Monolein Aqueous Dispersions as a Tool to Increase Flavonoid Solubility: A Preliminary Study

Topical application of flavonoids has recently received increased attention, however their use is limited due to a low aqueous solubility and related low in vivo absorption. Monolein emulsified in water leads to aqueous nanostructured dispersions of complex lyotropic liquid crystalline phases able to carry lipophilic molecules. These monoolein aqueous dispersions (MADs) were investigated on two model flavonoids, namely quercetin and rutin. MADs were produced by emulsifying monoolein in water in the presence of sodium cholate. MAD size, morphology and drug content were characterized using PCS, SdFFF, cryo-TEM and UV spectroscopy. In vitro studies on drug release and antioxidant activity were also conducted. MAD size was found around 300 nm. CryoTEM showed that sodium cholate content influences the morphological aspect of MAD. Concerning drug content, MAD increased at least 80-fold quercetin solubility, while the same was not found for rutin. Experiments on antioxidant activity demonstrated the two-fold power of quercetin as compared to rutin while in vitro Franz cell experiments showed that MAD are suitable for cutaneous application. In conclusion MAD can be potentially proposed for the delivery of the antioxidant molecule quercetin, whilst many studies have to be performed for finding a way to deliver rutin.