Insights from ß-Conglycinin and Glycinin into the Mechanism of Nanoliposome-Soybean Protein Isolate Interactions.

The interaction mechanism between nanoliposomes (NL) and a soybean protein isolate (SPI) was investigated via the complexation between NL and two major components of SPI, i.e., ß-conglycinin (7S) and glycinin (11S). The endogenous fluorescence emissions of 7S and 11S were statically quenched after complexation with NL, and the polarity of the SPI fluorophore increased. The interaction between NL and SPI was exothermic and spontaneous, 7S/11S secondary structures were altered, and more hydrophobic groups were exposed on protein surfaces. Moreover, the NL-SPI complex had a large zeta potential to attain system stability. Hydrophobic forces and hydrogen bonds played vital roles in the interaction between NL and 7S/11S, and a salt bridge was also involved in the NL-11S interaction. The binding characteristics between NL and 7S/11S were chiefly governed by the protein characteristics, such as amino acid composition, surface hydrophobicity, and advanced structure. These findings could deepen the understanding of the interaction mechanism between NL and SPI.

Mechanistic Understanding of Tyrosinase Inhibition by Polymeric Proanthocyanidins from Acacia confusa Stem Bark and Their Effect on the Browning Resistance of Fresh-Cut Asparagus Lettuce.

Tyrosinase inhibitors are capable of preventing unfavorable enzymatic browning of fruits and vegetables. In this study, the capacity of Acacia confusa stem bark proanthocyanidins (ASBPs) to inhibit tyrosinase activity was evaluated. ASBPs were shown to be a high-potential inhibitor of tyrosinase with IC50 values of 92.49 ± 4.70 and 61.74 ± 8.93 µg/mL when using L-tyrosine and L-DOPA as the substrate, respectively. The structural elucidation performed with UV-vis, FT-IR spectroscopy, ESI-MS and thiolysis coupled to HPLC-ESI-MS suggested that ASBPs had structural heterogeneity in monomer units and interflavan linkages and consisted mainly of procyanidins dominant with B-type linkages. To gain insights into the inhibitory mechanisms of ASBPs against tyrosinase, different spectroscopic and molecular docking methods were further conducted. Results validated that ASBPs possessed the ability to chelate copper ions and could prevent the oxidation process of substrates by tyrosinase. The hydrogen bond formed with Lys-376 residue played a key role in the binding force of ASBPs with tyrosinase that induced a certain alteration in the microenvironment and secondary structure of tyrosinase, resulting in the enzymatic activity being ultimately restricted. It was also observed that ASBPs treatment effectively inhibited the activities of PPO and POD to retard the surface browning of fresh-cut asparagus lettuce and thus extended their shelf-life. The results provided preliminary evidence supporting the exploitation of ASBPs into potential antibrowning agents for the fresh-cut food industry.

Diet composition and selection of Père David's deer in Hubei Shishou Milu National Nature Reserve, China.

Hubei Shishou Milu National Nature Reserve is an ideal place to restore the wild population of Père David's deer (Elaphurus davidianus). Understanding foraging ecology and diet composition is essential for assessing population development or establishing long-term effective conservation measures for endangered species. However, little is known about the diet composition of Père David's deer and its diet selection mechanism. In this study, we used stable isotope technology to investigate the diet composition of Père David's deer according to various tissues (i.e., fur, muscle, liver, heart, and feces) and seasons, and evaluated the correlation between the nutrient composition of plants and diet composition. Bayesian isotope analysis showed that the autumn and winter diet estimated by fur and fecal samples indicated a diet dominated by C3 grasses (42.7%-57.2%, mean), while the summer diet estimated by muscle and liver samples was dominated by C3 forbs (30.9%-41.6%, mean). The Pearson correlation test indicated that the contribution of winter diet composition reflected by fur and fecal samples was associated with correlations with crude protein (r = .666, p < .01) and soluble sugars (r = .695, p < .01). The results indicated that crude protein and soluble sugars were important factors influencing the winter diet selection of Père David's deer. In the context of the current reintroduction facing many challenges, such as habitat fragmentation, wetland degradation, and human disturbance, comprehensively evaluating the diet selection mechanism of Père David's deer under different resource specificities and temporal changes should be considered in the future.

Condensed tannins from Ulmus pumila L. leaves induce G2/M phase arrest and apoptosis via caspase-cascade activation in TFK-1 cholangiocarcinoma cells.

Condensed tannins the polyphenolic compounds that are widespread in plants have been proved to have antitumor potential. Here, we purified the bioactive condensed tannins from leaves of Ulmus pumila L. and explored their structural characteristics, antitumor effect on TFK-1 cholangiocarcinoma cells as well as the related potential mechanism. The UV-Vis, FT-IR spectroscopy, ESI-Full-MS, and thiolysis-HPLC-ESI-MS demonstrated that U. pumila condensed tannins (UCTs) consisted essentially of procyanidins with epicatechin as the main flavan-3-ol extension unit. The UCTs could significantly reduce the survival rate of human cholangiocarcinoma TFK-1, SK-CHA-1, and MZ-CHA-1 cells with the better inhibitory effect on TFK-1 cell proliferation. Flow cytometric assay showed that UCTs affected TFK-1 survival by G2/M phase arrest and inducing apoptosis in a dose-dependent manner. In addition, a total of 6592 differentially expressed genes (DEGs), consisting of 94 upregulated and 6498 downregulated DEGs, were identified between untreated and UCTs-treated TFK-1 cells using RNA-seq technology. Enrichment analysis based on the KEGG database revealed that these DEGs were closely associated with cell cycle and p53 apoptotic signaling pathways. Furthermore, qRT-PCR confirmed that treatment of UCTs to TFK-1 cells caused significant changes in the expression of cyclin E, cdc25 A, cytochrome c, caspase-3, and caspase-8. These results indicated that UCTs exhibited the growth inhibition effect on TFK-1 cells possibly via G2/M cell cycle arrest and activation of caspase-cascade to induce apoptosis, and had potential as an anti-cholangiocarcinoma drug for further development. PRACTICAL APPLICATIONS: Ulmus pumila L. as a valuable tree species has been widely used in fields of medicine and food. Condensed tannins, the polyphenolic compounds widespread in plants, have been proved to have antitumor potential and be safe to normal cells. In this study, the condensed tannins from leaves of U. pumila (UCTs) remarkably suppressed cholangiocarcinoma (CCA) cell viability possibly via G2/M cell cycle arrest and activation of caspase-cascade to induce apoptosis. The results provided evidence for the application of UCTs as a potential therapeutic drug for CCA tumor.

Conformational changes of tyrosinase caused by pentagalloylglucose binding: Implications for inhibitory effect and underlying mechanism.

Tyrosinase is a critical enzyme related to various pigmentation disorders and browning of fruits and vegetables. In this study, a novel inhibitor pentagalloylglucose (PGG) against tyrosinase was prepared from tannic acid with the chemical structure elucidated using HPLC, ESI-MS, 1H- and 13C NMR. Its inhibitory effect and the underlying mechanism on tyrosinase were explored by enzyme kinetics, UV-scanning, copper-ion chelation, fluorescence, circular dichroism, fourier transform infrared spectroscopy and molecular docking simulation. Results revealed that the yield of PGG reached 18.0% and the purity was up to 99.09%. PGG was a high-potential inhibitor of tyrosinase with IC50 values of (15.54 ± 0.56) × 10-6 and (50.89 ± 3.34) × 10-6 mol/L for monophenolase and diphenolase, respectively. PGG could disturb the formation of dopachrome and had strong capacity to chelate copper ions. The fluorescence of tyrosinase was efficiently quenched by PGG through a static mechanism. The binding of PGG to tyrosinase was a spontaneous exothermic process that induced unfolding of the tyrosinase structure to expose more buried hydrophobic residues. Docking results implied that PGG interacted with tyrosinase by forming hydrogen bonds with amino acid residues Glu-173, Glu-208, Lys-158, Lys-180, Gln-44 and Gln-159. This study would enhance our understanding of the inhibitory mechanism of PGG on tyrosinase at the molecular level and provide scientific guidance for the application of PGG in food and pharmaceutical industries.

Proanthocyanidins isolated from the leaves of Photinia × fraseri block the cell cycle and induce apoptosis by inhibiting tyrosinase activity in melanoma cells.

Tyrosinase is considered a molecular marker of melanoma, and few natural antitumor drugs targeting tyrosinase have been identified. In this study, proanthocyanidins (PAs) were isolated from the leaves of Photinia × fraseri and their structures were characterized by high performance liquid chromatography-electrospray ionization mass spectrometry (HPLC-ESI-MS), and matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOF MS) and the effects of antityrosinase activity were investigated. The results showed that the basic structural units of PAs are composed of catechin and epicatechin and that oligomer is the main component. PAs exhibited better antityrosinase activity via chelation of copper ions and by disturbing o-quinone production. Furthermore, analyses of the cell cycle, apoptosis rate, and regulation of melanin protein expression revealed preliminarily that PAs could affect melanin production by downregulating microphthalmia transcription factor (MITF) expression and by inhibiting the activities of tyrosinase and tyrosinase related protein 1 (TRP-1), leading to cell cycle arrest and apoptosis of melanoma cells. Collectively, our study demonstrated that PAs are potential tyrosinase inhibitors and have good antimelanoma effects. These findings provide a theoretical support for the application of tyrosinase inhibitors and for further drug development.

The interaction mechanism between liposome and whey protein: Effect of liposomal vesicles concentration.

The interaction mechanism between liposomes (Lips) and whey protein isolates (WPI) with different mass ratios was explored in this paper. After binding with different concentration of Lips, the changes in hydrophilic and hydrophobic regions of WPI were investigated with fluorescein isothiocyanate (FITC) and pyrene fluorescence probes. The spatial structure changes of WPI were further characterized by differential scanning calorimetry, Fourier transform infrared spectroscopy, and circular dichroism. The results indicated that the structure of WPI was changed due to binding with Lips in hydrophilic and hydrophobic groups. The binding process might result in the migration, recombination, and alignment of WPI and Lip groups. Moreover, the oil-water interfacial tension with WPI decreased from 9.20 mN/m to 3.29 mN/m upon increasing the Lip-to-WPI ratio. This work suggests that the physiochemical properties of Lip-WPI complexes could be manipulated by adjusting the Lip-to-WPI ratio. This study shed some light on the mechanism explanation of the WPI structural changes due to the interaction with Lips during food processing.

Whole-genome SNP markers reveal conservation status, signatures of selection, and introgression in Chinese Laiwu pigs.

Laiwu pigs are a Chinese indigenous breed that is renowned for its exceptionally high intramuscular fat content (average greater than 6%), providing an excellent genetic resource for the genetic improvement of meat quality of modern commercial pigs. To uncover genetic diversity, population structure, signature of selection, and potential exotic introgression in this breed, we sampled 238 Laiwu pigs from a state-supported conservation population and genotyped these individuals using GeneSeek 80K SNP BeadChip. We then conducted in-depth population genetics analyses for the Laiwu pig in a context of 1,116 pigs from 42 Eurasian diverse breeds. First, we show that the current Laiwu population has more abundant genetic diversity than the population of 18 years ago likely due to gene flow from European commercial breeds. Both neighbor-joining (NJ) and principal component analyses indicate the introgression of European haplotypes into Laiwu pigs. The admixture analysis reveals that an average 26.66% of Laiwu genetic components are of European origin. Then, we assigned the tested individuals to different families according to their clustering patterns in the NJ tree and proposed a family-based conservation strategy to reduce the risk of inbreeding depression in Laiwu pigs. Next, we explored three statistics (ROH and iHS and EigenGWAS) to identify a list of candidate genes for fat deposition, reproduction, and growth in Laiwu pigs. Last, we detected a strong signature of introgression from European pigs into Laiwu pigs at the GPC6 locus that regulates the growth of developing long bones. Further association analyses indicate that the introgressed GPC6 haplotype likely contributed to the improvement of growth performance in Laiwu pigs. Altogether, this study not only benefits the better conservation of the Laiwu pig, but also advances our knowledge of the poorly understood effect of human-mediated introgression on phenotypic traits in Chinese indigenous pigs.

HPLC-DAD fingerprints combined with chemometric techniques for the authentication of plucking seasons of Laoshan green tea.

Laoshan green teas plucked in summer and autumn were measured by high performance liquid chromatography-diode array detector (HPLC-DAD). After baseline correction, the fingerprints data were resolved by multivariate curve resolution-alternating least squares (MCR-ALS) and a total of 57 components were acquired. Relative concentrations of these components were afterwards applied to distinguish plucking seasons using principal component analysis (PCA), support vector machines (SVM) and partial least squares-discriminant analysis (PLS-DA). For both SVM and PLS-DA models, the total recognition rates of training set, cross-validation and testing set were 100%, 91.3% and 100%, respectively. Besides, three variable selection methods were employed to determine characteristic components for the authentication of summer and autumn teas. Results showed that PLS-DA model based on three characteristic components selected by VIP possesses identical predictive ability as the original model. This study demonstrated that our proposed strategy is competent for the authentication of plucking seasons of Laoshan green tea.

Inhibitory effects and molecular mechanism on mushroom tyrosinase by condensed tannins isolation from the fruit of Ziziphus jujuba Mill. var. spinosa (Bunge) Hu ex H. F. Chow.

The structure of extracted condensed tannin (CT) from the fruit of Sour jujube (Ziziphus jujuba Mill. var. spinosa (Bunge) Hu ex H. F. Chow) and the molecular mechanisms by which CT inhibits the activity of mushroom tyrosinase were investigated. The structure of CT was characterized by high performance liquid chromatography electrospray ionization mass spectrometry, and matrix-assisted laser desorption/ionization time-of-flight mass spectrometry. The kinetic assays were used to detect inhibition effect, type and mechanism. UV scanning, fluorescence quenching, copper interacting, o-quinone interaction and molecular docking assays were also used to reveal the molecular mechanisms by which CT inhibit tyrosinase. The results showed the structural units of CT containing afzelechin/epiafzelechin, catechin/epicatechin, and gallocatechin/epigallocatechin. Kinetic analysis showed that CT inhibits both the monophenolase and diphenolase activities of tyrosinase and exhibits reversible, mixed type mechanism. The fruit CT interacts primarily with the copper ions and specific amino acid residue (Asn191, Thr203, Ala202, Ser206, Met201, His194, His54, Glu182 and Ile42) in the active site of tyrosinase to disturb oxidation of substrates by tyrosinase. These results suggested the sour jujube fruit is a potential natural source of tyrosinase inhibitors, and has a potential to be used in food preservation, whitening cosmetics.

Transcriptome Analysis Reveals the Accumulation Mechanism of Anthocyanins in Buckwheat (Fagopyrum esculentum Moench) Cotyledons and Flowers.

Buckwheat (Fagopyrum esculentum) is a valuable crop which can produce multiple human beneficial secondary metabolites, for example, the anthocyanins in sprouts and flowers. However, as the predominant group of visible polyphenols in pigmentation, little is known about the molecular mechanisms underlying the anthocyanin biosynthesis within buckwheat. In this study, a comparative transcriptome analysis of green and red common buckwheat cultivars was carried out through RNA sequencing. Overall, 3727 and 5323 differently expressed genes (DEGs) were identified in flowers and cotyledons, respectively. Through GO and KEGG analysis, we revealed that DEGs in flowers and cotyledons are predominately involved in biosynthesis of anthocyanin. A total of 42 unigenes encoding 11 structural enzymes of the anthocyanin biosynthesis were identified as DEGs. We also identified some transcription factor families involved in the regulation of anthocyanin biosynthesis. Real-time qPCR validation of candidate genes was performed in flowers and cotyledons, and the results suggested that the high expression level of structural genes involved in anthocyanin biosynthetic pathway promotes anthocyanin accumulation. Our results provide the insight understanding for coloration of red common buckwheat.

Identification of Antioxidant and Anti-α-amylase Components in Lotus (Nelumbo nucifera, Gaertn.) Seed Epicarp.

Lotus seed epicarp, a byproduct of lotus seed production process, is usually discarded as a waste. In this study, antioxidant and anti-α-amylase activities of freeze-dried water and various methanol extracts of lotus seed epicarp were evaluated. The extract obtained by 80% methanol exhibited the strongest DPPH and ABTS radical scavenging activity and ferric reducing power, as well as the greatest inhibitory potential on α-amylase. The excellent antioxidant and α-amylase inhibitory activities of 80% methanol extract might be attributed to its highest concentrations of total phenolics, flavonoids, and condensed tannins. The inhibition kinetic analysis revealed that the 80% methanol extract was a reversible and uncompetitive-type inhibitor of α-amylase. Furthermore, based on MALDI-TOF-MS and thiolysis-HPLC-ESI-MS, the main active components present in 80% methanol extract were identified to be B-type heteropolymeric condensed tannins built up of mixtures of propelargonidins, procyanidins, and prodelphinidins, with the predominance of procyanidins and epicatechin as the main constitutive units. The results obtained suggested that lotus seed epicarp could be exploited as a potential source of natural antioxidants and α-amylase inhibitors.

Bulked Segregant RNA-seq Reveals Differential Expression and SNPs of Candidate Genes Associated with Waterlogging Tolerance in Maize.

Waterlogging has increasingly become one of the major constraints to maize productivity in some maize production zones because it causes serious yield loss. Bulked segregant RNA-seq (BSR-seq) has been widely applied to profile candidate genes and map associated Single Nucleotide Polymorphism (SNP) markers in many species. In this study, 10 waterlogging sensitive and eight tolerant inbred lines were selected from 60 maize inbred lines with waterlogging response determined and preselected by the International Maize and Wheat Improvement Center (CIMMYT) from over 400 tropical maize inbred lines. BSR-seq was performed to identify differentially expressed genes and SNPs associated with waterlogging tolerance. Upon waterlogging stress, 354 and 1094 genes were differentially expressed in the tolerant and sensitive pools, respectively, compared to untreated controls. When tolerant and sensitive pools were compared, 593 genes were differentially expressed under untreated and 431 genes under waterlogged conditions, of which 122 genes overlapped. To validate the BSR-seq results, the expression levels of six genes were determined by qRT-PCR. The qRT-PCR results were consistent with BSR-seq results. Comparison of allelic polymorphism in mRNA sequences between tolerant and sensitive pools revealed 165 (normal condition) and 128 (waterlogged condition) high-probability SNPs. We found 18 overlapping SNPs with genomic positions mapped. Eighteen SNPs were contained in 18 genes, and eight and nine of 18 genes were responsive to waterlogging stress in tolerant and sensitive lines, respectively. Six alleles of the 18 originated from tolerant pool were significantly up-regulated under waterlogging, but not those from sensitive pool. Importantly, one allele (GRMZM2G055704) of the six genes was mapped between umc1619 and umc1948 on chromosome 1 where a QTL associated with waterlogging tolerance was identified in a previous research, strongly indicating that GRMZM2G055704 is a candidate gene responsive to waterlogging. Our research contributes to the knowledge of the molecular mechanism for waterlogging tolerance in maize.

Relationships between degree of polymerization and antioxidant activities: a study on proanthocyanidins from the leaves of a medicinal mangrove plant Ceriops tagal.

Tannins from the leaves of a medicinal mangrove plant, Ceriops tagal, were purified and fractionated on Sephadex LH-20 columns. 13C nuclear magnetic resonance (13C-NMR), reversed/normal high performance liquid chromatography electrospray ionization mass spectrometry (HPLC-ESI MS) and matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDT-TOF MS) analysis showed that the tannins were predominantly B-type procyanidins with minor A-type linkages, galloyl and glucosyl substitutions, and a degree of polymerization (DP) up to 33. Thirteen subfractions of the procyanidins were successfully obtained by a modified fractionation method, and their antioxidant activities were investigated using 2,2-diphenyl-1-picrylhydrazyl (DPPH) scavenging capacity and ferric reducing antioxidant power (FRAP) method. All these subfractions exhibited potent antioxidant activities, and eleven of them showed significantly different mean DP (mDP) ranging from 1.43±0.04 to 31.77±1.15. Regression analysis demonstrated that antioxidant activities were positively correlative with mDP when around mDP <10, while dropped and then remained at a level similar to mDP = 5 with around 95 µg ml(-1) for DPPH scavenging activity and 4 mmol AAE g(-1) for FRAP value.

Antioxidant activities of fractions of polymeric procyanidins from stem bark of Acacia confusa.

The polymeric procyanidins extracted from Acacia confusa stem bark were fractionated with a step gradient of water, methanol and acetone on a Sephadex LH-20 column. The antioxidant activity of the collected fractions was investigated by the 2,2-diphenyl-1-picrylhydrazyl (DPPH) free radical scavenging and ferric reducing/antioxidant power (FRAP) assays. All fractions possessed potent antioxidant activity with the highest activity observed for fraction F9. The matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOF MS) and reversed-phase high performance liquid chromatography (RP-HPLC) analyses suggested that the collected fractions consisted primarily of oligomeric and polymeric procyanidins, with different polymer ranges and most abundant polymer size. For each fraction, catechin and epicatechin were present as both terminal and extension units, and epicatechin was the major component in the extended chain. The mean degree of polymerization (mDP) of each fraction differed, ranging from 1.68 (fraction F2) to 17.31 (fraction F11). There was a relationship between antioxidant activity (IC50/DPPH and FRAP) and mDP (R(2) (DPPH) = 0.861, P = 0.006 and R(2) (FRAP) = 0.608, P = 0.038), respectively. However, the highest antioxidant activity of fraction (F9) was not coincident with the maximum mDP of fraction (F11).

Identification and genetic effects of a novel polymorphism in the distal promoter region of porcine leptin gene.

Leptin is a hormone expressed mainly in white adipose tissue. It acts on satiety centers in the hypothalamus, and by binding to particular receptor OB-Rb, plays a crucial role in controlling appetite, body weight, fat amount and total energy balance. In this study, a novel single nucleotide polymorphism (SNP), i.e., SNP G-2863A, was identified in the distal promoter region of porcine leptin gene. Totally 780 individuals of Duroc, Yorkshire, Laiwu, Lulai Black breeds, and Landrace × Yorkshire crossbred were genotyped by PCR-SSCP approach. The effects of SNP G-2863A on mRNA and serum protein levels of leptin as well as in driving transcription were examined. The results showed that, except for Duroc and Yorkshire pigs, three genotypes of GG, GA and AA were detected. Allele G occurred with a higher frequency in western breeds and Landrace × Yorkshire crossbred pigs, whereas with a lower frequency in Laiwu pigs. Statistical analysis indicated that there were consistent trends toward higher levels in animals with genotype GG than with GA or AA genotypes in backfat thickness of both Landrace × Yorkshire crossbred and Lulai Black pigs, in backfat leptin mRNA and the circulating serum leptin protein level in half-sibling Lulai Black pigs, and the activity of allele G was significantly higher than allele A (P < 0.01) in driving reporter gene expression. These results suggest that SNP G-2863A is a potential DNA marker for backfat thickness and has a regulatory role in leptin transcription.

Antioxidant activities of extract and fractions from the hypocotyls of the mangrove plant Kandelia candel.

The antioxidant activities of 70% acetone extract (70% AE) from the hypocotyls of the mangrove plant Kandelia candel and its fractions of petroleum ether (PF), ethyl acetate (EF), water (WF), and the LF (WF fraction further purified through a Sephadex LH-20 column), were investigated by the 1,1-diphenyl-2-picrylhydrazyl (DPPH) free radical scavenging and ferric reducing/antioxidant power (FRAP) assays. The results showed that all the extract and fractions possessed potent antioxidant activity. There was a significant linear correlation between the total phenolics concentration and the ferric reducing power or free radical scavenging activity of the extract and fractions. Among the extract and fractions, the LF fraction exhibits the best antioxidant performance. The MALDT-TOF MS and HPLC analyses revealed that the phenolic compounds associated with the antioxidant activity of the LF fraction contains a large number of procyanidins and a small amount of prodelphinidins, and the epicatechin is the main extension unit.

Antioxidant tannins from stem bark and fine root of Casuarina equisetifolia.

Structures of condensed tannins from the stem bark and fine root of Casuarina equisetifolia were identified using MALDI-TOF MS and HPLC analyses. The condensed tannins from stem bark and fine root consist predominantly of procyanidin combined with prodelphinidin and propelargonidin, and epicatechin is the main extension unit. The condensed tannins had different polymer chain lengths, varying from trimers to tridecamer for stem bark and to pentadecamer for fine root. The antioxidant activities were measured by two models: 1,1-diphenyl-2- picrylhydrazyl (DPPH) radical scavenging activity and ferric reducing/ antioxidant power (FRAP). The condensed tannins extracted from C. equisetifolia showed very good DPPH radical scavenging activity and ferric reducing/ antioxidant power, suggesting that these extracts may be considered as new sources of natural antioxidants for food and nutraceutical products.

MALDI-TOF MS analysis of condensed tannins with potent antioxidant activity from the leaf, stem bark and root bark of Acacia confusa.

The structures of the condensed tannins from leaf, stem bark and root bark of Acacia confusa were characterized by matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOF MS) analysis, and their antioxidant activities were measured using 1,1-diphenyl-2-picrylhydrazyl (DPPH) free radical scavenging and ferric reducing/antioxidant power (FRAP) assays. The results showed that the condensed tannins from stem bark and root bark include propelargonidin and procyanidin, and the leaf condensed tannins include propelargonidin, procyanidin and prodelphinidin, all with the procyanidin dominating. The condensed tannins had different polymer chain lengths, varying from trimers to undecamers for leaf and root bark and to dodecamers for stem bark. The condensed tannins extracted from the leaf, stem bark and root bark all showed a very good DPPH radical scavenging activity and ferric reducing power.

Condensed tannins from mangrove species Kandelia candel and Rhizophora mangle and their antioxidant activity.

The structures of condensed tannins isolated from two mangrove species, Kandelia candel and Rhizophora mangle, were characterized by 13C nuclear magnetic resonance (NMR) spectroscopy and matrix assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOF MS) analyses. Results demonstrate that large heterogeneity occurs in degree of polymerization, pattern of hydroxylation, and substitution with monosaccharides in the structures of the condensed tannins. Condensed tannin oligomers from K. candel and R. mangle were shown to be heterogeneous mixtures consisting of procyanidin and prodelphinidin structural units with the former dominating. The MALDI-TOF mass spectra contained masses corresponding to a distinct oligomeric series of glycosylated heteropoly flavan units. In addition, condensed tannins from two mangrove plants were screened for their potential antioxidant activities using 1,1-diphenyl-2-picrylhydrazyl (DPPH) and ferric reducing antioxidant power (FRAP) model systems.