New perspectives of purple starthistle (Centaurea calcitrapa) leaf extracts: phytochemical analysis, cytotoxicity and antimicrobial activity
Authors: Dimkic, Ivica; Petrovic, Marija; Gavrilovic, Milan; Gasic, Uros; Ristivojevic, Petar; Stankovic, Slavisa; Janackovic, Peda
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.
Minutes-delayed Jets from a Neutron Star Companion in Core-collapse Supernovae
Authors: Soker, Noam
This paper presents cases in which a neutron star (NS; or a black hole) companion to a type-Ib or type-Ic (stripped-envelope) core-collapse supernova (CCSN) accretes mass from the explosion ejecta and launches jets minutes to hours after explosion. The NS orbits at a pre-explosion radius of a similar or equal to 1-5 R-circle dot. When the ejecta velocity drops to v(ej) less than or similar to 1000-1500 km s(-1), the ejecta gas that the NS accretes possesses sufficient specific angular momentum to form an accretion disk around the NS. The NS accretes a fraction of (M-acc,M- d/M-ej) approximate to 3 x 10(-5)-3 x 10(-4) of the ejecta mass through an accretion disk over a time period of t(jets) approximate to 10 minutes-few hr. If the jets carry about 10% of the accretion energy, then their total energy is a fraction of about 0.003-0.03 of the kinetic energy of the ejecta. The implications of these jets from an NS (or a black hole) companion to a CCSN are the shaping of the inner ejecta to have a bipolar morphology, energizing the light curve of the CCSN, and in some cases the possible enrichment of the inner ejecta with r-process elements.