Quick identification of xanthine oxidase inhibitor and antioxidant from Erycibe obtusifolia by a drug discovery platform composed of multiple mass spectrometric platforms and thin-layer chromatography bioautography.

As a final step of the purine metabolism process, xanthine oxidase catalyzes the oxidation of hypoxanthine and xanthine into uric acid. Our research has demonstrated that Erycibe obtusifolia has xanthine oxidase inhibitory properties. The purpose of this paper is to describe a new strategy based on a combination of multiple mass spectrometric platforms and thin-layer chromatography bioautography for effectively screening the xanthine oxidase inhibitory and antioxidant properties of E. obtusifolia. This strategy was accomplished through the following steps. (i) Separate the extract of E. obtusifolia into fractions by an autopurification system controlled by liquid chromatography with mass spectrometry. (ii) Determine the active fractions of E. obtusifolia by thin-layer chromatography bioautography. (iii) Identify the structure of the main active compounds with the information provided by direct analysis in real time mass spectrometry. (iv) Calculate the IC50 value of each compound against xanthine oxidase using high-performance liquid chromatography. Using the caulis of E. obtusifolia as the experimental material, seven target peaks were screened out as xanthine oxidase inhibitors or antioxidants. Our screening strategy allows for rapid analysis of small molecules with almost no sample preparation and can be completed within a week, making it a useful assay to identify unstable compounds and provide the empirical foundation for E. obtusifolia as a natural remedy for gout and oxidative-stress-related diseases.