Isoflavonoid Glycosides from the Rhizomes of Iris germanica.

Plants of the genus Iris (Iridaceae) have been previously recognized as rich sources of secondary metabolites, [1][2][3][4] and comprise over 300 species.Some of these are ornamental, and among them, 16 species are found in Pakistan.5,6) Previous phytochemical investigations of the Iris plants have resulted in the isolation of a variety of compounds including flavonoids, isoflavonoides and their glycosides, benzoquinones, triterpenoids and stilbene glycosides.1,5,7) The compounds isolated from these species were reported to have piscicidal, antineoplastic, antioxidant, anti-tumor, antiplasmodial, and antituberculosis properties.[8][9][10] Iris germanica L. is widely distributed in most parts of the world, and is also cultivated as an ornamental plant.Rhizomes of the plant yield an essential oil which is used in perfumes and cosmetics, while the leaves are a rich source of ascorbic acid and vitamins.6) A number of secondary metabolites from I. germanica have been reported earlier.8,9,11) Results and DiscussionThe present work on the methanolic extracts of the rhizomes of Iris germanica of Turkish origin has resulted in the isolation and characterization of two new compounds 1 and 2, along with two known compounds 3 and 4. 11,12) Germanaism A (1) was isolated as a white amorphous solid.A pseudo-molecular ion peak was observed at m/z 505.1342 (M ϩ ϩH) in the high resolution Fast Atom Bombardment (HR-FAB)-MS (ϩve), consistent with the formula C 24 H 25 O 12 (Calcd C 24 H 25 O 12 : 505.1345).FAB-MS also showed an ion at m/z 343 (M ϩ ϪC 6 H 11 O 5 ) resulting from the loss of a hexose moiety.The electron impact (EI)-MS showed fragments at m/z 147 and 194 due to retro Diels-Alders cleavage of the aglycone part of compound 1.Strong IR absorptions at 1649 (CϭO), 1559 (aromatic CϭC), 3328 (OH) and 940 (OCH 2 O) cm Ϫ1 , along with a broad C-O stretching band in the region 1045-1267 cm Ϫ1 suggested the presence of a sugar moiety.Characteristic UV absorptions at 263 (band II) and 319 (band I) nm indicated the presence of a 5,4Ј-isoflavone skeleton.13)The 1 H-and 13 C-NMR spectra (DMSO-d 6 , 500 MHz) of 1 showed a number of signals characteristic of sugar and isoflavone moieties.14,15) The 1 H-NMR spectrum showed singlets at d 7.89 (H-2) and 6.52 (H-8) characteristic of a benzopyrane moiety.H-2Ј appeared as a doublet at d 7.07 (d, J 2Ј,6Ј ϭ2.0 Hz), showing meta coupling with H-6Ј which res-* To whom correspondence should be addressed.