Sarothrin from Alkanna orientalis Is an Antimicrobial Agent and Efflux Pump Inhibitor

Abstract

An Alkanna orientalis leaf and flower extract inhibited the growth of Staphylococcus aureus, a pathogen that causes an estimated 478,000 hospitalizations in the US annually. Bioassay-guided fractionation of A. orientalis resulted in isolation of the flavonoid sarothrin (5,7,4′-trihydroxy-3,6,8-trimethoxyflavone), which inhibited the growth of Mycobacterium smegmatis (MIC 75 μM) and S. aureus (MIC >800 μM), and possessed efflux pump inhibitory activity. This is the first report of antimicrobial or efflux pump inhibitory activity of sarothrin, and of its presence in A. orientalis. Our findings suggest that the effectiveness of A. orientalis extracts is due to a combination of multiple constituents, including sarothrin.

Alkanna orientalis (L.) Boiss. plant isolated cultures and antimicrobial activity of their extracts: phenomenon, dependence on different factors and effects on some membrane-associated properties of bacteria

“…Efflux mechanisms like multidrug efflux pumps (MEPs) have become broadly recognized as major components of resistance to many classes of antibiotics (Stavri et al 2007;Gibbons 2008;Bame et al 2013). A novel and promising approach to deal with multidrug resistance is to improve the clinical performance of various antibiotics by employing MEPs inhibitors.…”

“…The absorbance of bacterial suspension was measured after 24 h of incubation at 37°C at the wavelength of 560 nm using the spectrophotometer Genesys 10S UV-Vis (Thermo Scientific, USA). MIC was determined as the lowest concentration of the investigated extract that completely inhibited the growth of the test microorganism (Bame et al 2013). The desired concentration of the test organism suspension was obtained by serial dilutions, as described (Benson 2002).…”

“…This method allows revealing the spectrum of studied material influence (Scorzoni et al 2007;Bame et al 2013). The extracts under investigation (100 lL) were introduced to the wells in the agar with test microorganisms.…”

“…Some biologically active compounds of different plants including Alkanna sp. (Boraginaceae) possess detoxifying properties by means of inactivating the microbe toxins and have antioxidant and cytotoxic effects (Baronetz et al 2001;Oktyabrsky et al 2009;Gharehmatrossian et al 2012;Sykłowska-Baranek et al 2012;Bame et al 2013). Quinones of plant origin are known to have antimicrobial activity among these compounds (Gafner et al 1996;Nagata et al 1998).…”

“…It has been revealed that sarothrin from Alkanna orientalis (L.) Boiss. (Boraginaceae) as an antimicrobial agent can inhibit efflux pumps activity of Staphylococcus aureus (Bame et al 2013).…”