Inhibiting Activity of Some Glucoindolalkaloids and Iridoids from Sickingia williamsii on Electrically Induced Contractions of Isolated Guinea-pig Ileum

The present study examined the effects of the extracts (petroleum ether, CHCl₃, CHCl₃/MeOH (9:1) and MeOH), partially purified fractions and pure compounds (mainly alkaloids and iridoids) from Sickingia williamsii on the electrically induced contractions of the isolated guinea-pig ileum. The results of our experiments indicate that CHCl₃/MeOH (9:1) and CHCl₃ extracts, tested at concentrations of 300, 150 and 30 μg/mL, dose-dependently reduced the guinea-pig ileum electrical contractions, whereas MeOH and petroleum ether extracts did not affect it. Furthermore, both the partially purified fractions I–IV each tested at concentrations of 500, 250 and 100 μg/mL from the CHCl₃/MeOH (9:1) extract and some pure compounds (10^?4 M , 5×10^?5 M and 2.5×10^?5 M ) isolated and purified from the above fractions significantly reduced, in a dose dependent manner, the electrical contractions of the ileum. As the active pure compounds possess an indole nucleus or/and an iridoid nucleus in their structures, the inhibitory effects appear to depend on these structures.