Nanonization of ethanolic tulsi leaf extract and its major compound eugenol and evaluation of their inhibitory potential against calcium oxalate crystal (a kidney stone component)

Abstract The aim of this study was a) to synthesize nanoforms of the whole leaf extract of the flowering herb ‘Tulsi— Ocimum sanctum ’ (regarded as the ‘queen of herbs’ having diverse healing and health-improving properties) and its major constituent eugenol, b) to characterize some of their physico-chemical properties and c) to explore their inhibitory role on formation and disintegration of the kidney stone-former calcium oxalate crystals, through in vitro investigation. Colloidal suspensions of Tulsi-leaf-extract nanoparticles (TLE-NPs) and eugenol nanoparticles (ENPs) were synthesized separately by ultrasonication method through emulsification of hydrophobic TLE/eugenol into hydrophilic protein gelatin. Due to nanonization, water-insoluble TLE/eugenol became water-soluble and thus bioavailable. The average size of the particles was about 35nm for TLE-NPs and 25 nm for ENPs, entrapment efficiency of TLE and eugenol within gelatin was about 20 and 80% respectively, and the release rate of TLE/eugenol from gelatin cap was slow and sustained throughout 72 h for TLE-NPs and 120 h for ENPs. When spectroscopic and microscopic studies were performed on the formation and disintegration of calcium oxalate crystals in presence of TLE-NP and ENP, both types of particles depicted significant inhibitory potential on crystal formation and disintegrating potential on pre-formed crystals, compared to the same doses of their bulk forms i.e., bare TLE and eugenol; ENP was more potent than TLE-NP with respect to crystallization inhibitory activity, whereas they were comparable in crystal disintegration potency. Future in vivo pharmacological and toxicological studies will surely lead to the development of the TLE-NPs and ENPs as potential therapeutic agents against calcium oxalate pathogenesis.