese hamster lung cell line (CHL) was carried out on ptaquiloside and its related compounds, hypoloside B, hypoloside C, illudin M and illudin S. Ptaquiloside induced chromosomal aberrations at doses as low as 4.5 micrograms/ml (0.0113 mM). The clastogenic effect was pH-dependent. The same activity was observed at a 90-fold higher dose at pH 5.3 in the culture medium compared with the activity at pH 7.4 or pH 8.0. Both hypoloside B and hypoloside C were also clastogenic at almost the same dose level as that of ptaquiloside. Illudin M and illudin S were also potent clastogens and induced aberrations at much lower doses than ptaquiloside. These results suggest that the clastogenic effect is involved in the mechanism of carcinogenic potency of ptaquiloside in animals.