An unusual 2-O-glyceryl-glycosyl--pyrone from Erigeron annuus (L.) with potential antifungal activity: in-vitro and in-silico study

Phytochemical characterisation of the polar fraction of Erigeron annuus extract led to the isolation of glycerylerigeroside (1), a unique gamma-pyrone derivative. Structure of 1 was decided by intensive study of NMR and mass spectra as 3-O-[4'-((1,3-dihydroxypropan-2-yl)oxy)-beta-D-glucopyranoside)]-4H-pyran-4-one, with uncommon glyceroxy side chain attached to 4' position of pyromeconic acid beta-D-glucopyranoside. Antimicrobial potential of 1 was tested against Staphylococcus aureus, Salmonella enterica, and Candida albicans. Compound 1 strongly inhibited growth of Candida albicans (MIC = 17.24 mu M/disc), compared to fluconazole (MIC = 16.33 mu M/disc). Meanwhile, it moderately inhibited the growth of Staphylococcus aureus (MIC = 71.84 mu M/disc) and Salmonella enterica (MIC = 71.84 mu M/disc), as compared with thiophenicol (MIC = 14.05 mu M/disc) and (MIC = 14.05 mu M/disc), respectively. The binding mode of 1 with the active site of sterol 14 alpha-demethylase (CYP51) from Candida albicans (PDB ID: 5TZ1), in combination with fluconazole, was predicted by molecular docking study and supported the antifungal activity.