Comparative study of the analgesic effect of different phenylethanoid-based fractions from Plantago lanceolata L

The present study aims to compare the analgesic effect of 3 phenylethanoid-based phytocomplexes obtained by methanol extraction of the herb, liquid-liquid distribution with ethyl acetate and CC on Celite 545, butanol as eluent: phenylethanoid-flavonoidic (PF) fraction (49.5% acteoside, 11.6% luteolin-7-glucoside, free of iridoids), phenylethanoid (P) fraction (46.6% acteoside) and phenylethanoid-iridoidic (PI) fraction (48.8% acteoside, 4.9% catalpol, 7.8% aucubin, free of flavonoids). The compounds were quantified by HPLC and the absence of flavonoids and iridoids was confirmed by negative colour reactions with specific reagents. The potential analgesic activity was evaluated on mice (2 testing groups and one blank control group, 10 mice each for every experiment) using acetic acid-induced writhing test and hot-plate test. The extracts were given to mice at doses of 100mg and 400mg/kg i.p and jump and licking parameters were evaluated at 15, 30, 60, 120 minutes, comparative to control group. Statistical analysis was performed with the Student's t-test. The results for PF fraction were statistical significant in the hot-plate test for the jump parameter at 60min at the dose of 400mg/kg (p<0.05). The most significant activity was shown in the hot-plate test for P fraction that had a rapid analgesic effect at 15min at the dose of 100mg/kg for the jump parameter. The effect was prolonged for 120min (p<0.05). The analgesic effect was also observed in the writhing test at 30 and 60min (p<0.05). PI fraction showed an analgesic effect in the hot-plate test for the jump parameter at 30min and also in the writhing test at 30 and 60min at a dose of 100mg/kg (p<0.05).These results show that the phenylethanoid fraction have the most rapid and prolonged analgesic effect comparing to phenylethanoid-flavonoidic and phenylethanoid-iridoidic fractions. The data suggest that flavonoids and iridoids have no positive influence on the analgesic effect induced by phenylethanoids.