Oligosaccharides and Complex Carbohydrates: A New Paradigm for Cranberry Bioactivity.

Cranberry is a well-known functional food, but the compounds directly responsible for many of its reported health benefits remain unidentified. Complex carbohydrates, specifically xyloglucan and pectic oligosaccharides, are the newest recognized class of biologically active compounds identified in cranberry materials. Cranberry oligosaccharides have shown similar biological properties as other dietary oligosaccharides, including effects on bacterial adhesion, biofilm formation, and microbial growth. Immunomodulatory and anti-inflammatory activity has also been observed. Oligosaccharides may therefore be significant contributors to many of the health benefits associated with cranberry products. Soluble oligosaccharides are present at relatively high concentrations (~20% w/w or greater) in many cranberry materials, and yet their possible contributions to biological activity have remained unrecognized. This is partly due to the inherent difficulty of detecting these compounds without intentionally seeking them. Inconsistencies in product descriptions and terminology have led to additional confusion regarding cranberry product composition and the possible presence of oligosaccharides. This review will present our current understanding of cranberry oligosaccharides and will discuss their occurrence, structures, ADME, biological properties, and possible prebiotic effects for both gut and urinary tract microbiota. Our hope is that future investigators will consider these compounds as possible significant contributors to the observed biological effects of cranberry.

Arabinoxyloglucan Oligosaccharides May Contribute to the Antiadhesive Properties of Porcine Urine after Cranberry Consumption.

Cranberry ( Vaccinium macrocarpon) juice is traditionally used for the prevention of urinary tract infections. Human urine produced after cranberry juice consumption can prevent Escherichia coli adhesion, but the antiadhesive urinary metabolites responsible have not been conclusively identified. Adult female sows were therefore fed spray-dried cranberry powder (5 g/kg/day), and urine was collected via catheter. Urine fractions were tested for antiadhesion activity using a human red blood cell (A+) anti-hemagglutination assay with uropathogenic P-fimbriated E. coli. Components were isolated from fractions of interest using Sephadex LH-20 gel filtration chromatography followed by HPLC on normal and reversed-phase sorbents with evaporative light scattering detection. Active urine fractions were found to contain a complex series of oligosaccharides but not proanthocyanidins, and a single representative arabinoxyloglucan octasaccharide was isolated in sufficient quantity and purity for full structural characterization by chemical derivatization and NMR spectroscopic methods. Analogous cranberry material contained a similar complex series of arabinoxyloglucan oligosaccharides that exhibited antiadhesion properties in preliminary testing. These results indicate that oligosaccharides structurally related to those found in cranberry may contribute to the antiadhesion properties of urine after cranberry consumption.

Structural Characterization of Cranberry Arabinoxyloglucan Oligosaccharides.

Cranberry ( Vaccinium macrocarpon) products are widely available in North American food, juice, and dietary supplement markets. The use of cranberry is popular for the prevention of urinary tract infections (UTIs) and other reported health benefits. Preliminary findings by our research group indicate that arabinoxyloglucan oligosaccharides are present in cranberry products and may contribute to the antiadhesion properties of urine produced after cranberry consumption, but relatively little is known regarding the oligosaccharide components of cranberry. This report describes the isolation from two cranberry sources and the complete structure elucidation of two arabinoxyloglucan oligosaccharides through the use of carbohydrate-specific NMR spectroscopic and chemical derivatization methods. These compounds were identified as the heptasaccharide ß-d-glucopyranosyl-(1→4)-[α-d-xylopyranosyl-(1→6)]-ß-d-glucopyranosyl-(1→4)-ß-d-glucopyranosyl-(1→4)-[α-l-arabinofuranosyl-(1→2)-α-d-xylopyranosyl-(1→6)]-ß-d-glucopyranose (1) and the octasaccharide ß-d-glucopyranosyl-(1→4)-[α-l-arabinofuranosyl-(1→2)-α-d-xylopyranosyl-(1→6)]-ß-d-glucopyranosyl-(1→4)-ß-d-glucopyranosyl-(1→4)-[α-l-arabinofuranosyl-(1→2)-α-d-xylopyranosyl-(1→6)]-ß-d-glucopyranose (2). Selected fractions and the isolated compounds were subjected to antimicrobial, cell viability, and E. coli antiadhesion assays. Results indicated that enriched fractions and purified compounds lacked antimicrobial and cytotoxic effects, supporting the potential use of such compounds for disease prevention without the risk for resistance development. Preliminary antiadhesion results indicated that mixtures of oligosaccharides exhibited greater antiadhesion properties than purified fractions or pure compounds. The potential use of cranberry oligosaccharides for the prevention of UTIs warrants continued investigations of this complex compound series.

Mansoins C-F, Oligomeric Flavonoid Glucosides Isolated from Mansoa hirsuta Fruits with Potential Anti-inflammatory Activity.

Continued investigation of the polyphenolic pool of the fruits of Mansoa hirsuta afforded four additional members of the new class of glucosylated oligomeric flavonoids comprising a flavanone core linked to 1,3-diarylpropane C6-C3-C6 units. The structures and absolute configurations of mansoins C-F (3-6) were established by analysis of NMR and electronic circular dichroism data. Mansoin C (3) was identified as a diglucosylated heterodimer, whereas mansoins D (4), E (5), and F (6) were identified as triglucosylated heterotrimers, isomeric with mansoin A (1). Mansoin F (6) inhibited TNF-α release by lipopolysaccharide-stimulated THP-1 cells (IC50 of 19.3 ± 1.3 µM) and, as with mansoin A (1), reduced the phosphorylation levels of p-65-NF-κB, when assayed at 50 µM. These results indicate that the potential anti-inflammatory properties of mansoin F (6) are probably due to inhibition of the NF-κB pathway and inhibition of TNF-α release.

Sulfated steroid-amino acid conjugates from the Irish marine sponge Polymastia boletiformis.

Antifungal bioactivity-guided fractionation of the organic extract of the sponge Polymastia boletiformis, collected from the west coast of Ireland, led to the isolation of two new sulfated steroid-amino acid conjugates (1 and 2). Extensive 1D and 2D NMR analyses in combination with quantum mechanical calculations of the electronic circular dichroism (ECD) spectra, optical rotation, and 13C chemical shifts were used to establish the chemical structures of 1 and 2. Both compounds exhibited moderate antifungal activity against Cladosporium cucumerinum, while compound 2 was also active against Candida albicans. Marine natural products containing steroidal and amino acid constituents are extremely rare in nature.

Antimicrobial and antiinsectan phenolic metabolites of Dalea searlsiae.

Continued interest in the chemistry of Dalea spp. led to investigation of Dalea searlsiae, a plant native to areas of the western United States. Methanol extractions of D. searlsiae roots and subsequent chromatographic fractionation afforded the new prenylated and geranylated flavanones malheurans A-D (1-4) and known flavanones (5 and 6). Known rotenoids (7 and 8) and isoflavones (9 and 10) were isolated from aerial portions. Structure determination of pure compounds was accomplished primarily by extensive 1D- and 2D-NMR spectroscopy. The absolute configurations of compounds 1-5, 7, and 8 were assigned using electronic circular dichroism spectroscopy. Antimicrobial bioassays revealed significant activity concentrated in the plant roots. Compounds 1-6 exhibited MICs of 2-8 µg/mL against Streptococcus mutans, Bacillus cereus, and oxacillin-sensitive and -resistant Staphylococcus aureus. Aerial metabolites 7-10 were inactive against these organisms, but the presence of 7 and 8 prompted investigation of the antiinsectan activity of D. searlsiae metabolites toward the major crop pest Spodoptera frugiperda (fall armyworm). While compounds 1-10 all caused significant reductions in larval growth rates, associated mortality (33-66%) was highest with flavanone 4 and rotenoids 7 and 8. These findings suggest a differential allocation of antimicrobial and antiinsectan plant resources to root and aerial portions of the plant, respectively.

TNF-α inhibition elicited by mansoins A and B, heterotrimeric flavonoids isolated from Mansoa hirsuta.

Mansoins A (1) and B (2) isolated from the fruits of Mansoa hirsuta represent new glucosylated heterotrimeric flavonoids with a flavanone core linked to two 1,3-diarylpropane C6-C3-C6 units. Their structures and absolute configurations were established by analysis of their NMR and electronic circular dichroism spectroscopic data. Compounds 1 and 2 inhibited TNF-α release by LPS-stimulated THP-1 cells with different potencies, with mansoin B (2) being active at lower concentrations than mansoin A (1) (IC50 values 20.0±1.4 and 48.1±1.8 µM, respectively). These results indicate potential anti-inflammatory properties for this structural type of oligoflavonoids, especially for mansoin B (2).

Pyrano-isoflavans from Glycyrrhiza uralensis with antibacterial activity against Streptococcus mutans and Porphyromonas gingivalis.

Continuing investigation of fractions from a supercritical fluid extract of Chinese licorice (Glycyrrhiza uralensis) roots has led to the isolation of 12 phenolic compounds, of which seven were described previously from this extract. In addition to these seven metabolites, four known components, 1-methoxyerythrabyssin II (4), 6,8-diprenylgenistein, gancaonin G (5), and isoglycyrol (6), and one new isoflavan, licorisoflavan C (7), were characterized from this material for the first time. Treatment of licoricidin (1) with palladium chloride afforded larger amounts of 7 and also yielded two new isoflavans, licorisoflavan D (8), which was subsequently detected in the licorice extract, and licorisoflavan E (9). Compounds 1-9 were evaluated for their antibacterial activities against the cariogenic Streptococcus mutans and the periodontopathogenic Porphyromonas gingivalis. Licoricidin (1), licorisoflavan A (2), and 7-9 showed antibacterial activity against P. gingivalis (MICs of 1.56-12.5 µg/mL). The most potent activity against S. mutans was obtained with 7 (MIC of 6.25 µg/mL), followed by 1 and 9 (MIC of 12.5 µg/mL). This study provides further evidence for the therapeutic potential of licorice extracts for the treatment and prevention of oral infections.

Fungal ABC transporter-associated activity of isoflavonoids from the root extract of Dalea formosa.

New potential treatments for disseminated fungal infections are needed, especially for infections caused by the commonly drug-resistant pathogens Candida albicans and C. glabrata. These pathogens cause systemic candidiasis, a significant cause of mortality in immune-compromised patients. ABC transporters of the pleiotropic drug resistance subfamily, such as Cdr1p of C. albicans, play an important role in antifungal resistance and are potential bioassay targets for antifungal therapies against drug-resistant pathogens. We observed strong antifungal growth inhibitory activity in the methanol extract of Dalea formosa roots. This extract afforded six new isoflavonoids, sedonans A-F (1-6), a new but-2-enolide, 4'-O-methylpuerol A (7), and the new pterocarpan ent-sandwicensin (8). The structures and absolute configurations of these compounds were assigned using spectroscopic and chiroptical techniques. The direct antifungal activity of 1 against C. glabrata (MIC = 20 µM) was higher than that of fluconazole. Sedonans A-F and ent-sandwicensin were also active against Saccharomyces cerevisiae strains that express differing ABC transporter-associated resistance mechanisms but differed in their susceptibility to Cdr1p-mediated detoxification. A sedonan A (1)/ent-sandwicensin (8) combination exhibited synergistic growth inhibition. The results demonstrate that multiple crude extract compounds are differentially affected by efflux-mediated resistance and are collectively responsible for the observed bioactivity.

Triterpenoids and flavonoids from Cecropia schreberiana Miq. (Urticaceae).

Phytochemical investigation of the leaves of Cecropia schreberiana Miq. (Urticaceae) led to the isolation of four triterpenoids (1-4), three flavone C-glycosides (5-7), two flavan-3-ols (8, 9), two flavanolignans (10, 11), and two proanthocyanidins (12, 13). All compounds were isolated from C. schreberiana for the first time. This is the first report demonstrating the presence of arjunolic acid (4), cinchonain Ia (10), and cinchonain Ib (11) in the Urticaceae family. The occurrence of flavanolignans within the family Urticaceae supports the likelihood that such compounds are more common within the class Magnoliopsida than previously thought.

Rapid isolation and identification of minor natural products by LC-MS, LC-SPE-NMR and ECD: isoflavanones, biflavanones and bisdihydrocoumarins from Ormocarpum kirkii.

The combination of the hyphenated techniques LC-MS and LC-SPE-NMR constitutes a powerful platform for the rapid isolation and identification of minor components from natural sources. Electronic circular dichroism (ECD) is a useful tool to determine the absolute configuration of small quantities of chiral molecules. In order to search for minor constituents present in an Ormocarpum kirkii extract, these techniques were applied for the separation and structure elucidation of a series of isoflavanones, biflavanones and biscoumarins. After optimization of chromatographic conditions and subsequent isolation, MS and 1D and 2D NMR data were collected. Experimental and calculated ECD spectra were used in conjunction with NMR data to confirm the absolute configuration of these compounds. Eight compounds were identified for the first time and six have been previously reported. The present approach offers a strategy for accelerating research on natural products.

Towards the synthesis of proanthocyanidins: half a century of innovation.

Results emanating from the synthesis of proanthocyanidins played a crucial role in defining the constitution, regiochemistry, and absolute configuration of this complex but fascinating group of plant secondary metabolites. The initial efforts, commencing in 1966, were focused on structure elucidation of, especially, the procyanidins, profisetinidins, and prorobinetinidins. However, over the past 12 years the emphasis has shifted to the synthesis of the bioactive procyanidins and some of their derivatives at a scale that would permit assessment of their pharmacological properties. With a few exceptions, the vast majority of these synthetic protocols involve the formation of the interflavanyl bond by acid/Lewis acid activation at C-4 of a flavan-3,4-diol or its equivalent, and subsequent trapping of the incipient C-4 carbocation by the nucleophilic centers of a flavan-3-ol (catechin). This review represents the first comprehensive chronicle depicting the development of the subject of proanthocyanidin synthesis.

Extending the elemental defense hypothesis: dietary metal concentrations below hyperaccumulator levels could harm herbivores.

Previous work has shown that hyperaccumulator levels of some metals can defend plants against herbivores, but the possibility of defense by metal concentrations at accumulator or normal levels is unexplored. This study tested the hypothesis that metals can defend plants at low concentrations. We determined the relative toxicities of eight metals commonly acquired by plants: Cd, Co, Cr, Cu, Mn, Ni, Pb, and Zn. Larvae of the diamondback moth (Plutella xylostella), a representative crucifer specialist, were fed with artificial diet amended with concentrations of metal varying from 2 to 3,000 microg/g. Different concentration ranges were used for each of the eight metals, and larval survival at 10-14 days was calculated for each concentration. All metals were toxic to diamondback moth larvae at hyperaccumulator levels. All metals, however, were also toxic to larvae at accumulator concentrations, far below those found in hyperaccumulating plants. Five metals (Cd, Mn, Ni, Pb, and Zn) were toxic below accumulator levels, Cd and Pb were toxic near the concentration ranges of normal plants, and Zn was toxic at a concentration within the normal range. Our results indicate that uptake of certain metals may provide a defensive benefit for plants, and that elemental defenses may be effective at concentrations far lower than previously hypothesized. This study implies that elemental defenses are more widespread in plants than previously believed, and that the ecological consequences of even low levels of metal accumulation need to be explored.