Separation, Identification, and Bioactivities of the Main Gallotannins of Red Sword Bean (Canavalia gladiata) Coats

Hydrolyzable tannins are incorporated into the endocarp during sclerification of the water caltrop Trapa natans

The water caltrop (Trapa natans) develops unique woody fruits with unusually large seeds among aquatic plants. During fruit development, the inner fruit wall (endocarp) sclerifies and forms a protective layer for the seed. Endocarp sclerification also occurs in many land plants with large seeds; however, in T. natans, the processes of fruit formation, endocarp hardening, and seed storage take place entirely underwater. To identify potential chemical and structural adaptations for the aquatic environment, we investigated the cell-wall composition in the endocarp at a young developmental stage, as well as at fruit maturity. Our work shows that hydrolyzable tannins-specifically gallotannins-flood the endocarp tissue during secondary wall formation and are integrated into cell walls along with lignin during maturation. Within the secondary walls of mature tissue, we identified unusually strong spectroscopic features of ester linkages, suggesting that the gallotannins and their derivatives are cross-linked to other wall components via ester bonds, leading to unique cell-wall properties. The synthesis of large amounts of water-soluble, defensive aromatic metabolites during secondary wall formation might be a fast way to defend seeds within the insufficiently lignified endocarp of T. natans.

Separation of Antioxidant-Rich Alternanthera Sessilis Red Extracts by Sephadex LH-20 and Identification of Polyphenols Using HPLC-QToF-MS/MS

This study aimed to fractionate Alternanthera sessilis Red (ASR) crude extracts and determine their antioxidant activities as well as the related active components in the whole plant. ASR was extracted with water and ethanol, and further separated using a Sephadex LH-20 column. Following the assessments of the polyphenolic contents and antioxidant activities of crude extracts (H2 OASR and EtOHASR ) and fractions, a HPLC-QToF analysis was performed on the crude extracts and selected fractions (H2 OASR FII and EtOHASR FII). Three water fractions (H2 OASR FI, FII and FIII) and four ethanolic fractions (EtOHASR FI, FII, FIII and FIV) were derived from their crude extracts, respectively. EtOHASR FII exhibited the greatest total phenolic content (120.41 mg GAE/g fraction), total flavonoid content (223.07 mg RE/g fraction), and antioxidant activities (DPPH IC50 =159.43 μg/mL; FRAP=1.93 mmol Fe2+ /g fraction; TEAC=0.90 mmol TE/g fraction). Correlation analysis showed significant (p<0.01) positive correlations between both TPC (r=0.748-0.970) and TFC (r=0.686-0.949) with antioxidant activities in the crude extracts and fractions. Flavonoids were the major compounds in the four selected samples tentatively identified using HPLC-QToF-MS/MS, with the highest number of 30 polyphenol compounds detected in the most active fraction, EtOHASR FII.

Inhibition Effect of Adipogenesis and Lipogenesis via Activation of AMPK in Preadipocytes Treated with Canavalia gladiata Extract

The aim of this study was to investigate the effect of Canavalia gladiata extract (CGE) on the regulation of AMP-activated protein kinase (AMPK) in 3T3-L1 preadipocytes and evaluate the adipogenesis and lipogenesis mechanisms. In 3T3-L1 preadipocytes, lipid accumulation and differentiation were suppressed by 1.1, 1.3, and 1.4 times under the CGE treatment at 0.25, 0.5, and 1.0 mg/mL, respectively. The expression of the main genes involved in the inhibition of adipogenesis was evaluated at the mRNA level via a transcription-polymerase chain reaction. The extract at 1.0 mg/mL increased the mRNA expressions of AMPK and carnitine palmitoyl transferase-1 (CPT-1) by 1.9 and 1.2 times, respectively, while it decreased the expression of sterol regulatory element binding proteins-1c (SREBP-1c), peroxisome proliferator activated receptor-γ (PPAR-γ), CCAAT enhancer binding protein-α (C/EBP-α), and fatty acid synthase (FAS) by 1.1, 1.2, 1.8, and 1.5 times, respectively, indicating inhibition of the adipogenesis and lipogenesis potential of CGE. Gallic acid (4.02 mg/g) was identified as the main component of the CGE via LC-MS/MS and HPLC analysis. The results of this study suggested that CGE can be utilized as an anti-obesity food additive or medication by activating the AMPK-induced regulation and suppressing adipogenesis transcription factors.

Selectivity Tuning by Natural Deep Eutectic Solvents (NADESs) for Extraction of Bioactive Compounds from Cytinus hypocistis—Studies of Antioxidative, Enzyme-Inhibitive Properties and LC-MS Profiles

In the present study, the extracts of Cytinus hypocistis (L.) L using both traditional solvents (hexane, ethyl acetate, dichloromethane, ethanol, ethanol/water, and water) and natural deep eutectic solvents (NADESs) were investigated in terms of their total polyphenolic contents and antioxidant and enzyme-inhibitive properties. The extracts were found to possess total phenolic and total flavonoid contents in the ranges of 26.47–186.13 mg GAE/g and 0.68–12.55 mg RE/g, respectively. Higher total phenolic contents were obtained for NADES extracts. Compositional differences were reported in relation to antioxidant potential studied by several assays (DPPH: 70.19–939.35 mg TE/g, ABTS: 172.56–4026.50 mg TE/g; CUPRAC: 97.41–1730.38 mg TE/g, FRAP: 84.11–1534.85 mg TE/g). Application of NADESs (choline chloride—urea 1:2, a so-called Reline) allowed one to obtain the highest number of extracts having antioxidant potential in the radical scavenging and reducing assays. NADES-B (protonated by HCl L-proline-xylitol 5:1) was the only extractant from the studied solvents that isolated a specific fraction without chelating activity. Reline extract exhibited the highest acetylcholinesterase inhibition compared to NADES-B and NADES-C (protonated by H2SO4 L-proline-xylitol 5:1) extracts, which showed no inhibition. The NADES extracts were observed to have higher tyrosinase inhibitory properties compared to extracts obtained by traditional organic solvents. Furthermore, the NADES extracts were relatively better inhibitors of the diabetic enzymes. These findings provided an interesting comparison in terms of total polyphenolic content yields, antioxidant and enzyme inhibitory properties (cholinesterase, amylase, glucosidase, and tyrosinase) between traditional solvent extracts and NADES extracts, used as an alternative. While the organic solvents showed better antioxidant activity, the NADES extracts were found to have some other improved properties, such as higher total phenolic content and enzyme-inhibiting properties, suggesting functional prospects for their use in phytonutrient extraction and fractionation. The obtained results could also be used to give a broad overview of the different biological potentials of C. hypocistis.

In vitro metabolic biomodulation of irinotecan to increase potency and reduce dose-limiting toxicity by inhibition of SN-38 glucuronide formation

OBJECTIVES

Colorectal cancer continues to have one of the highest incidents of occurrence with a rising rate of diagnosis among people under the age of 50. Chemotherapy with irinotecan results in severe gastrointestinal dose-limiting toxicity that is caused by the glucuronidated form of the active metabolite (SN-38G). This study evaluates herbal compounds and analogs to biomodulate the metabolism of IR to decrease dose-limiting toxicity while increasing the amount of the active metabolite.

METHODS

In vitro metabolism using human liver microsomes was conducted with white willow bark (WWB) extract, select specific components of WWB, and analogues to evaluate biomodulation of the IR metabolism. Samples were analyzed using liquid chromatography-tandem mass spectrometry to measure metabolites between reactions with and without herbals components.

RESULTS

WWB showed an optimal decrease (>80%) in SN-38G and a corresponding increase in SN-38 levels (128%) at a concentration of near 200 μg/mL. Tannic acid produced a 75% decrease in SN-38G with a 130% increase in SN-38 at 10 μg/mL, whereas the treatment with beta-pentagalloyl glucose and various analogues decreased SN-38G by 70% and increased SN-38 by 20% at 10 μg/mL.

CONCLUSIONS

These results suggest naturally occurring compounds from WWB may have the potential to increase potency by increasing the conversion of IR to SN-38 and decrease dose-limiting toxicity of IR chemotherapy by reducing glucuronidation of SN-38.

Recognition of Gallotannins and the Physiological Activities: From Chemical View

Gallotannins, characterized with the glycosidic core and galloyl unit, are seemed as vital components of hydrolyzable tannins. Benefit from the more and more discoveries of their bioactivities and edibility, application of gallotannins in food industry, pharmacy industry, and other fields is increasing. Inheriting previous study achievements, chemical structure of gallotannins was illustrated and degradation as well as synthetic routes to gallotannins were summarized. On this basis, distribution in the nature also including the distinction of gallotannins was discussed. More than that, activities involving in antioxidant, anti-inflammatory, enzyme inhibitions, protein binding, and so on, as well as applications in the field of food industry, biopharmaceutical science, agricultural production, etc., were combed. Finally, improvement of bioavailability, chemical modification of the structure, and accurate determination of new gallotannins were pointed out to be the orientation in the future.

Ellagic Acid: A Review on Its Natural Sources, Chemical Stability, and Therapeutic Potential

Ellagic acid (EA) is a bioactive polyphenolic compound naturally occurring as secondary metabolite in many plant taxa. EA content is considerable in pomegranate (Punica granatum L.) and in wood and bark of some tree species. Structurally, EA is a dilactone of hexahydroxydiphenic acid (HHDP), a dimeric gallic acid derivative, produced mainly by hydrolysis of ellagitannins, a widely distributed group of secondary metabolites. EA is attracting attention due to its antioxidant, anti-inflammatory, antimutagenic, and antiproliferative properties. EA displayed pharmacological effects in various in vitro and in vivo model systems. Furthermore, EA has also been well documented for its antiallergic, antiatherosclerotic, cardioprotective, hepatoprotective, nephroprotective, and neuroprotective properties. This review reports on the health-promoting effects of EA, along with possible mechanisms of its action in maintaining the health status, by summarizing the literature related to the therapeutic potential of this polyphenolic in the treatment of several human diseases.

Roasting and Cryogenic Grinding Enhance the Antioxidant Property of Sword Beans (Canavalia gladiata)

The objective of this study was to optimize the conditions for enhancing the antioxidant properties of sword bean (Canavalia gladiata) as a coffee substitute in two processing methods, roasting and grinding. The optimum conditions for removing off-flavor of the bean and maximizing functionality and efficiency were light roasting and cryogenic grinding (< 53 μm). In these conditions, extraction yield was 16.75%, total phenolic content (TPC) was 69.82 ± 0.35 mg gallic acid equivalents/g, and total flavonoid content (TFC) was 168.81 ± 1.64 mg quercetin equivalents/100 g. The antioxidant properties were 77.58 ± 0.27% for DPPH radical scavenging activity and 58.02 ± 0.76 mg Trolox equivalents/g for ABTS radical scavenging activity. The values for TFC and ABTS radical scavenging activity were significantly higher (p < 0.05) than in other conditions, and TPC and DPPH radical scavenging activity were second highest in lightly roasted beans, following raw beans. HS-SPME/GCMS analysis confirmed that the amino acids and carbohydrates, which are the main components of sword bean, were condensed into other volatile flavor compounds, such as derivatives of furan, pyrazine, and pyrrole during roasting. Roasted and cryogenically ground (cryo-ground) sword beans showed higher functionality in terms of TFC, DPPH, and ABTS radical scavenging activities compared to those of coffee. Overall results showed that light roasting and cryogenic grinding are the most suitable processing conditions for enhancing the bioactivity of sword beans.

Antimicrobial Capacity of Plant Polyphenols against Gram-positive Bacteria: A Comprehensive Review

BACKGROUND

Multi-drug-resistant bacteria such as Methicillin-Resistant Staphylococcus aureus (MRSA) disseminate rapidly amongst patients in healthcare facilities and suppose an increasingly important cause of community-associated infections and associated mortality. The development of effective therapeutic options against resistant bacteria is a public health priority. Plant polyphenols are structurally diverse compounds that have been used for centuries for medicinal purposes, including infections treatment and possess, not only antimicrobial activity, but also antioxidant, anti-inflammatory and anticancer activities among others. Based on the existing evidence on the polyphenols' antibacterial capacity, polyphenols may be postulated as an alternative or complementary therapy for infectious diseases.

OBJECTIVE

To review the antimicrobial activity of plant polyphenols against Gram-positive bacteria, especially against S. aureus and its resistant strains. Determine the main bacterial molecular targets of polyphenols and their potential mechanism of action.

METHODOLOGY

The most relevant reports on plant polyphenols' antibacterial activity and their putative molecular targets were studied. We also performed virtual screening of thousand different polyphenols against proteins involved in the peptidoglycan biosynthesis to find potential valuable bioactive compounds. The bibliographic information used in this review was obtained from MEDLINE via PubMed.

RESULTS

Several polyphenols: phenolic acids, flavonoids (especially flavonols), tannins, lignans, stilbenes and combinations of these in botanical mixtures, have exhibited significant antibacterial activity against resistant and non-resistant Gram-positive bacteria at low μg/mL range MIC values. Their mechanism of action is quite diverse, targeting cell wall, lipid membrane, membrane receptors and ion channels, bacteria metabolites and biofilm formation. Synergic effects were also demonstrated for some combinations of polyphenols and antibiotics.

CONCLUSION

Plant polyphenols mean a promising source of antibacterial agents, either alone or in combination with existing antibiotics, for the development of new antibiotic therapies.

New caryophyllene-type sesquiterpene and flavonol tetraglycoside with sixteen known compounds from sword bean (Canavalia gladiata)

Eighteen compounds including new caryophyllene-type sesquiterpene and flavonol tetraglycoside were purified and isolated from sword beans (Canavalia gladiata). Two new compounds, (Z,1R,7S,9S)-7-hydroxy-11,11-dimethyl-8-methylenebicyclo[7.2.0]undec-4-ene-4-carboxylic acid (2) and kaempferol-7-O-α-l-dirhamnopyranosyl(1 → 2;1 → 6)-O-β-d-glucopyranosyl(1 → 2)-O-α-l-rhamnopyranoside (9), were identified. Other known compounds including methyl gallate (1), (2S,3S,4E,8E)-2-aminooctadeca-4,8-diene-1,3-diol 1-O-β-d-glucopyranoside (3), (2S,3S,4E,8Z)-2-aminooctadeca-4,8-diene-1,3-diol 1-O-β-d-glucopyranoside (4), lupeol (5), trilinolein (6), 1,6-di-O-galloyl β-d-glucopyranoside (7), N-(2-methoxybenzoyl)homoserine (8), dihydrophaseic acid (10), dillenetin (11), kaempferol-7-O-[2-O-β-d-glucopyranosyl-6-O-α-l-rhamnopyranosyl]-α-l-rhamnopyranoside (12), canavalioside (13), kaempferol-3-O-[2-O-β-d-glucopyranosyl-6-O-α-l-rhamnopyranosyl]-β-d-glucopyranoside (14), kaempferol-3-O-(2,6-O-α-l-dirhamnopyranosyl)-β-d-glucopyranoside (15), kaempferol-3-O-rutinoside (16), gladiatoside A₁ (17), and gladiatoside B₁ (18) were identified. The chemical structures of these compounds were determined by ESI-MS and NMR analyses.

Edible Sword Bean Extract Induces Apoptosis in Cancer Cells In Vitro and Inhibits Ascites and Solid Tumor Development In Vivo

Antitumor potential of edible sword bean (Canavalia gladiata (L.)) extract has been evaluated against Daltons lymphoma ascites (DLA) using in vitro and in vivo studies. Methanolic extraction was carried out and in vitro studies were performed against both DLA and A549, lung cancer cell lines. The results revealed that sword bean extract inhibited cell growth and induced apoptosis as evidenced by cytotoxic assay, Hoechst 33342 staining and acridine orange/ethidium bromide dual staining. In vivo studies performed on DLA induced solid as well as ascitic tumors models showed administration of sword bean extract (10 mg/kg B.wt.) could significantly inhibit ascitic and solid tumor development in mice. Therefore, our overall results revealed that C. gladiata treatment could significantly inhibit tumor development and induce apoptosis in tumor cells.

Interaction of polyphenols with model membranes: Putative implications to mouthfeel perception

Food polyphenols in fruits juices, tea, coffee, wine and beer confer sensory properties such as colour, astringency and bitterness. The development of functional healthy drinks without the unpleasant sensory feeling is boosting research for a clearer understanding on the interactions of polyphenols within the oral mucosa. In this study we investigated the interaction of astringent polyphenols, namely ECG, EGCG, procyanidin B4 and PGG, with lipids in model membranes by spectroscopic techniques. The membrane model was built varying the cholesterol content to mimic mouth regions and experiments were conducted at pH 5 to mimic the pH drop at the moment of beverage (e.g. green tea, red wine) intake. Fluorescence quenching results conducted on LUVs with cholesterol molar fractions ranging between 0.34 < χ_chol < 0.74 and similar size distributions (122.9 ± 3.7 nm) showed that interaction of polyphenols is structure- and concentration-dependent. Also, the decrease of partition constants (K_p) with increasing cholesterol content (χchol) suggest that the affinity of polyphenols is weaker in cholesterol-rich liposomes. STD results revealed that the interaction of EGCG and PGG with membrane lipids involved mainly galloyl residues. Overall, spectroscopic data show that polyphenols interact to higher extent with more polar regions found in buccal, flour of the mouth and gingiva regions than with more hydrophobic regions located in the palate and tongue supporting that lipid microenvironments play a role in oral sensory perception.