Microbial cyclic β-(1 → 3),(1 → 6)-glucans as potential drug carriers: Interaction studies between cyclic β-glucans isolated from Bradyrhizobium japonicum and betulinic acid

Betulinic acid (BA), a pentacyclic triterpenoid, is a very promising therapeutic drug with varied medicinal properties but it has low water solubility and consequentially low bioavailability. Cyclic β-(1 → 3),(1 → 6)-glucans (CBG), microbial cyclooligosaccharides produced by Bradyrhizobium japonicum ATCC 10324 having a cavity structure and good solubility in water have been tested for their ability to encapsulate betulinic acid and drug-binding interactions of CBG and BA were studied. First, in silico approach was employed to study the scope of any interaction between the CBG and BA. Then, the cyclic glucan-betulinic acid complexes were prepared in three compositions of 1:1, 1:2 and 1:3 CBG:BA. The complexes were analysed using UV-VIS spectroscopy, IR spectroscopy, powder XRD, differential scanning calorimetry (DSC) and thermogravimetric analysis (TGA) to confirm the computational results and consequently the encapsulation efficiency was found to be 9.53%.