New perspectives of purple starthistle (Centaurea calcitrapa) leaf extracts: phytochemical analysis, cytotoxicity and antimicrobial activity

Ethnobotanical and ethnopharmacological studies of manyCentaureaspecies indicated their potential in folk medicine so far. However, investigations of differentCentaurea calcitrapaL. extracts in terms of cytotoxicity and antimicrobial activity against phytopathogens are generally scarce. The phenolic profile and broad antimicrobial activity (especially towards bacterial phytopathogens) of methanol (MeOH), 70% ethanol (EtOH), ethyl-acetate (EtOAc), 50% acetone (Me2CO) and dichloromethane: methanol (DCM: MeOH, 1: 1) extracts ofC. calcitrapaleaves and their potential toxicity on MRC-5 cell line were investigated for the first time. A total of 55 phenolic compounds were identified: 30 phenolic acids and their derivatives, 25 flavonoid glycosides and aglycones. This is also the first report of the presence of centaureidin, jaceidin, kaempferide, nepetin, flavonoid glycosides, phenolic acids and their esters inC. calcitrapaextracts. The best results were obtained with EtOAc extract with lowest MIC values expressed in mu g/mL ranging from 13 to 25, while methicillin resistantStaphylococcus aureuswas the most susceptible strain. The most susceptible phytopathogens werePseudomonas syringaepv.syringae,Xanthomonas campestrispv.campestrisandAgrobacterium tumefaciens. The highest cytotoxicity was recorded for EtOAc and Me2CO extracts with the lowest relative and absolute IC(50)values between 88 and 102 mu g/mL, while EtOH extract was the least toxic with predicted relative IC(50)value of 1578 mu g/mL. Our results indicate that all tested extracts at concentration considered as non-toxic can be one of great importance in combat towards phytopathogenic and human pathogenic strains, as well as natural sources of antimicrobials.