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

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 IC50 values (half maximal inhibitory concentration) on S. aureus (IC50 from 1.4 to 153.6 μg/mL), ten out of them were active also against S. epidermidis (IC50 from 3.9 to 150 μg/mL), seven against K. pneumoniae (IC50 from 28.5 to 97.5 μg/mL), and two against E. coli (IC50 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.