Three new polyacetylene glycosides (PAGs) from the aerial part of Launaea capitata (Asteraceae) with anti-biofilm activity against Staphylococcus aureus

Abstract

Four polyacetylenic glycosides, three of which are new, together with two known flavonoids were isolated from the methanol extract of the aerial parts of Launaea capitate, designated bidensyneoside A1 (1), 6´–O-acetyl-bidensyneoside A1 (2), bidensyneoside E (3), bidensyneoside F (4), luteolin (5) and luteolin-7-glucoside (6) also known as cynaroside. Their structures were elucidated by comprehensive analysis of 1D, 2D-NMR and HR-MS data. The absolute configuration of the bidensyneosides was determined by Mosher ester analysis and the optical rotation values. The isolated compounds were tested against biofilm formation of Staphylococcus aureus as well as against several pathogens including Gram-positive bacteria, Gram-negative bacteria, fungi and yeasts. Furthermore, they were tested for their cytotoxicity against two cancer cell lines L929 and KB-3-1. Compound 4 showed moderate inhibition of S. aureus biofilm formation with 30% and 25% at 256 and 128 μg/mL, respectively, while compounds 1 and 5 showed weak inhibition with 20% at 256 μg/mL. Compound 5 showed moderate cytotoxicity against both cell lines L929 and KB-3-1, with IC50 values of 18 μg/mL.