Chalcones and other flavonoids from Asarum sensu lato (Aristolochiaceae)

Seventy-five taxa belonging to the genus Asarum sensu lato were studied for their composition of flavonoids. Three chalcones and an aurone were found as major components. The chalcones were identified as chalcononaringenin 2′,4′-di-O-glucoside, 4,2′,4′-tri-O-glucoside, 4-O-glucoside, and the aurone as aureisidin 4,6-di-O-glucoside. The glycoside, 2′,4′-di-O-glucoside was detected in all taxa examined, and is a chemotaxonomical feature of Asarum sensu lato. 4,2′,4′-Tri-O-glucoside was found from the taxa classified into the genera Asiasarum, Geotaenium and Heterotropa by Maekawa's system. On the other hand, the glycoside was not detected from three Asarum sensu stricto species, A. caudigerum, A. caulescens and A. leptophyllum. In contrast, aurone, aureusidin 4,6-di-O-glucoside occurred in two Asarum s.s., A. caulescens and A. leptophyllum. Thus, the Asarum s.s. and other Maekawa's genera, Asiasarum, Geotaenium and Heterotropa could distinguish by the presence or absence of some anthochlor pigments. Other flavonoids were isolated from the selected 18 Asarum species. They were characterized as some flavonol 3- or 3,7-O-glycosides based on kaempferol, quercetin and isorhamnetin, flavone, apigenin 6,8-di-C-glycoside, flavanone, naringenin 5,7-di-O-glucoside, and xanthone, mangiferin.     

The status of Asarum marmoratum (Aristolochiaceae)

Asarum marmoratum Piper, a species with marbled leaves from southern Oregon and northern California, differs fromA. hartwegii. S. Wats. in many respects, and should be recognized as distinct. The species is described, illustrated, and compared to the four other western North American species ofAsarum in a synoptic key.     

Asarum yentuense sp. nov. (Aristolochiaceae) from Vietnam

A new species, Asarum yentuense N. Tuan & Sasamoto (Aristolochiaceae), is described from Quang Ninh Province, Vietnam. This species belongs to A. subgen. Heterotropa sect. Longistylis and is most similar to Asarum petelotii, A. glabrum, A. reticulatum and A. magnificum var. dinghuense, but is differentiated by morphology, including the length of the calyx tube and lobes, and phenology.     

Self-pollination of Asarum caulescens Maxim. (Aristolochiaceae) in Japan

Abstract Observations in two populations of Asarum caulescens belonging to sect. Asarum indicate that inbreeding predominates becuase (1) no effective pollinator was observed, (2) bagged flowers set fruits with well-swollen seeds, and (3) the behaviour of filaments, changing from recurved to straight posture, results in direct deposition of pollen grains on the stigmas. This result agrees with reports on three other species of sect. Asarum in Europe and North America. We suggest that species of sect. Asarum diverged from an autogamous ancestor.     

flavonol glycosides from Callitris Glauca

From the leaves of Callistris glauca myricetin 7-arabinoside, quercitrin, kaempferol 5-rhamnoside, a quercetin arabinoside, quercetin, kaempferol, galangin and shikimic acid were isolated. The natural occurrence of myricetin 7-arabinoside has not previously been reported.     

Eight flavonol glycosides in Pyrola (pyrolaceae)

As part of a general survey of the flavonoids of Pyrolaceae, the flavonoids of Pyrola virens and P. chlorantha were investigated. Eight flavonol glycosides based upon kaempferol, quercetin and rhamnetin were identified from each of the two species. Two of the glycosides, rhamnetin 3,3′,4′-tri-O-glucoside and rhamnetin 3-O-arabinoside-3′,4′-di-O-glucoside are previously unreported and further, represent an unusual pattern of glycosylation. The similarity of flavonoids and the presence of the unusual substitution pattern supports a conspecific status for the two taxa.     

Further flavonol glycosides from Anthyllis onobrychioides

The new triglycoside rhamnetin 3-O-β-d-galactopyranoside-3′,4′-di-O-β-d-glucopyranoside has been isolated from the aerial parts of Anthyllis onobrychioides. Two other new flavonol glycosides, rhamnazin 3-O-galactoside and rhamnazin 3-O-galactoside-4′-O-glucoside, were identified but not isolated as pure substances.     

Acylated flavonol glycosides from Delphinium staphisagria

An ethanolic extract of the aerial parts of Delphinium staphisagria L. from Tenerife yielded four new flavonol glycosides 2″-acetylastragalin, 2″-acetylpaeonoside, quercetin 3-O-(2-acetyl-β-glucopyranoside)-7-O-β-glucopyranoside and 2″-acetylpetiolaroside in addition to astragalin, isoquercitrin, paeonoside, kaempferol 3-O-β-glucopyranoside-7-O-α-rhamnopyranoside, petiolaroside and rutin.     

A cladistic analysis of Asarum (Aristolochiaceae) and implications for the evolution of herkogamy

A cladistic analysis of Asarum was conducted to examine relationships among species within the genus and to test the monophyly of several groups of taxa that have often been treated as segregate genera. Thirty-two species were drawn from throughout the range of the genus, representing a broad sample of sections and all segregate genera. The data matrix included 37 characters derived from various aspects of vegetative and floral morphology. A strict consensus of all most parsimonious trees suggests that Asarum s.l. is monophyletic and consists of two main clades: an Asarum clade, which is characterized by connate styles and inferior ovaries, and an Asiasarum-Hexastylis-Heterotropa clade, which is characterized by ridges on the inner perianth surface, dorsal stigmas, and bifid style extensions. The latter is a large and morphologically diverse clade that includes the North American segregate Hexastylis and two Asiatic segregates. Examination of pollination mechanisms in the context of this phylogeny supports the conclusion that herkogamy, and thus obligate insect pollination, is derived from a plesiomorphic condition of autonomous self-pollination. Associated with herkogamy are characters such as glandular trichomes and other ornamentation of the surface of the calyx that probably represent increased specialization to attract insect pollinators. This study also indicates that chromosomal evolution has occurred via aneuploid decrease from an ancestral chromosome number of 2n = 26 to 2n = 24 in Heterotropa. The recognition of two subgenera, subgenus Asarum and subgenus Heterotropa, corresponding to the two clades in the cladistic analysis, is recommended.     

Molecular phylogeny and taxonomic implications of Asarum (Aristolochiaceae) based on ITS and matK sequences

The genus Asarum (Aristolochiaceae) encompasses approximately 120 species from five sections. Taxonomic controversies concerning the genus Asarum and/or its intrageneric classification remain unresolved. In particular, sect. Heterotropa accounts for a large percentage of the genus (80 of 120 species) and is well diverged in the Sino–Japanese Forest subkingdom. Reconstruction of Heterotropa phylogeny and estimation of its divergence times would provide significant insight into the process of species diversity in the Sino–Japanese floristic region. This study encompassed 106 operational taxonomic units (OTUs), and phylogenetic analyses were conducted based on internal transcribed spacer (ITS) and matK sequences. Although the matK sequences provided informative results solely for section Geotaenium, phylogenetic trees based on ITS regions yielded a clear result for several sections. Three sections, Asarum, Geotaenium and Asiasarum, were supported as robust monophyletic groups, whereas Heterotropa had low support. Sect. Hexastylis was revealed to be polyphyletic, suggesting taxonomic reconstruction would be needed. Sect. Heterotropa comprises two clades, which correspond to species distribution ranges: mainland China and the island arc from Taiwan to mainland Japan via the Ryukyu Islands. It is notable that the common ancestry of the latter clade in the eastern Asian islands was highly supported, suggesting that the present species diversity of Heterotropa was initially caused by allopatric range fragmentation in East Asia.     

Acylated flavonol glycosides from the forage legume, Onobrychis viciifolia (sainfoin)

Ten acylated flavonol glycosides were isolated from aqueous acetone extracts of the aerial parts of the forage legume, Onobrychis viciifolia, and their structures determined using spectroscopic methods. Among these were eight previously unreported examples which comprised either feruloylated or sinapoylated derivatives of 3-O-di- and 3-O-triglycosides of kaempferol (3,5,7,4'-tetrahydroxyflavone) or quercetin (3,5,7,3',4'-pentahydroxyflavone). The diglycosides were acylated at the primary Glc residue of O-α-Rhap(1→6)-β-Glcp (rutinose), whereas the triglycosides were acylated at the terminal Rha residues of the branched trisaccharides, O-α-Rhap(1→2)[α-Rhap(1→6)]-β-Galp or O-α-Rhap(1→2)[α-Rhap(1→6)]-β-Glcp. Identification of the primary 3-O-linked hexose residues as either Gal or Glc was carried out by negative ion electrospray and serial MS, and cryoprobe NMR spectroscopy. Analysis of UV and MS spectra of the acylated flavonol glycosides provided additional diagnostic features relevant to direct characterisation of these compounds in hyphenated analyses. Quantitative analysis of the acylated flavonol glycosides present in different aerial parts of sainfoin revealed that the highest concentrations were in mature leaflets.     

Life-history monographs of Japanese plants. 12: Asarum caulescens Maxim. (Aristolochiaceae)

The life-history characteristics of Asarum caulescens Maxim. (Aristolochiaceae) are described here. This typical summer-green perennial of the Aristolochiaceae is a unique woodland element distributed in central Honshu, that is, south of Fukushima Prefecture to Shikoku and Kyushu, Japan. It grows in the somewhat shady understory of temperate montane deciduous broad-leaved or mixed forests associated with conifers, such as Cryptomeria japonica and Abies firma . One of the unique features of A. caulescens is its rhizome structures in combination with aerial shoots, which play an important role in vegetative propagation. The perennation strategy of A. caulescens is exceedingly complex, producing various combinations of linear or branched rhizomes bearing different numbers of leaves. Rhizomes consist of two or three segments, each 5 mm to 5 cm long as a unit, connected linearly, but also occasionally branched. At the tip of the newly formed rhizome segment, a single leaf or a pair of cordate leaves are formed. Exceedingly complex branching patterns of the rhizome segments were also recognized, forming ramets in late June to early July. Vegetative propagation by ramet formation obviously plays a very important role in the maintenance of local populations.     

Three new flavonol glycosides from Nervilia fordii

Three new flavonol glycosides, nervilifordizins A–C (1–3), were isolated from the whole plant of Nervilia fordii. Their structures were elucidated as rhamnazin 3-O-β-d-xylopyranosyl-(1→4)-β-d-glucopyranoside (1), rhamnazin 3-O-β-d-glucopyranosyl-(1→4)-β-d-glucopyranoside (2) and rhamnazin 3-O-β-d-xylopyranosyl-(1→4)-β-d-glucopyranoside-4′-O-β-d-glucopyranoside (3) on the basis of extensive spectroscopic analysis, including HSQC, HMBC, ¹H–¹H COSY, and chemical evidences.     

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.     

Antioxidant properties of flavonol glycosides from tea

Abstract

We have determined the antioxidant activity of the major flavonols found in tea: a monoglycoside, a diglycoside and two triglycosides of kaempferol and three monoglycosides, a diglycoside and two triglycosides of quercetin. The Trolox equivalent antioxidant capacity (TEAC) and inhibition of iron/ascorbate-induced lipid peroxidation of phosphatidyl choline vesicles were measured. In the aqueous phase TEAC assay, the quercetin monoglycosides and diglycoside were approximately half as effective as quercetin aglycone. The quercetin triglycosides were much less effective than the mono-glycosides and the diglycoside. The kaempferol glycosides were 32–9% less effective in the aqueous phase antioxidant assay compared to the kaempferol aglycone. Quercetin monoglycosides and diglycoside were potent inhibitors of lipid peroxidation, in contrast to the triglycoside which was much less effective. All the kaempferol glycosides were significantly less potent inhibitors of lipid peroxidation compared to the kaempferol aglycone. The compounds described herein demonstrate the antioxidant activity of the major flavonols in tea and indicate the effect of substituting a range of sugar moieties in the phenolic C ring.     

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.     

Four flavonol glycosides from Achlys triphylla.

Four new flavonol glycosides were isolated from the underground parts of Achlys triphylla in addition to eight known compounds. By means of spectroscopic analysis, the structures were characterized as isorhamnetin 3-glucosyl(1----3)galactoside, isorhamnetin 3-[6'acetylglucosyl(1----3)galactoside], isorhamnetin 3-[4'6'-di-acetylglucosyl(1----3)galactoside], and syringetin 3-[6'-acetylglucosyl(1----3)galactoside], respectively. In the aerial parts of the plant, seven known compounds were also confirmed.     

Antioxidant properties of flavonol glycosides from tea

We have determined the antioxidant activity of the major flavonols found in tea: a monoglycoside, a diglycoside and two triglycosides of kaempferol and three monoglycosides, a diglycoside and two triglycosides of quercetin. The Trolox equivalent antioxidant capacity (TEAC) and inhibition of iron/ascorbate-induced lipid peroxidation of phosphatidyl choline vesicles were measured. In the aqueous phase TEAC assay, the quercetin monoglycosides and diglycoside were approximately half as effective as quercetin aglycone. The quercetin triglycosides were much less effective than the monoglycosides and the diglycoside. The kaempferol glycosides were 32-39% less effective in the aqueous phase antioxidant assay compared to the kaempferol aglycone. Quercetin monoglycosides and diglycoside were potent inhibitors of lipid peroxidation, in contrast to the triglycoside which was much less effective. All the kaempferol glycosides were significantly less potent inhibitors of lipid peroxidation compared to the kaempferol aglycone. The compounds described herein demonstrate the antioxidant activity of the major flavonols in tea and indicate the effect of substituting a range of sugar moieties in the phenolic C ring.