Chemical composition and biological activity of extracts from Arrabidaea bilabiata

Abstract

Consumption of Arrabidaea bilabiata fresh leaves produces a paraplegic syndrome in cattle. For isolation of the active principle, isopropanol and methanol extracts were prepared from the aerial parts of the plant; these were administered to Sprague-Dawley rats at doses of 0.5, 1, and 2 mg/kg, orally, to determine the presence of substances affecting spontaneous motor activity. The isopropanol extract produced significant increases of long-pause and short-pause movements (112 and 54%, respectively). The methanol extract tended to increase motor activity, but the effect did not reach statistical significance. Chemical and spectroscopic analysis of the isopropanol extract showed allantoin was the major constituent. It was administered to rats, at doses of 1.2, 12, and 120 mg/kg. A complex dose-response curve was observed, but at the highest dose, there was a 52% increase in the number of long-pause movements. It was inferred that allantoin and the constituents of the alcoholic extracts might not be responsible for the paraplegic syndrome in cattle. The alteration of cattle motor activity could be caused by other non-alcoholic constituents. Additionally, extracts were assayed for in vitro activity against Escherichia coli, Klebsiella pneumonae, Pseudomonas aeruginosa, Staphylococcus aureus, Bacillus sp. and Candida albicans. All microbial strains were found to be resistant to the extracts with the exception of C. albicans, suggesting a possible antifungal activity.