Illudane Sesquiterpenoids from Edible Mushroom Agrocybe salicacola and Their Bioactivities

Abstract

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 IC₅₀ 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.

Chart 1. Structures of 1–14 Isolated from A. salicacola

Figure 1

Key 2D NMR correlations for 1.

Figure 2

ECD calculations for 1.

Scheme 1. Proposed Biosynthesis Pathway for 1

Figure 3

ECD calculations for 2.

Figure 4

ECD calculations for 3.