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Three sesquiterpene lactones (centaurepensin = chlorohyssopifolin A, chlorojanerin and 13-acetyl solstitialin A) isolated from the aerial parts of Centaurea solstitialis L. ssp. solstitialis (Asteraceae) were investigated for antimicrobial and antiviral activities. For the antimicrobial activity assessment, both standard and isolated strains of Escherichia coli, Pseudomonas aeruginosa, Enterococcus faecalis, Staphylococcus aureus, Candida albicans and C. parapsilosis were employed by the microdilution method. Herpes simplex type-1, a DNA virus, and Parainfluenza, an RNA virus, were employed for the determination of the antiviral activity of these three sesquiterpene lactones using Vero cell lines. Ampicilline, ofloxocine, ketoconazole, fluconazole, acyclovir and oseltamivir were used as the reference drugs. 13-Acetyl solstitialin A displayed remarkable antibacterial activity against isolated strains of E. faecalis at 1 microg/ml concentration, which was close to the effective concentrations of ampicillin. The same compound also showed significant activity against the DNA virus, being as potent as the reference compound acyclovir at maximum and minimum concentrations of 16-<0.00006 microg/ml. This is the first report showing that 13-acetyl solstitialin A possesses significant antiviral activity.

The guaianolide type sesquiterpene lactones chlorojanerin, 13-acetyl solstitialin A and solstitialin A were identified as the anti-ulcerogenic components of the chloroform extract of the aerial parts of Centaurea solstitialis ssp. solstitialis (Asteraceae). In this study, these compounds were investigated by using various in vivo ulcer models in rats and mice. Chlorojanerin was shown to be significantly effective in preventing the induction of lesions by ethanol- (EtOH-) (both oral and subcutaneous administration), indomethacin-, indomethacin plus HCl/EtOH-, N(G)-nitro-l-arginine methyl ester plus EtOH-, N-ethylmaleimide plus EtOH-, water immersion and restraint stress, and serotonin, as well as inhibiting titratable gastric acidity and acid output, and increasing gastric pH, but was ineffective in the prevention of ulcers induced by pyloric ligation, diethyldithiocarbamate, and cysteamine, and had no effect on gastric secretion volume or peptic activity. A mixture of 13-acetyl solstitialin A (95%) and solstitialin A (5%) was found to be significantly effective against EtOH-induced lesions on oral administration but was ineffective when administered subcutaneously. This mixture was also found to be effective in preventing lesions induced by EtOH, indomethacin, indomethacin plus HCl/EtOH, N(G)-nitro-l-arginine methyl ester plus EtOH, N-ethylmaleimide plus EtOH, water immersion and restraint stress, serotonin and cysteamine, as well as inhibiting titratable gastric acidity and titratable acid output, and gastric pH, but was found ineffective against the pyloric ligation-induced and diethyldithiocarbamate-induced ulcerogenesis models, as well as gastric secretion volume and peptic activity. On the other hand, active compounds did not show any toxic effect on acute toxicity (3 days administration) evaluation tests in mice.

The fresh spiny flowers of Centaurea solstitialis ssp. solstitialis (CSS) are used for the treatment of peptic ulcers in Turkey. Ethanol (80%) extract of CSS exhibited significant anti-ulcerogenic effect on the ethanol-induced ulcerogenesis model in rats. The ethanol extract was further fractionated by successive solvent extractions with n-hexane, chloroform, ethyl acetate and n-butanol. All fractions showed significant anti-ulcerogenic activity, however, the effect of the chloroform fraction was found to be more prominent with 99.5% ulcer inhibition. Bioassay-guided fractionation yielded sesquiterpene lactones as the active components. The main components responsible for the activity of the chloroform fraction were determined as chlorojanerin and 13-acetyl solstitialin A which were elucidated by HR-ESI and (1)H, (13)C and 2D NMR spectroscopic techniques.