Antinociceptive principle from Curcuma aeruginosa

The rhizome of Curcuma aeruginosa Roxb (Zingiberaceae) has been used as a traditional folk medicine for the treatment of rheumatic disorders in Bangladesh. The aim of the current study was the bioassay-guided isolation and purification of an antinociceptive principle from the methanol extract of C. aeruginosa rhizomes.

The antinociceptive activity was determined using acetic acid induced writhing and formalin induced licking in the Swiss albino mice to investigate central and peripheral antinociceptive principle of C. aeruginosa rhizomes. Vacuum Liquid Chromatography (VLC) and open column chromatography were used for separation. Crystallization was used for the purification of the isolated compound germacrone (1). Diclofenac (10 mg/kg) and aspirin (100 mg/kg) were used as positive control and 5 % carboxymethyl cellulose (CMC) in distilled water (10 ml/kg) for negative control were used in the acetic acid induced writhing and formalin induced licking methods.

The methanol extract exhibited 37.50 and 45.31 % inhibition of writhing; 33.27 and 38.13 % inhibition of licking in the first phase and 69.72, 73.71 % inhibition of licking in the second phase at doses of 200 and 400 mg/kg, respectively. VLC of the extract yielded five fractions (Fr. 1 to Fr. 5). Fr. 1 exhibited 33.98 % inhibition that was comparably higher than other fractions (Fr. 2 to Fr. 5) at a dose of 100 mg/kg. Column chromatography of Fr. 1 generated five fractions (SF. 1 to SF. 5). Fraction SF.3 exhibited 46.88 % inhibition that was most potent among the other fractions at a dose of 50 mg/kg. Crystallization of the fraction SF.3 yielded germacrone (1), a cyclic sesquiterpene. Germacrone (1) showed 22.66, 34.77 and 51.17 % inhibition of writhing at doses of 10, 20 and 40 mg/kg, respectively; 30.43 and 37.53 % inhibition in the initial phase and 32.27 and 60.96 % inhibition in the second phase of licking at doses of 200 and 400 mg/kg, respectively.

Germacrone (1) showed a potent activity in both writhing and licking methods that indicates the compound as a central and peripheral antinociceptive principle of C. aeruginosa rhizomes with possible anti-inflammatory activity.