ISOLATION OF PHARMACOLOGICALLY ACTIVE BENZODIAZEPINE RECEPTOR LIGANDSFROM TILIA-TOMENTOSA (TILIACEAE)

Tilia species are traditional medicinal plants widely used in Latin Am erica as sedatives and tranquilizers. For this purpose, the infusion o f their inflorescences is used to prepare a tea. In this study extract s of inflorescences from Tilia tomentosa Moench, one of the species fo und in the market, were purified using a benzodiazepine (BZD) binding assay to detect BZD receptor ligands in the different fractions. One o f the ligands was identified as kaempferol, but it had low affinity (K -i = 93 mu M) for this receptor, and did not produce sedative or anxio lytic effects in mice. On the other hand, a complex fraction, containi ng as yet unidentified constituents, but probably of a flavonoid natur e, when administered intraperitoneally in mice, had a clear anxiolytic effect in both the elevated plus-maze and holeboard tests, two well v alidated pharmacological tests to measure anxiolytic and sedative comp ounds. This active fraction had no effect on total and ambulatory loco motor activity. In conclusion, our results demonstrate the occurrence of active principle(s) in, at least, one species of Tilia that may exp lain its ethnopharmacological use as an anxiolytic.