Toxicity and therapeutic effects of zerumbone extract on complete freund’s adjuvant-induced rheumatoid arthritis rat model

The present study was conducted to investigate the antinociceptive and anti-arthritic effects of zerumbone in Complete Freund’s adjuvant induced Rheumatoid Arthritis model in rats. Zerumbone is a sesquiterpene isolated and purified from the rhizomes of Zingiber zerumbet plants, locally known as ‘lempoyang’. Zingiber zerumbet is one of the most important species of cultivated ginger, used in food flavouring. Zerumbone was obtained from the rhizomes through a sequence of isolation processes involving hydrodistillation, rotary evaporation of excessive solvents, column chromatography, and finally followed by recrystallization. The compound was subjected to thin layer chromatography (TLC), gas chromatography mass spectrometry (GC-MS) and high performance liquid chromatography (HPLC) to identify its chemical structure and purity. Zerumbone was optimally isolated using the hexane and ethyl acetate solvent system at a ratio of 8:2 with a total yield of 1.2%. In the present study, it was shown that intraperitoneal administration of zerumbone at doses of 10 mg/kg did not show any signs of toxicity in terms of behavioural changes, body weight, liver and kidneys, hematological and liver function parameters. The findings were further supported by histopathological observations of the liver and kidney that demonstrated normal histological architecture. Rheumatoid arthritis was induced by intraplantar injection of CFA on the right hind paw of each rat at day 0. Anti-inflammatory activity of zerumbone on the RA-induced rats was evaluated using plethysmometer test and paw swelling was assessed by measuring the thickness of the hind paw with a digital caliper. The determination of the antinociceptive profile of zerumbone on rheumatoid arthritisinduced model in rats was studied through thermal and mechanical threshold which consists of the Hargreaves plantar test, Von Frey test, and Randall-Selitto analgesiometer with slight modifications. During the experimental period, the body weight was recorded using a digital weighing balance every 3 days consecutively after CFA injection. With slight modifications, the visual arthritis scoring was used to assess behavioural changes through the ability to stance, mobility and flexion pain test. The clinical assessment of arthritis had been studied through cytokine concentrations and hematological parameters. As a conclusion, the study strongly confirms the antinociceptive and antiinflammatory activities of zerumbone as well as elucidated the possible mechanism of action through which it exerts its effects. In addition to that, the toxicity studies demonstrated the safety margin of zerumbone in mice, thus scientifically justifying the traditional use of this species of ginger and setting the path for future studies