A methanolic extract of Rubus idaeus leaves, when fractionated by column chromatography, yielded two distinct bands containing compounds that demonstrated in vitro, dose dependent, smooth muscle relaxant activity using transmurally-stimulated Guinea pig ileum preparations. From band two, following extensive chromatographic separation, several compounds with smooth muscle relaxant activity were obtained, one of which was characterized, from spectroscopic and mass spectrometric data, as 1- O-(1,2-dihydroxyethyl)-4- O-methoxy-β-D-glucopyranosyl-(1→3)-β-D-glucopyranoside.