Features in the NMR spectra of the aglycones of Agave spp. saponins. HMBC method for aglycone identification (HMAI)

Introduction: The analysis and detection of steroidal saponins is mainly performed using chromatographic techniques coupled with mass spectrometry. However, nuclear magnetic resonance (NMR) spectroscopy is a potential tool that can be combined with these techniques to obtain unambiguous structural characterisation. Objective: This work provides a review of the carbon-13 (13C)- and proton (1H)-NMR spectroscopic data of aglycones from Agave saponins reported in the literature and also the development of an easy identification method for these natural products. Methods: The database Scifinder was used for spectroscopic data collection in addition to data obtained from the Cadiz Allelopathy research group. The keywords used were Agave, spirostanic, furostanic, and saponin. Results: The shielding variations produced by functional groups on the aglycone core and the structural features of the most representative aglycones from Agave species are described. The effects are additive for up to four long-range connectivities. A method for the identification of aglycones (HMAI) is proposed to classify aglycones from Agave spp. through the use of 1H-NMR and heteronuclear multiple bond correlation (HMBC) experiments. Conclusions: The HMBC spectrum is representative of the structural features of aglycones from Agave spp. The HMBC method for aglycone identification (HMAI) method allowed the identification of pure saponins or mixtures thereof and this method can be used in combination with chromatographic techniques coupled with mass spectrometry to provide a more thorough analysis of Agave samples that contain aglycones

Isolation and Structural Determination of Triterpenoid Glycosides from the Aerial Parts of Alsike Clover (Trifolium hybridum L.)

Five azukisapogenol glycosides (1−5) have been isolated from the aerial parts of alsike clover (Trifolium hybridum L.), and their structures were elucidated by combined spectroscopic, spectrometric (1D and 2D NMR; HRESIMS, ESI−MS/MS), and chemical methods. Three of them are new compounds and were identified as 3-O-[-α-L-arabinopyranosyl(1→2)]-β-Dglucuronopyranosyl azukisapogenol (1), 3-O-[-β-D-glucuronopyranosyl(1→2)-β-D-glucuronopyranosyl]-29-O-β-D-glucopyranosyl azukisapogenol (2), and 3-O-[-α-L-arabinopyranosyl(1→2)-β-D-glucuronopyranosyl]-29-O-β-D-glucopyranosyl azukisapogenol (3). The remaining two (4, 5) are known compounds but have not been previously described as saponins constituents of the genus Trifolium. Also, azukisapogenol is reported here as a triterpenoid aglycone for the first time in this genus. Finally, the main chemotaxonomic features that may be recognized as specific of Trifolium species were discussed

Steroidal Saponins from Furcraea hexapetala Leaves and Their Phytotoxic Activity

Four new steroidal saponins (1−4) along with 13 known saponins were isolated from the leaves of Furcraea hexapetala. The new compounds were identified as (20R,22R,25R)-3β-hydroxy-5α-spirostan-12-one 3-O-{α-Lrhamnopyranosyl-(1→4)-O-β-D-glucopyranosyl-(1→3)-O-[β-D-glucopyranosyl-(1→3)-O-β-D-glucopyranosyl-(1→2)]-O-β-D-glucopyranosyl-(1→4)-O-β-D-galactopyranoside} (1), (25R)-3β-hydroxy-5α-spirost-20(21)-en-12-one 3-O-{α-Lrhamnopyranosyl-(1→4)-O-β-D-glucopyranosyl-(1→3)-O-[β-D-glucopyranosyl-(1→3)-O-β-D-glucopyranosyl-(1→2)]-O-β-D-glucopyranosyl-(1→4)-O-β-D-galactopyranoside} (2), (25R)-5α-spirostan-3β-ol 3-O-{β-D-glucopyranosyl-(1→2)-O-β-D-glucopyranosyl-(1→2)-O-β-D-glucopyranosyl-(1→4)-O-β-D-galactopyranoside} (3), and (25R)-5β-spirostan-3β-ol 3-O-{β-D-glucopyranosyl-(1→6)-O-β-D-galactopyranoside} (4) by spectroscopic analysis, including one- and two-dimensional NMR techniques, mass spectrometry, and chemical methods. The phytotoxicity of the isolated compounds against the standard target species Lactuca sativa was evaluated. Structure−activity relationships for these compounds with respect to phytotoxic effects are discussed

Bioactive steroidal saponins from Agave offoyana flowers

Bioguided studies of flowers of Agave offoyana allowed the isolation of five steroidal saponins never described previously, Magueyosides A–E (1–5), along with six known steroidal saponins (6–11). The structures of compounds were determined as (25R)-spirost-5-en-2a,3b-diol-12-one 3-O-{b-D-xylopyranosyl-(1-3)-O-b-D-glucopyranosyl-(1-2)-O-[b-D-xylopyranosyl-(1-3)]-O-b-D-glucopyranosyl-( 1-4)-O-b-D-galactopyranoside} (1), (25R)-spirost-5-en-2a,3b-diol-12-one 3-O-{b-D-glucopyranosyl-(1-2)-O-[b-D-xylopyranosyl-(1-3)]-O-b-D-glucopyranosyl-(1-4)-O-b-D galactopyranoside} (2), (25R)-spirost-5-en-2a,3b,12b-triol 3-O-{b-D-glucopyranosyl-(1-2)-O-[b-D-xylopyranosyl-(1-3)]- O-b-D-glucopyranosyl-(1-4)-O-b-D-galactopyranoside} (3), (25R)-5a-spirostan-2a,3b-diol-12-one 3-O-{b-D-xylopyranosyl-(1-3)-O-b-D-glucopyranosyl-(1-2)-O-[b-D-xylopyranosyl-(1-3)]-O-b-D-glucopyranosyl-(1-4)-O-b-D-galactopyranoside} (4), and (25R)-5a-spirostan-2a,3b-diol-9(11)-en-12-one 3-O-{b-D-xylopyranosyl-(1-3)-O-b-D-glucopyranosyl-(1-2)-O-[b-D-xylopyranosyl-(1-3)]-O-b-D-glucopyranosyl-( 1-4)-O-b-D-galactopyranoside} (5), by comprehensive spectroscopic analysis, including one- and two-dimensional NMR techniques, mass spectrometry and chemical methods. The bioactivities of the isolated compounds on the standard target species Lactuca sativa were evaluated. A dosedependent phytotoxicity and low dose stimulation were observed

Is eating raisins healthy?

Raisins are dried grapes consumed worldwide that contain beneficial components for human health. They are rich in fiber and phytochemicals such as phenolic compounds. Despite a 60% sugar content, several studies have reported health-promoting properties for raisins and this review compiles the intervention studies, as well as the cell line and animal model studies carried out to date. It has been demonstrated that raisins possess a low-to-moderate glycemic index, which makes them a healthy snack. They seem to contribute to a better diet quality and may reduce appetite. Their antioxidant capacity has been correlated to the phenolic content and this may be involved in the improvement of cardiovascular health. In addition, raisins maintain a good oral health due to their antibacterial activity, low adherence to teeth and an optimum oral pH. Raisin consumption also seems to be favorable for colon function, although more studies should be done to conclude this benefit. Moreover, gut microbiota could be affected by the prebiotic content of raisins. Cell line and animal model studies show other potential benefits in specific diseases, such as cancer and Alzheimer's disease. However, deeper research is required and future intervention studies with humans are needed. Overall, incorporating an 80-90 g portion of raisins (half a cup) into the daily diet may be favorable for human health

Phytotoxic steroidal saponins from Agave offoyana leaves

A bioassay-guided fractionation of Agave offoyana leaves led to the isolation of five steroidal saponins (1–5) along with six known saponins (6–11). The compounds were identified as (25R)-spirost-5-en-2α,3β-diol-12-one 3-O-{α-L-rhamnopyranosyl-(1→3)-O-β-D-glucopyranosyl-(1→2)-O-[β-D-xylopyranosyl-(1→3)]-O-β-D-glucopyranosyl-(1→4)-O-β-D-galactopyranoside} (1), (25R)-spirost-5-en-3β-ol-12-one 3-O-{α-L-rhamnopyranosyl-(1→3)-O-β-D-glucopyranosyl-(1→2)-O-[β-D-xylopyranosyl-(1→3)]-O-β-D-glu copyranosyl-(1→4)-O-β-D-galactopyranoside} (2), (25R)-spirost-5-en-3β-ol-12-one 3-O-{β-D-xylopyrano syl-(1→3)-O-β-D-glucopyranosyl-(1→2)-O-[β-D-xylopyranosyl-(1→3)]-O-β-D-glucopyranosyl-(1→4)-O-β -D-galactopyranoside} (3), (25R)-26-O-β-D-glucopyranosylfurost-5-en-3β,22α,26-triol-12-one 3-O- {α-L-rhamnopyranosyl-(1→3)-O-β-D-glucopyranosyl-(1→2)-O-[β-D-xylopyranosyl-(1→3)]-O-β-D-glucopyrano syl-(1→4)-O-β-D-galactopyranoside} (4) and (25R)-26-O-β-D-glucopyranosylfurost-5-en-3β,22α,26-triol- 12-one 3-O-{β-D-xylopyranosyl-(1→3)-O-β-D-glucopyranosyl-(1→2)-O-[β-D-xylopyranosyl-(1→3)]-O-β- D-glucopyranosyl-(1→4)-O-β-D-galactopyranoside} (5) by comprehensive spectroscopic analysis, including one- and two-dimensional NMR techniques, mass spectrometry and chemical methods. The phytotoxicity of the isolated compounds on the standard target species Lactuca sativa was evaluated

Triterpenoid saponins from the aerial parts of Trifolium argutum Sol. and their phytotoxic evaluation

Four triterpenoid saponins (1–4) were isolated from the aerial parts of Trifolium argutum Sol. (sharptooth clover) and their structures were elucidated by comprehensive spectroscopic analysis, including 1D and 2D NMR techniques, mass spectrometry and chemical methods. Two of them are new compounds, characterized as 3-O-[α-L-rhamnopyranosyl-(1→2)-β-D-galactopyranosyl-(1→2)-β-D-glucuronopyra- nosyl]-3β,24-dihydroxyolean-12-ene-22-oxo-29-oic acid (1) and 3-O-[β-D-galactopyranosyl-(1→2)- β-D-glucuronopyranosyl]-3β,24-dihydroxyolean-12-ene-22-oxo-29-oic acid (2). The occurrence of 3β,24-dihydroxyolean-12-ene-22-oxo-29-oic acid (melilotigenin) in its natural form is reported for the first time as a triterpenoid aglycone within Trifolium species. The phytotoxicity of compounds was evaluated on four STS at concentration 1 μM to 333 mM. Compound 1 was the most active, showing more than 60% inhibition on the root growth of L. sativa at the higher dose, with IC50 (254.1 μM) lower than that of Logran1 (492.6 μM), a commercial herbicide used as positive control. The structure–activity relationships indicated that both aglycones and glycosidic parts may influence the phytotoxicity of saponins

Phenolic Profile of Grape Canes: Novel Compounds Identified by LC-ESI-LTQ-Orbitrap-MS

Grape canes (Vitis vinifera L.) are a viticulture industry by-product with an important content of secondary metabolites, mainly polyphenols with a broad spectrum of demonstrated health benefits. Grape canes, therefore, have considerable economic potential as a source of high-value phytochemicals. In this work, liquid chromatography coupled with electrospray ionization hybrid linear trap quadrupole-Orbitrap mass spectrometry (LC-LTQ-Orbitrap) was used for the comprehensive identification of polyphenolic compounds in grape canes. Identification of polyphenols was performed by comparing their retention times, accurate mass measured, and mass fragmentation patterns with those of reference substances or available data in the literature. A total of 75 compounds were identified, including phenolic acids, flavanols, flavonols, flavanonols, flavanones, and stilbenoids. The most abundant polyphenols were proanthocyanidins and stilbenoids and their oligomers. Moreover, the high-resolution mass spectrometry analysis revealed the occurrence of 17 polyphenols never described before in grape canes, thereby providing a more complete polyphenolic profile of this potentially valuable by-product

Adipocyte-specific protein tyrosine phosphatase 1B deletion increases lipogenesis, adipocyte cell size and is a minor regulator of glucose homeostasis

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Seed storage conditions change the germination pattern of clonal growth plants in Mediterranean salt marshes.

8 páginas, 4 tablas, 8 figuras.The effect of salinity level and extended exposure to different salinity and flooding conditions on germination patterns of three saltmarsh clonal growth plants (Juncus subulatus, Scirpus litoralis, and S. maritimus) was studied. Seed exposure to extended flooding and saline conditions significantly affected the outcome of the germination process in a different, though predictable, way for each species, after favorable conditions for germination were restored. Tolerance of the germination process was related to the average salinity level measured during the growth/germination season at sites where established individuals of each species dominated the species cover. No relationship was found between salinity tolerance of the germination process and seed response to extended exposure to flooding and salinity conditions. The salinity response was significantly related to the conditions prevailing in the habitats of the respective species during the unfavorable (nongrowth/nongermination) season. Our results indicate that changes in salinity and hydrology while seeds are dormant affect the outcome of the seed-bank response, even when conditions at germination are identical. Because these environmental-history-dependent responses differentially affect seed germination, seedling density, and probably sexual recruitment in the studied and related species, these influences should be considered for wetland restoration and managementFinancial support from the Spanish Ministry of the Environment (MMA, project 05/99) and the Junta de Andalucía (research group 4086)enabled us to carry out the present work.Peer reviewe