Solubilization of phytocomplex using natural deep eutectic solvents: A case study of Ginkgo biloba leaves extract

Botanical natural bioactive ingredients are difficult to purify due to their complicated composition and structure, and are usually utilized in the form of phytocomplex, which refers to a mixture of multiple bioactive ingredients. Using biocompatible solvents as delivery solvents is a simple, versatile, and scalable method to improve the solubility of phytocomplex. In this work, the extract of Ginkgo biloba leaves (EGb) was chosen as the model of the phytocomplex to systematically investigate the potential of natural deep eutectic solvents (NADESs) as solubilizers. After initial screening, the solubilities of EGb in different NADESs were 29–1500 folds higher than those in water. Several solvatochromic parameters of NADESs were employed to tentatively study the solvation between bioactive compounds and NADESs. The high solubility of EGb in NADESs could be interpreted by the hydrogen bond interactions. Additionally, further investigation on the stability and bioactivity of EGb dissolved in NADESs helped to validate the feasibility of using NADESs as solubilizers. The results suggested that not only the stability but also the bioactivity of EGb kept at high levels after dissolving in NADESs. The findings of this study showed the bright application prospect of NADESs as solubilizers, which offers a new avenue for improving the solubility of insoluble phytocomplex.