Cyrene™ is a green alternative to DMSO as a solvent for antibacterial drug discovery against ESKAPE pathogens

Abstract

Dimethyl sulfoxide (DMSO) is currently employed across the biomedical field, from cryopreservation to in vitro assays, despite the fact that it has been shown to have an assortment of biologically relevant effects. The amphiphilic nature of DMSO along with its relatively low toxicity at dilute concentrations make it a challenging solvent to replace. A possible alternative is Cyrene™ (dihydrolevoglucosenone), an aprotic dipolar solvent that is derived from waste biomass. In addition to being a green solvent, Cyrene™ has comparable solvation properties and is reported to have low toxicity. Herein the abilities of the two solvents to solubilize drug compounds and to act as non-participatory vehicles in drug discovery for antibacterials are compared. It was demonstrate that the results of standardised antimicrobial susceptibility testing do not differ between drugs prepared from either Cyrene™ or DMSO stock. Moreover, in contrast to DMSO, Cyrene™ does not offer protection from ROS mediated killing of bacteria and may therefore be an improvement over DMSO as a vehicle in antimicrobial drug discovery.

Fig. 1. DMSO but not Cyrene™ protects ESKAPE pathogens from stress-induced ROS-mediated programmed cell death. Exponentially growing cultures were treated with 2× MIC ciprofloxacin for 90 min, followed by immediate plating onto LB agar lacking or containing 2% (vol/vol) DMSO or Cyrene™. After incubation at 37 °C overnight, colonies were counted. Shown are the average values from experiments carried out three times. Error bars indicate deviations as standard errors of the mean.