Antibacterial metabolites from Australian macrofungi from the genus Cortinarius

Cortinarius species were evaluated for anti- Pseudomonas and anti- Staphylococcus activity. Chemical constituents of Cortinarius basirubescens, including the isomers of austrocortilutein, were identified and showed antibacterial activity. In this study, ethyl acetate and aqueous fractions from 117 collections of Australian macrofungi belonging to the mushroom genus Cortinarius were screened for antimicrobial activity against Staphylococcus aureus and Pseudomonas aeruginosa. Overall, the lipophilic fractions were more active than the aqueous fractions. The ethyl acetate fractions of most or all collections of 13 species, namely Cortinarius ardesiacus, C. archeri, C. austrosaginus, C. austrovenetus, C. austroviolaceus, C. coelopus, C. [ Dermocybe canaria] 2 Denotes a species belonging in Cortinarius, but which has not been formally transferred to that genus. 2 , C. clelandii, C. [ D. kula], C. memoria-annae, C. persplendidus, C. sinapicolor, C. vinosipes and forty seven collections of un-described Cortinarius species exhibited IC 50 values of ⩽0.09 mg/mL against S. aureus. In contrast, most or all collections of only four species, namely C. abnormis, C. austroalbidus, C. [ D. kula], C. persplendidus, and eleven un-described Cortinarius collections exhibited similar effects against P. aeruginosa (IC 50 ⩽ 0.09 mg/mL). Anthraquinonoid pigments isolated from C. basirubescens together with emodin physcion and erythrogluacin were assessed for their antimicrobial activity. The fungal octaketides austrocortilutein, austrocortirubin, torosachrysone, physcion and emodin were found to strongly inhibit the growth of S. aureus (IC 50 0.7–12 μg/mL) whereas only physcion and emodin exhibited potency against P. aeruginosa (IC 50 1.5 and 2.0 μg/mL, respectively).