Prenylated polyphenolic compounds from Glycyrrhiza iconica and their antimicrobial and antioxidant activities

Abstract A new prenylated isoflavan, iconisoflavan (1), and a new prenylated isoflav-3-ene, iconisoflaven (2) were isolated from the roots of Glycyrrhiza iconica together with four known ones namely (3S)-licoricidin (3), licorisoflavan A (4), topazolin (5) and glycycoumarin (6). The structures were elucidated on the basis of extensive spectroscopic analysis including 1D and 2D NMR as well as HR-MS. Furthermore, the absolute configurations of compounds 1, 3 and 4 were established by electronic circular dichroism (ECD). All the isolated compounds (1-6) were evaluated for their in vitro antimicrobial activities against five pathogenic bacteria and one yeast (Candida albicans) using an in vitro microdilution method. Compounds 1 and 3-5 displayed significant activity against Salmonella typhimurium ATCC 13311 with MIC values ranging from 2 to 8 μg/mL. Additionally, all compounds were screened for their in vitro free radical scavenging activities using an in vitro microdilution DPPH assay spectrofotometrically. The tested compounds exhibited IC<inf>50</inf> values in the range of 0.18-0.56 mg/mL, suggesting an activity comparable with that of ascorbic acid (IC<inf>50</inf>: 0.07 mg/mL). To the best of our knowledge, the present study constitutes the first phytochemical and bioactivity investigation on G. iconica.