The concept of NADES as vehicles in drug delivery is quite new.
Curcumin was selected as a model compound to challenge the solubilizing
and stabilizing properties of such excipients and to gain further
understanding of their physicochemical properties. In a recent paper
we have demonstrated the solubilizing effect of NADES on a porphyrin
photosensitizer (THPP) as well as the ability to potentiate the in vitro
bacterial phototoxic effect of that PS (Wikene et al., 2015). The current
work further emphasizes the suitability of NADES as a hydrophilic
solvent for compounds with low aqueous solubility, but it also demonstrates
that the composition of the eutectic solvent must be optimized
for the individual solute.
There was apparently no direct relation between the solubilizing
potential of the NADES with respect to curcumin and the polarity,
water content or pH. The five NADES with the most promising features
towards curcumin solubilization appeared more polar than water,
contained up to 45% water, yet solubilized curcumin in the 10−4 M
range. For comparison, the solubility of curcumin in aqueous solution
(pH b 6) is ≤ 3 × 10−8 M (Tønnesen et al., 2002; Esmaili et al., 2011).