Anthraquinone profile, antioxidant and antimicrobial properties of Frangula rupestris (Scop.) Schur and Frangula alnus Mill. bark

Frangula rupestris and Frangula alnus are deciduous shrubs distributed in Balkan Peninsula. While the bark of F. alnus is medicinally widely used, little is known about chemical and biological properties of F. rupestris. In the present study, F. rupestris and F. alnus bark were evaluated for their reducing power, DPPH radical scavenging and chelating activity, as well as antioxidant activity in β-carotene-linoleic acid assay. In addition, phenolic content, anthraquinone profile and antimicrobial activity of F. rupestris and F. alnus bark were determined. The most represented anthraquinone derivatives in F. rupestris and F. alnus bark were physcion (0.11 mg/g) and emodin (2.03 mg/g), respectively. Both species demonstrated excellent antioxidant and antimicrobial activities with MIC values equal or lower than 2.5 mg/mL. The presented research indicates that both species may have health benefits as natural antioxidants and antimicrobial agents for use in functional foods or medicine.