A comparative study on the antioxidant activity of Zingiberis Rhizoma raw herb and granule

Introduction: Zingiberis Rhizoma is traditionally used to treat atherosclerosis, arthritis and rheumatologic complications. Zingiberis Rhizoma contains phenolic bioactives including gingerols and shogaols, which are well-known antioxidants. Recently, there is growing trend towards the clinical use of herbal granules due to their portability, and ease of storage and administration. The aim of this study was to compare the antioxidant activity of Zingiberis Rhizoma granules to its raw herb decoction. Methods: Five raw herbs were extracted in water using heat reflux for 1 h. The water extracts and 9 granule samples were further extracted in ethyl-acetate using sonication for 0.5 h. Modified methods for the 2,2-diphenyl-1-picrylhydrazyl (DPPH) radical scavenging and total phenolic content (TPC) by Folin-Ciocalteu assays were used to estimate the antioxidant capacity of the extracts and results were reported as the gallic acid equivalent (GAE). Results: Hierarchical cluster analysis shows distinct raw and granule groups (except for one raw extract). The radical scavenging activities of the raw herb extracts (2.45 ± 0.47 mg GAE/g DE) were significantly higher (p < 0.05) than the granule extracts (87.77 ± 27 mg GAE/g DE) and this was positively correlated to the TPC (r = 0.98, p < 0.01). Conclusions: Overall, Zingiberis Rhizoma raw herb extracts possessed greater antioxidant activity than granules. The standardisation of granules and further pharmacological and clinical studies are warranted to determine the dosage regime of Zingiberis Rhizoma granules.