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Eight previously undescribed sesquiterpenoids, tremutins A−H (1−8), together with three known ones (9−11), were isolated from cultures of the basidiomycetes Irpex lacteus. Structures of the new compounds together with absolute configurations were elucidated on the basis of extensive spectroscopic methods, as well as single-crystal X-ray diffractions and equivalent circulating density calculations. Compounds 1 and 2 possess an unusual 6/7-fused ring system that might be derived from a tremulane framework. Compounds 3−7 and 9−11 are tremulane sesquiterpenoids of which 4 and 5 are the first tremulane examples with a 1,2epoxy moiety to be reported. Compounds 6, 7, 10, and 11 possess weak activities to several human cancer cell lines. Compound 8 shows a weak inhibitory effect on NO production with a half maximal inhibitory concentration (IC 50 ) value of 22.7 μM. Compound 1 inhibits the lipopolysaccharide (LPS)-induced proliferation of B lymphocyte cells with an IC 50 value of 22.4 μM, while 2 inhibits concanavalin A (Con A)-induced T cell proliferation and LPS-induced B lymphocyte cell proliferation with IC 50 values of 16.7 and 13.6 μM, respectively.

Guanacastane diterpenoids with an unusual 5/7/6 tricyclic skeleton mainly produced by basidiomycete fungi represent a structurally intriguing class of natural products. While the chemical synthesis of several members has been achieved, the biochemical and genetic basis of their biosynthesis remain unknown. Herein, we present the identification and characterization of two crucial enzymes in the biosynthesis of guanacastane diterpenoids in Psathyrella candolleana. Heterologous expression reveals that PsaD, a typical class I diterpene synthase, catalyzes the cyclization of geranylgeranyl diphosphate to form a new guanacastane-type diterpene, guanacasta-1,3-diene (7). Moreover, we demonstrate that PsaA, a cytochrome P450 monooxygenase, can catalyze multiple oxidations of 7 to yield guanacastepene U (8). These results provide new opportunities for genome mining and metabolic engineering of guanacastane diterpenoids.

To comprehensively understand the chemical constituents of the edible mushroom Agrocybe salicacola and their biological functions, a phytochemical separation of the cultural broth of A. salicacola led to the isolation of four new illudane sesquiterpenoids, agrocybins H–K ( 1 – 4 ), along with 10 known analogues ( 5 – 14 ). Compounds 2 – 4 were racemates of which 2 and 3 were further separated into single enantiomers as 2a / 2b and 3a / 3b . All new structures with absolute configurations were elucidated on the basis of an extensive spectroscopic analysis and quantum chemistry calculations. Compound 1 possesses a new carbon skeleton that might be derived from the protoilludane backbone. Compounds 1 , 5 , 8 , and 9 show a certain degree of cytotoxicity to five human cancer cell lines. Compound 1 shows a mild inhibitory effect on nitric oxide production with an IC 50 value of 31.4 μM. It is concluded that A. salicacola is rich in illudin derivatives with potential bioactivity prospects, which would make A. salicacola a good material of medicine and food homology.

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