Sardinian plants with antimicrobial potential. Biological screening with multivariate data treatment of thirty-six extracts.

• Cytinus hypocistis has a broad spectrum antibacterial activity. • Limonium morisianum has potent anti-staphylococcal properties. • P. terebinthus ssp. terebinthus inhibits multi-drug resistant K. pneumoniae strains. • Total phenolic content has a positive relationship with antibacterial activity. In this paper, thirty-six extracts from Sardinian plants were evaluated in vitro for their antimicrobial activity towards a panel of reference strains, Staphylococcus aureus , S. epidermidis , Klebsiella pneumoniae and Escherichia coli , and for their cytotoxicity on mammalian cells. The biological data, together with total phenolic and flavonoid content of the extracts, were treated by PCA (Principal Components Analysis), which highlighted the positive correlation among total phenolic content and increasing antibacterial activities, and a possible involvement of flavonoids in mitigate the cytotoxicity. Thirteen extracts displayed relevant IC 50 values (half maximal inhibitory concentration) on S. aureus (IC 50 from 1.4 to 153.6 μg/mL), ten out of them were active also against S. epidermidis (IC 50 from 3.9 to 150 μg/mL), seven against K. pneumoniae (IC 50 from 28.5 to 97.5 μg/mL), and two against E. coli (IC 50 74.9 and 156.3 μg/mL). In particular, three extracts obtained from Pistacia terebinthus ssp. terebinthus, Cytinus hypocistis and Limonium morisianum emerged as promising antibacterial candidates. They exhibited remarkable inhibitory activity towards bacterial strains from clinical specimens and presenting different antibiotic-resistance profiles. [ABSTRACT FROM AUTHOR]