Passibiflorin,epipassibiflorin and passitrifasciatin: cyclopentenoid cyanogenic glycosides from Passiflora

An epimeric mixture of two novel cyclopentenoid cyanogenic glycosides, passibiflorin [1-(6-O-β-D-rhamnopyranosyl-β-D-glucopyranosyloxy)-4-hydroxycyclopent-2-en-1-nitrile] and its C-1 epimer, epipassibiflorin, has been isolated from Passiflora biflora and P. talamancensis. The structures were determined by means of ¹H NMR and ¹³C NMR. Another novel cyclopentenoid cyanogenic glycoside, passitrifasciatin [1-(4-O-β-D-rhamnopyranosyl-β-D-glucopyranosyloxy)-4-hydroxycyclopent-2-en-1-nitrile] is described from Passiflora trifasciata. The structure was determined by means of ¹H NMR. The identification of the sugar moieties was made by HPLC and TLC. The isolation of a β-1 → 4 and a β-1 → 6-rhamnoglucoside of cyclopentenoid cyanogens from three species of subgenus Plectostemma of Passiflora suggests that diglycosides of this type are taxonomically diagnostic for the section.     

Co-occurrence of Valine/Isoleucine-derived and cyclopentenoid cyanogens in a Passiflora species

The valine/isoleucine-derived cyanogenic glycosides linamarin and lotaustralin have been isolated together with the cyclopentenoid cyanogen passibiflorin from Passiflora lutea. This is only the second report of the production of cyanogenic glycosides from more than one biosynthetic pathway in individuals of a single species.     

Triterpene glycosides related to quadranguloside from Passiflora quadrangularis

Two new cyclopropane triterpene glycosides were isolated from the methanol extracts of leaves of Passiflora quadrangularis. On the basis of hydrolysis, spectral evidence and comparison with quadranguloside, these compounds were assigned the structures 9,19-cyclolanosta-22,25-epoxy-3β-21,22(R)-triol-3β-O-gentiobioside and 9,19-cyclolanosta-21,24-epoxy-3β-25,26-triol-3β-O-gentiobioside,respectively. Oleanolic acid-3-sophoroside was also isolated for the first time from a natural source.     

Mobilization and utilization of cyanogenic glycosides: the linustatin pathway

In the seeds of Hevea brasiliensis, the cyanogenic monoglucoside linamarin (2-β-d-glucopyranosyloxy-2-methylpropionitrile) is accumulated in the endosperm. After onset of germination, the cyanogenic diglucoside linustatin (2-[6-β-d-glucosyl-β-d-glucopyranosyloxy]-2- methylpropionitrile) is formed and exuded from the endosperm of Hevea seedlings. At the same time the content of cyanogenic monoglucosides decreases. The linustatin-splitting diglucosidase and the β-cyanoalanine synthase that assimilates HCN, exhibit their highest activities in the young seedling at this time. Based on these observations the following pathway for the in vivo mobilization and metabolism of cyanogenic glucosides is proposed: storage of monoglucosides (in the endosperm)—glucosylation—transport of the diglucoside (out of the endosperm into the seedling)—cleavage by diglucosidase—reassimilation of HCN to noncyanogenic compounds. The presence of this pathway demonstrates that cyanogenic glucosides, typical secondary plant products serve in the metabolism of developing plants as N-storage compounds and do not exclusively exhibit protective functions due to their repellent effect.     

Gynocardin from Baileyoxylon lanceolatum and a revision of cyanogenic glycosides in Achariaceae

The cyclopentenone cyanhydrin glycoside gynocardin was the only cyanogen isolated from foliage of monotypic Australian rainforest tree, Baileyoxylon lanceolatum (Achariaceae). The presence of cyanogenic compounds in plants can have considerable taxonomic utility. A review of previous reports of cyanogenesis in the recently revised Achariaceae revealed distinct taxonomic patterns as well as inconsistencies in the reporting of cyanogenic compounds. This variation appears to be due to tissue level localisation of cyanogenic compounds as well as discrepancies in results obtained from different detection methods. Recommendations are made for future investigations.     

Two chromone-secoiridoid glycosides and three indole alkaloid glycosides from Neonauclea sessilifolia

From the dried roots of Neonauclea sessilifolia, two new chromone-secoiridoid glycosides, sessilifoside and 7"-O-beta-D-glucopyranosylsessilifoside, and three novel indole alkaloid glycosides, neonaucleosides A, B, and C, were isolated along with the main known glycosides, 5-hydroxy-2-methylchromone-7-O-beta-D-apiofuranosyl-(1-->6)-beta-D-glucopyranoside, sweroside, loganin, grandifloroside, and quinovic acid 3 beta-O-beta-D-quinovopyranoside-28-O-beta-D-glucopyranoside. The structures of these new glycosides were determined by spectroscopic and chemical means. Neonaucleoside A and its C-3 epimer were prepared from secologanin and tryptamine.     

Two chromone glycosides from Cassia multijuga

Two new 2-methylchromone glycosides have been identified in the leaves of Cassia multiluga.     

Two flavonoid glycosides from Chenopodium murale

Two new triglycosides, kaempferol-3-O-[(4-beta-D-apiofuranosyl)-alpha-L- rhamnopyranoside]-7-O-alpha-L-rhamnopyranoside and kaempferol-3-O-[(4-beta-D-xylopyranosyl)-alpha-L-rhamnopyranoside]-7-O- alpha-L-rhamnopyranoside were isolated from the methanol extract of Chenopodium murale, together with a known diglycoside, kaempferol-3-O-beta-D-glucopyranoside-7-O-alpha-L-rhamnopyranoside. The characterization of the three compounds was achieved by various spectroscopic methods.     

Two flavone glycosides from Sideritis leucantha

8-Hydroxyluteolin occurs in Sideritis leucantha as the 7-(2″-allosylglucoside) and the 8-glucoside of its 6,7-dimethyl ether has also been characterized from the same plant.     

Two iridoid glycosides from Campsidium valdivianum

Besides stansioside and plantarenaloside, the aerial parts of Campsidium valdivianum contain two new iridoid diglucosides, stansiosigenin 1-O-β-gentiobioside and plantarenalosigenin 1-O-β-gentiobioside.     

Absence of cyanogenic glycosides in the tribe Miconieae (Melastomataceae)

In order to compare ant and non-ant defended species of Melastomataceae, production of hydrogen cyanide gas was tested in the field for 51 species of 10 genera of the tribe Miconieae. Using both the picric acid and the Feigl–Anger tests all populations surveyed tested negative for the presence of cyanogenic glycosides. These results confirm that cyanogenesis is rare in the family, although not completely absent. Cyanogenic glycosides are not responsible for the protection against herbivory in non-ant defended species, but this does not rule out that there are quantitative of qualitative differences in other secondary metabolites.     

Two new flavone glycosides from Cirsium lineare

An examination of four species of Cirsium disclosed the presence of two new flavonoids in C. lineare. The structure of one was 5,4′-dihydroxy-6,7,3′-trimethoxyflavone (cirsilineol) 4′-monoglucoside and the other 5,3′,4′-trihydroxy-6,7-dimethoxyflavone (cirsiliol) 4′-monoglucoside. Luteolin 7-glucoside was found in C. suffultum, and pectolinarin and linarin in C. kamtschaticum and C. pectinellum.     

Two flavonol glycosides from Vancouveria hexandra.

In addition to two known glycosides, ikarisoside F and epimedin A, two new glycosides of a flavonol with a gamma, gamma-dimethylallyl group were isolated from the underground and the aerial parts of Vancouveria hexandra. The structures were determined to be des-O-methylanhydroicaritin 3,7-diglucoside and anhydroicaritin 3-glucosyl (1----3)rhamnoside-7-glucoside by means of spectral analysis.     

Two flavonol glycosides from Chenopodium quinoa.

Two new flavonol glycosides from the seeds of Chenopodium quinoa have been isolated. Their structures were established as kaempferol 3-apiofuranosyl(1"'----2")rhamnopyranosyl(1"----6")galactoside and kaempferol 3-apiofuranosyl(1"'----2")rhamnopyranosyl(1"----6")galactoside. The main flavonoid glycoside was kaempferol 3-(2,6-dirhamnopyranosyl)galactoside.     

Two phenylpropanoid glycosides from Leonurus glaucescens.

Two new phenylpropanoid glycosides, leonosides A and B, and two known glycosides lavandulifolioside and verbascoside, were isolated from the aerial parts of Leonurus glaucescens. On the basis of chemical and spectral evidence, leonosides A and B were shown to be beta-(3,4-dihydroxyphenyl)-ethyl-O-alpha-L-arabinopyranosyl-(1---- 2)-alpha-L- rhamnopyranosyl-(1----3)-4-O-feruloyl-beta-D-glucopyranoside and beta-(3-hydroxy, 4-methoxyphenyl)-ethyl-O-alpha-L-arabinopyranosyl-(1----2)- alpha-L-rhamnopyranosyl-(1----3)-4-O-feruloyl-beta-D-glucopyranosi de, respectively.