Besides 7-(2-O-B-Dglucuronyl-B-Dglucuronyloxy)-5,3',4'-trihydroxytlavone, scutellarin, rosmarinic acid and caffeic acid, two cyanogenic glycosides have been isolated from the dried leaves of Perillafrutescens var. acuta. One of them is prunasin and the other is (R)-2-(2-0-~-~glucopyranosyl-B_Dglucopyranosyloxy~phenylacetonit~le, a new isomer of amygdalin.Perilla frutescens B&t. var. acuta Kudo (Japanese name; Shiso), an annual medicinal herb of Iabiatae [l, 23, is important in Japanese cooking, as one of the popular garnishes and as a food colourant. A tradition that, prior to the application as a colourant, the leaves are treated with table-salt to remove the harshness, suggests the existence of some water-soluble principles in addition to llavonoids which have already been studied by Ishikura c31- On chromatographic isolation, the methanolic extract of the dried leaves provided two non-phenolic compounds, 1 and 2, besides four phenolics, i.e. 7-(2-O-/?-~ glucuronyl-/LD-glucuronyloxy)-5,3',4'-trihydroxyflavone [4], scutellarin, rosmarinic acid and caffeic acid. The elementary analyses, FDMS [S] and FABMS [6] assigned the formulae CZOHZ,O,,N for 1 and C1,H1,O,N for 2. The intense fragment ion at m/z 116 in FDMS and FABMS of both compounds might well be ascribed to [C6H5CHCN]+. In harmony with the IR (C-O at around 1000-l 100 cm-') and 'H NMR data [five aromatic, one benzylic and fourteen (seven in 2) sugar protons], this indicates that 1 and 2 are di- and mono-hexosides of the same aglycone. Indeed 1 was hydrolysed with Nhydrochloric acid to 2 and D-glucose.Compound 2 was further hydrolysed with concentrated hydrochloric acid to (R)-mandelic acid, ammonium salt and glucose. Enzymic hydrolysis of 2 with j?-glucosidase provided benzaldehyde, hydrogen cyanide and glucose. From these results and by comparison with literature data [7-9],2 was identified as (R)-2-(B-D-glucopyranosyloxy) phenylacetonitrile (prunasin).In the 13C NMR spectrum of 1 the signals due to the aglycone were practically superimposable with those of 2.Of sugar signals, the ones assignable to C-2 and C-l of the inner glucose were respectively shifted downfield by + 8.5 ppm and upfield by - 1.1 ppm than those in 2, indicating the 1 + 2 linkage between the two glucose moieties. Two anomeric proton signals were detected in the 'H NMR spectrum of 1 as two doublets at 64.96 and 5.12, whose coupling constants (J = 6 Hz) indicated the b-configuration for both glycosidic linkages. Since on acidic hydrolysis of amygdalin and prunasin the steric configuration at C-2 remained unchanged [7], it is not unreasonable to assume that 1 has the same chiral center as 2. Compound 1 is that (R)-2-(2-0-fi-D-glucopyranosylb-Dglucopyranosyloxytphenylacetonitrile, a position isomer of amygdalin. This constitutes the first report of cyanogenic glycosides in the Labiatae.