A TLC-Direct Bioautography Method for Detection of Antiurolithiatic Metabolites

Hyperoxaluria is major urinary disorder troubling largest population throughout the world predominantly involving calcium oxalate (CaOx) crystals. Ancient Ayurvedic system of medicine in India claims better option in treatment of urolithiasis. A plant from "Pashanbheda" group is Phyllanthus niruri L., possessing antiurolithiatic activity, needed to be screened and validated. In the present study, a rapid, easy and efficient method for CaOx crystal inhibition in the agar gel system analogous to antimicrobial well diffusion assay is proposed. A novel thin-layer chromatography (TLC)-direct bioautography method was also proposed to detect the antilithiatic metabolites. It helps to localize the active metabolites in P. niruri, further the partial structure elucidation was characterized by High Resolution Liquid Chromatography by mass spectroscopy (LC-HRMS) analysis. The agar well diffusion method shows 50% inhibitory concentration (IC50) value at 228.55 and 493.529 mg/mL for tri-sodium citrate and P. niruri extract, respectively. The lowest concentration showing visible crystal inhibition (minimum inhibitory concentration, MIC) in both samples was found to be 20 mg/mL. In this study, a unique agar gel well diffusion and TLC-direct bioautography method successfully screened, detected and confirmed CaOx crystal inhibitory metabolites from P. niruri. The tuberonic acid was detected in bioactive fraction of P. niruri by LC-HRMS characterization.