Analgesic principle from Curcuma amada

Ethnopharmacological relevanceThe rhizome of Curcuma amada has been used as a folk medicine for the treatment of rheumatic disorders in the northern part of Bangladesh and has also used for the treatment of inflammation and fever in the Ayurvedic and Unani systems of medicine. Aim of the study was to investigate the analgesic principle of the MeOH extract of the rhizome of Curcuma amada by an in vivo bioassay guided chromatographic separation and purification, and the structure elucidation of the purified compound by spectroscopic methods.Materials and methodsDried powder of Curcuma amada rhizomes was extracted with MeOH. The analgesic activity of the crude extract and its chromatographic fractions as well as the purified compound itself was evaluated by the acetic acid induced writhing method and the formalin induced licking test in Swiss albino mice. The MeOH extract was separated by chromatographic methods and the pure active compound was purified by crystallization in hexanes. The structure of the pure compound was then elucidated by spectroscopic methods.ResultsThe MeOH extract of Curcuma amada exhibited 41.63% and 45.53% inhibitions in the acetic acid induced writhing method at doses of 200 mg/kg and 400 mg/kg, respectively. It also exerted 20.43% and 28.50% inhibitions in early phase at doses of 200 mg/kg and 400 mg/kg, respectively, and 30.41% and 42.95% inhibitions in late phase at doses of 200 mg/kg and 400 mg/kg, respectively in the formalin induced licking test. Vacuum Liquid Chromatography (VLC) of crude extract yielded five fractions and Fr. 1 was found to have the most potent analgesic activity with inhibitions of 36.96% in the acetic acid induced writhing method and 47.51% (early phase), 39.50% (late phase) in the formalin induced licking test at a dose of 200 mg/kg. Column chromatography of Fr. 1 on silica gel generated seven fractions (SF. 1–SF. 7). SF. 2 showed the most potent activity with inhibition of 49.81% in the acetic acid induced writhing method at a dose of 100 mg/kg. Crystallization of SF. 2 yielded (1) (zederone, 520 mg). It showed statistically significant inhibitions of 38.91% and 52.14% in the acetic acid induced writhing method at doses of 20 mg/kg and 40 mg/kg, respectively. Moreover, it also showed statistically significant inhibitions of 27.79% and 29.93% (early phase) and of 38.24% and 46.08% (late phase) in the formalin induced licking test at doses of 20 mg/kg and 40 mg/kg, respectively.ConclusionIsolation and characterization of zederone (1) as analgesic principle of Curcuma amada corroborate its use in Ayurvedic, Unani and folk medicines for the treatment of rheumatic disorders and also contributing to its pharmacological validation.

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