Standardization and xanthine oxidase inhibitory potential of Zanthoxylum armatum fruits

Abstract

Ethnopharmacological relevance: Tejovati (Zanthoxylum armatum DC; Family- Rutaceae) popularly known as toothache tree is widely distributed in sub-tropical Himalaya region. Traditionally, The Southeast Asian population of Indo-Nepal origin uses it to treat asthma, gout, pain, and inflammation. The Ayurvedic action of the plant includes the balancing of Vata-Kapha in the body. Which lead to various ailments related to the circulation of blood and water, digestion, immunity, and skin. Therefore, in-vitro xanthine oxidase (XO) inhibition potential of the extract could be worth to explore prospect in the prevention/treatment of gouty affections of the joints and other diseases.

Aim of study: Anti-inflammatory and antioxidant potential of Z. armatum fruit (ZAF) has been reported. To date, no scientific study to validate the claim for gout treatment/management has been attempted so far. The present study deals with the xanthine oxidase inhibitory potential of a various extract of ZAF and marker-based high-performance liquid chromatography (HPLC) standardization of most active fraction.

Materials and methods: Liquid-liquid partioning of crude methanol extract of the ZAF followed by repeated column chromatography of most active fraction has resulted in the isolation of seven compounds. Five distinct groups of compounds were isolated, purified, and identified. We have investigated the therapeutic action of ZAF in the management of gout through in-vitro assay of XO, a key enzyme involved in gout pathogenesis.

Results: Phytochemical investigation of ZAF has resulted in the isolation of seven compounds of diverse nature. It is noteworthy to mention that out of seven, five compounds have shown the xanthine oxidase inhibitory action. The ethyl acetate fraction was most potent to inhibit XO. The XO inhibitory activity (IC₅₀ values) of isolated marker chemical was ranging from 5.62 to 41.21 µM. Three compounds viz. acetyl phenyl acetate (ZA-2), prudomestin (ZA-6), and tambulin (ZA-7) showed the most potent XO inhibitory activity (IC₅₀ ≈ 6 µM) comparable with a positive control (Allopurinol, IC₅₀, 3.38 µM). This is the first validated HPLC-PDA method for simultaneous analysis and accurate quantification of seven compounds (phenolic acid, acetyl phenyl acetate, xylopyranoside, diphenyl ether and three flavones) in ZAF as well as their distribution in other tissues of the plant.

Conclusion: Most potent three chemicals (ZA-2, 6 and 7) could be considered as bioactive to ensure the robust quality of the enriched fraction of ZAF with defined XO inhibition potential. Therefore, either single purified component or their enriched fraction could be a better choice for the management of gout than the crude extract of ZAF. Developed HPLC method is suitable for quality assurance analysis and process control of ZAF derived product intended for gout management. XO inhibitory potential exhibited by the characterized compounds validate the traditional use of this ZAF for the treatment of gout. Further, a detailed study is required to assess the effect of ZAF chemicals on serum uric acid and mechanism of XO inhibition.

Keywords: Acetyl phenyl acetate (PubChem CID:31229); Gallic acid (PubChem CID: 370); Gout; Ombuin (PubChem CID: 5320287); Phytopharmaceutical; Polyphenols; Prudomestin (PubChem CID: 10404353); Quality control; Tambulin (PubChem CID: 5281700); Validated HPLC method.