Muscarinic Receptor Activity of Some Malaysian Plant Species

Muscarinic receptor binding activity was tested on 224 plant extracts obtained from more than 50 plant families found in Malaysia. The plant extracts were evaluated by a 96-well microplate filtration-based radioligand competitive assay, centered on the ability of the plant extracts to competitively displace the radioligand, [H-3]N -methylscopolamine, from binding to the muscarinic membrane receptors. The screening assay was initially carried out at 50 mu g/assay point, and those showing inhibition at and above 61% were retested at 10 mu g/assay point. The extracts of Ficus septica Burm. f. (Moraceae) [65.85 +/- 3.75% inhibition; mean (n = 3)+/- SD], Polyalthia microtus Miq. (Annonaceae) (32.63 +/- 1.38% inhibition), and Popowia odoardoi Diels (Annonaceae) (35.7 +/- 97.11% inhibition) at 10 mu g/assay point exhibited muscarinic properties, which are worthy of further investigation.