Stability of Curcumin Improved in Hydrophobic Based Deep Eutectic Solvents

Abstract

Turmeric is a commonly known natural spice that contains many phytoconstituents. Among which Curcumin is a polyphenol present in turmeric responsible for many pharmacological actions. Curcumin is still used as a traditional medicine in fields such as Ayurvedic, Siddha, and Unani. Though Curcumin has a large number of activities, it has disadvantages, such as small shelf life due to poor chemical stability, poor absorption results in less bioavailability, less water solubility, rapid metabolism results in quick elimination from the systemic circulation. A Deep eutectic solvent (DES) is a new class of solvents. Hydrophobic DES can be used for dissolving water-insoluble compounds. DES can be prepared when two solid components mixed in a particular proportion are converted into liquid. DES can be used as a solvent for dissolving water-insoluble compounds and to increase the stability. In this work initially, curcumin linearity studies were conducted in different buffers. A buffer showing maximum absorbance was selected from the linearity studies. Then, DES was prepared by combining Camphor:Menthol (1:1) (CM-DES), Camphor:Thymol (1:1) (CT-DES) and, Menthol:Thymol (1:1) (MT-DES). The stability of curcumin in different DES was determined from the stock and working solutions in benchtop condition (room temperature) and, refrigerator condition (5±3°C). Only working solution stability was determined in the in vitro media temperature (37±2°C). From this study, it was concluded that 50 mM Sodium dihydrogen orthophosphate with 0.5% SLS at pH 5.5 showed maximum absorbance value compared with other buffers, so it was selected for further studies. From stability studies, it was found that curcumin in CM-DES was found to be stable in both stock and working solutions compared to the other two CT-DES and MT-DES.