Chemical investigation of Paxillus involutus (Batsch) Fr. led to the isolation of a pair of new enantiomers (E)-5-(4-methoxy-2-oxo-2H-pyran-6-yl)pent-4-en-1-yl 2-hydroxypropanoate (1a/1b) along with 14 known compounds (2-15) for the first time from this mushroom. The structures of new compounds were elucidated based on extensive spectroscopic data analysis of MS, 1D and 2D NMR, and their absolute configurations were confirmed by comparison of the experimental and calculated ECD data. Compounds 1a and 1b exhibited radical scavenging activities with IC50 values ranging from 10.39 ± 2.26 to 20.43 ± 3.74 μg/mL. Compounds 1a and 1b also showed moderate anti-tyrosinase activity with IC50 value of 25.66 ± 2.84 and 26.82 ± 3.19 μg/mL.
Keywords: Paxillus involutus; anti-tyrosinase activity; antioxidant activity; α-pyrone.