Protein structures of common bean (Phaseolus vulgaris) alpha-amylase inhibitors

Two nucleotide sequences for genes that encode alpha-amylase inhibitor 4 (alphaAI-4) from white kidney bean (WKB) cv. 858, designated gene alphaAI-4 (Accession No. ), and alpha-amylase inhibitor 5 (alphaAI-5) from black bean (BB), designated gene alphaAI-5 (Accession No. ), were determined. Genes alphaAI-4 and alphaAI-5 encode 244 amino acid prepro-alphaAI-4 and prepro-alphaAI-5 polypeptides that are 93 and 95% identical with alpha-amylase inhibitor l (alphaAI-l; Hoffman, L. M.; Ma, Y.; Barker, R. F.Nucleic Acids Res. 1982, 10, 7819-7828), 40 and 43% identical with red kidney bean lectin, and 52 and 55% identical with arcelin l of wild-type bean. The high degree of sequence similarity indicates the evolutionary relationship among these genes. PCR analysis of genomic DNA purified from six genotypes of Phaseolus vulgaris showed very similar band patterns in 2% agarose gel, another indication of the conserved size homology among these genes. Proteolytic processing sites were located between Asn77 and Ser78 for pro-alphaAI-4 and pro-alphaAI-5. A bend next to Asn77 in three-dimensional model structures of alphaAI-4 and alphaAI-5 proinhibitors indicates that the proteolytic cleavage is necessary to remove the conformational constraint for activation to the mature protein. Mature WKB alphaAI-4 was composed of four subunits (2alpha2beta) and had a molecular weight of 50000 determined by multiangle laser light scattering and 56714 determined by laser-assisted time-of-flight mass spectrometry.     

Simplified electrophoretic assay for human salivary alpha-amylase inhibitor detection in cereal seed flours

Alpha-amylase inhibitors are antinutritional proteins largely found in cereal seeds. An in-gel assay was developed that allowed the rapid screening of these compounds in complex seed extracts. The assay was based on the electrophoretic separation of the extract proteins on starch-containing gels, followed by the detection of alpha-amylase-inhibiting proteins after incubation of the gel in an alpha-amylase solution; inhibitors were revealed by a staining method based on iodine binding to nondigested starch. The one-dimensional method can be useful to test inhibitory activity of purified proteins or to assay fractions recovered during a purification procedure. A two-dimensional (IEF x PAGE) non-denaturing system with second-dimension separation on starch-PAGE was also developed; the technique allowed the screening of complex protein mixtures for multiple inhibitory proteins. The newly developed assay method was used to test the presence of inhibitory activity in a crude extract from wheat flour, and it was validated by comparing in-gel and in-solution assays of commercially available alpha-amylase inhibitors.     

Italian common bean landraces: diversity and population structure

Phaseolus vulgaris L. is an important species that originated in Mesoamerica. A Mesoamerican and an Andean gene pool are usually distinguished in the domesticated forms. Many bean landraces are still cultivated in Italy and the Department of Applied Biology maintains an ex situ collection of 146 landraces. Although protection schemes are being developed in Italy, most landraces are extinct or at risk of extinction. To facilitate their conservation and use, geographical, morphological, biochemical and molecular (SSR) data were collected and analysed to estimate the diversity and the genetic structure of the collection. Data confirmed that both the Mesoamerican and the Andean gene pools were introduced in Italy and, although a distinction between the two gene pools exists, the Italian landrace diversity is clearly structured in three clusters that are not simply ascribable to the original gene pools. The observed structure appears also to be due to adaptation to the different environmental conditions determined by altitude. This was confirmed by assessing the presence of selective effects for some of the SSR used in this study. Finally, a certain extent of admixture in Italian landrace diversity suggests past (or recurring) hybridisation events among gene pools. The combined use of morphological, biochemical and molecular data clearly distinguished almost all the landraces. The data gathered here can assist landrace in situ protection schemes that are being developed in Italy, be used to register landraces in the European common catalogue of ‘conservation varieties’ for seed commercialisation and contribute to a better use of Italian common bean diversity in breeding for organic and conventional production systems.     

Transgenic sorghum with altered kafirin synthesis: kafirin solubility, polymerization, and protein digestion

Transgenic sorghum (TG) lines with altered kafirin synthesis, particularly suppression of γ-kafirin synthesis, and improved protein quality have been developed. The proportion of kafirin extracted with 60% tert-butyl alcohol alone was greatly increased in the TG lines. However, the total amount of kafirin remained unchanged. Further, in the TG lines, the kafirin was much less polymerized by disulfide bonding. There was also evidence of compensatory synthesis of other kafirin proteins. Cooked protein digestibility was increased in the TG form, even after removal of interfering starch. The TG protein bodies were intermediate in appearance between the normal type and the invaginated high digestibility mutants. Hence, the increased protein digestibility of these TG lines is probably related to their lower levels of disulfide-bonded kafirin polymerization, allowing better access of proteases. This work appears to confirm that disulfide bond formation in kafirin is responsible for the reduced protein digestibility of cooked sorghum.     

Identification of an alpha-amylase inhibitor from Pterodon pubescens with ability to inhibit cowpea weevil digestive enzymes

Cowpea seeds (Vigna ungiculata) are widely cultivated by poor farmers in Latin America and Africa and are often severely damaged by the cowpea weevil Callosobruchus maculatus. A proteinaceous inhibitor of cowpea weevil digestive enzymes, PpAI, was purified from white sucupira seeds (Pterodon pubescens) and biochemically characterized in this study. Proteins were extracted from seeds and precipitated with ammonium sulfate at 100% saturation. This fraction was applied onto a Red-sepharose CL-6B column, and the retained peak showed 70% inhibitory activity toward larval C. maculatus digestive alpha-amylases. The retained peak was then purified using an analytical reversed-phase HPLC column. Purified PpAI showed 65% inhibitory activity against larval C. maculatus enzymes. Enzymatic assays also showed that the purified P. pubescens inhibitor was unable to reduce the activity of mammalian alpha-amylases, suggesting specificity toward insect enzymes. Moreover, artificial seeds containing PpAI were able to reduce larval weight by 36% and cause 55% mortality. Mass spectrometry and SDS-PAGE analyses indicated that PpAI showed a molecular mass of approximately 5.0 kDa. This alpha-amylase inhibitor, coming from a native Cerrado plant, could be used to construct a genetically engineered cowpea with enhanced resistance against weevil pests.     

Combined consumption of soy germ and tomato powders results in altered isoflavone and carotenoid bioavailability in rats

The efficacy of combinations of food for enhanced anticancer activity is of clinical interest, but there is limited information on the effect of combined consumption on bioactive bioavailability. Male Copenhagen rats consumed diets containing 10% tomato powder (TP), 2% soy germ (SG), neither, or a combination (TP+SG) for 25 weeks (n = 63) or 7 days (n = 24). After 7 days, serum carotenoids were significantly lower after TP+SG feeding compared to TP alone. After 25 weeks, the TP+SG group had significantly lower lycopene and β-carotene concentration in the testes, seminal vesicles, and ventral prostate compared to the TP group and significantly higher urinary isoflavone excretion compared to the SG group. These differences were not explained by mRNA expression of scavenger receptor class B type I, carotene 15,15'-monooxygenase I, carotene 9',10'-monooxygenase II, or activity of hepatic detoxification enzymes. The results suggest interactions between soy germ and tomato powder that enhance isoflavone absorption but reduce carotenoid bioavailability.     

The relationship between boron soil test results and boron uptake by bean plants

Abstract

Boron sensitive crops, kidney beans and soybeans, were grown in pots containing soil collected from a beet field and a nearby pasture. Two soil extraction procedures were used to measure boron concentrations in the soils. Dilute acid was used to extract what is believed to be readily available boron. A modified‐Soxhlet apparatus, which employed continuous leaching with hot water, measured what is believed to be slowly available boron. Plant boron status was determined by analyzing the above ground portion of the plants grown in two soils. The amount of boron in the plant tops provides an indication of biologically available boron or that boron actually available to plants. Although kidney beans and soybeans extracted more boron from the beet soil, both soil extraction procedures indicated that the concentration of boron was higher in the pasture soil. Neither extraction procedure proved reliable in predicting plant response.     

Molecular cloning and characterization of an alpha-amylase occurring in the pulp of ripening bananas and its expression in Pichia pastoris

Alpha-amylases (EC 3.2.1.1) are glycosyl hydrolases with endoglycolytic activity on the alpha-1,4-d-glucosidic linkages in starch. In bananas, the mobilization of starch accounts for sugar accumulation during ripening, and among several hydrolytic enzymes, alpha-amylase is the only enzyme argued to be able to attack the intact granules, indicating a pivotal role for this enzyme. A 1953 bp full-length banana alpha-amylase cDNA (MAmy), encoded for a sequence of 416 amino acids, was cloned and used for heterologous expression in Pichia pastoris. The cloned MAmy presented the highly conserved motifs common to alpha-amylases, and the amylolytic activity of the extracts from yeast transformed with MAmy demonstrated that it encodes for a functional alpha-amylase, suggesting a putative role for this gene in starch degradation during fruit ripening.     

Cultivar effects on nitrogen fixation in peas and lentils

Increasing nitrogen fixation in legume crops could increase cropping productivity and reduce nitrogen fertilizer use. Studies have found that crop genotype, rhizobial strain, and occasionally genotype-specific interactions affect N fixation, but this knowledge has not yet been used to evaluate or breed for greater N fixation in US crops. In this study five USDA varieties of lentils (Lens culinaris Medik.) and five varieties of peas (Pisum sativum L.) were tested with 13 to 15 commercially available strains of Rhizobium leguminoserum bv. viciae to identify the better N fixing rhizobial strains, crop varieties, and specific pairings. Peas and lentils inoculated with individual strains were grown in growth chambers for 6 week. Plants received (¹⁵NH₄)₂ SO₄ (5 at.%) starter fertilizer to measure N fixation by isotope dilution. Below- and above-ground biomass, numbers of nodules, and the proportion of plant N supplied by fixation (PNF) were determined. The percent of N fixed was significantly affected by crop variety and significantly correlated with number of nodules in both lentils and peas. This implies that one strategy for enhancing crop N fixation is developing varieties that have higher rhizobium infection rates. Total N fixation in lentils was significantly influenced by both crop variety and rhizobial strain. Eston variety lentil and Shawnee variety pea had the highest PNF of 80.8% and 91.3%, respectively. The different strains of R. leguminoserum affected PNF in lentils but not in peas. These findings suggest that N fixation improvement in lentils and peas may be addressed most effectively by breeding crops for greater N fixation hosting capacity.     

Partial isolation and characterization of a cysteine proteinase inhibitor from Lima bean (Phaseolus lunatus)

Lima beans (Phaseolus lunatus) have been shown to contain cysteine proteinase inhibitor (CPI) activity, but the CPI has not been isolated or characterized. Accordingly, our objective was to isolate and partially characterize a CPI from lima bean. The isolation scheme included water extraction of lima bean flour followed by a chromatography series using DEAE Sepharose, Phenyl Sepharose, hydroxyapatite, and reversed-phase high performance liquid chromatography. This scheme resulted in the partial purification of a approximately 20 000-dalton protein with high inhibitory activity against papain. This isolated lima bean CPI had an N-terminal sequence homologous with other members of the cystatin class of CPIs. The protein was relatively heat labile; suggesting it could be inactivated with normal cooking, which is favorable for its use in transforming plants to create insect resistance.     

不同温度处理对红芸豆蛋白热稳定性及结构的影响

为探究加热过程中红芸豆分离蛋白（Red Kidney Bean Protein Isolate, KPI）溶解特性和结构特性变化及评估不同温度（50～95 ℃）处理对KPI溶液热聚集特性的影响。该研究以不同温度处理KPI溶液为研究对象,采用热力学和光谱学对其热聚集特性进行分析研究。结果表明：随处理温度升高,红芸豆蛋白溶解度呈先升后降趋势,70 ℃时蛋白溶解度达到最高值82.68%,温度升高至95℃时,溶解度下降至65.63%;电泳结果显示,90 ℃处理蛋白上清液电泳图谱中出现一条分子量约为135 kDa的新条带。随温度升高,总巯基数量则呈下降趋势,游离巯基呈先升后降趋势。随温度上升,加热造成蛋白α-螺旋结构占比呈下降趋势,不规则结构占比呈上升趋势,β-折叠和β-转角变化幅度不大,而KPI内源荧光的最大发射波长呈红移趋势。研究结果为实践生产热处理过程中红芸豆蛋白结构和稳定性的变化规律和红芸豆食品热加工工艺优化和质量控制提供了理论基础。     

Significance of phenol-protein interactions in modifying the antioxidant capacity of peas

The aim of this study is to evaluate the contribution of phenol-protein interaction (PPI) and its binding activity in strengthening the antioxidant capacity of peas after immersion with five phenolics under different heating conditions. The results showed that hydroxycinnamic acids (ferulic acid, coumaric acid, or caffeic acid) are better than hydroxybenzoic acid (gallic acid) in increasing superoxide dismutase (SOD) heat stability. In addition, the higher the temperature, the more evident was the enhancement. DPPH scavenging capacity and reducing power showed the same tendency. Further kinetic analysis proved that SOD with the best heat stability showed the largest activation energy during heating. Moreover, the contribution of phenol-protein binding to the antioxidant capacity was further estimated through complex purification and calculation of binding capacity. Coumaric acid was the most efficient phenolic compound in increasing antioxidant capacity and showed the highest binding capacity with pea protein. These results indicated that phenolic compounds might enhance the antioxidant capacity of peas during heating through phenol-protein interaction.     

Selenium bioavailability from naturally produced high-selenium peas and oats in selenium-deficient rats

This study determined the bioavailability of selenium (Se) from yellow peas and oats harvested from the high-Se soil of South Dakota, United States. The Se concentrations were 13.5 ± 0.2 and 2.5 ± 0.1 mg/kg (dry weight) for peas and oats, respectively. Male weanling Sprague-Dawley rats were depleted of Se by feeding them a 30% Torula yeast-based diet (4.1 μg Se/kg) for 56 days, and then they were replenished with Se for an additional 50 days by feeding them the same diet supplemented with 20, 30, or 40 μg Se/kg from peas or oats, respectively. Selenium bioavailability was determined on the basis of the restoration of Se-dependent enzyme activities and tissue Se concentrations in Se-depleted rats, comparing those responses for yellow peas and oats to those for l-selenomethionine (SeMet; used as a reference) by using a slope-ratio method. Dietary supplementation with peas or oats resulted in linear or log-linear, dose-dependent increases in glutathione peroxidase activities in blood and liver and in thioredoxin reductase activity in liver. Supplementation with peas or oats resulted in linear or log-linear, dose-dependent increases in Se concentrations of plasma, liver, gastrocnemius muscle, and kidneys. The overall bioavailability was approximately 88% for Se from yellow peas and 92% from oats, compared to SeMet. It was concluded that Se from naturally produced high-Se yellow peas or oats is highly bioavailable in this model and that these high-Se foods may be a good dietary source of Se.     

Biodiversity and trophic structure of soil nematode communities are altered following woody plant invasion of grassland

Woody plant encroachment is an important land cover change in dryland ecosystems throughout the world, and frequently alters above and belowground primary productivity, hydrology, and soil microbial biomass and activity. However, there is little known regarding the impact of this geographically widespread vegetation change on the biodiversity and trophic structure of soil fauna. Nematodes represent a major component of the soil microfauna whose community composition and trophic structure could be strongly influenced by the changes in ecosystem structure and function that accompany woody encroachment. Our purpose was to characterize nematode community composition and trophic structure along a grassland to woodland chronosequence in the Rio Grande Plains of southern Texas. Research was conducted at the La Copita Research Area where woody encroachment has been documented previously. Soil cores (0–10 cm) were collected in fall 2006 and spring 2007 from remnant grasslands and woody plant stands ranging in age from 15 to 86 years, and nematodes were extracted by sugar centrifugation. Neither nematode densities (3200–13,800 individuals kg⁻¹ soil) nor family richness (15–19 families 100 g⁻¹ soil) were altered by woody encroachment. However, family evenness decreased dramatically in woody stands >30 years old. This change in evenness corresponded to modifications in the trophic structure of nematode communities following grassland to woodland conversion. Although root biomass was 2–5× greater in wooded areas, root-parasitic nematodes decreased from 40% of all nematodes in grasslands to <10% in the older wooded areas, suggesting the quality (C:N or biochemical defenses) of woody plant root tissue could be limiting root-parasites. In contrast, bacterivores increased from 30% of nematodes in grasslands to 70–80% in older woody patches. This large increase in bacterivores may be a response to the 1.5–2.5× increase in soil microbial biomass (bacteria + fungi) following woody encroachment. Therefore, while energy flow through grassland nematode communities appears to be distributed nearly equally among herbivory, fungivory and bacterivory, the energy flow through nematode communities in wooded areas appears to be based primarily on bacterivory. We speculate that these shifts in nematode community composition and trophic structure could have important implications for ecosystem patterns and processes. First, the low abundance of root-parasitic nematodes (and presumably root herbivory) under woody plants may be one mechanism by which woody plants are able to establish and compete effectively with grasses during succession from grassland to woodland. Second, the large increase in bacterivores following woody encroachment likely accelerates microbial turnover and the mineralization of N, thereby providing a feedback that enables the persistence of N-rich woody plant communities.     

流感复合多表位疫苗的设计及小鼠免疫研究

鉴于目前出现了多种亚型禽流感病毒共存的局面,研究多价流感疫苗具有重要意义。根据各表位的免疫学特性,结合分子生物学信息软件的模拟功能,以H 3、H 9亚型流感病毒的HA抗原表位、流感病毒的其他主要抗原(NP、NA、M)表位的基因为基础,再附以K ozak序列和适当的酶切位点,设计并合成大小为765 bp的复合多表位基因盒-Ep。i将Ep i基因克隆入真核表达载体pIRES1neo中,构建DNA重组体pIR-Ep i;将H 7HA、Ep、iH 5HA基因以融合表达方式克隆到pIRES1neo中,构建了DNA重组体pIRE-H 57-Ep。i以上述构建的DNA重组体与鸡痘病毒重组株对BALB/c小鼠进行免疫接种后,检测体液与细胞免疫指标。研究结果表明,流感病毒复合多表位DNA重组体pIRE-H 57-Ep、ipIRE-Ep i免疫组小鼠均能产生针对H 3亚型流感病毒的特异性抗体,抗体效价(1∶1 600~1∶6 400)低于灭活疫苗免疫组(1∶12 800),但均高于其他对照免疫组(P<0.01)。pIRE-H 57-Ep i免疫组抗H 5、H 7 HA抗体效价分别为1∶12 800和1∶6 400,均高于其他免疫组(P<0.05)。pIRE-Ep i免疫组抗H 5、H 7HA抗体效价(1∶200,1∶100)较低,与其他对照免疫组差异不显著。pIRE-H 57-Ep i与pIRE-Ep i免疫组抗H 9亚型A IV的HA抗体效价(1∶6 400,1∶3 200)明显高于其他免疫组(P<0.05)。与PBS对照组及空质粒pIRES1neo对照组比较,用所构建的重组体免疫的各试验组小鼠的T淋巴细胞亚类CD 4 和CD 8 的数量显著提高(P<0.05)。pIRE-H 57-Ep i与pIRE-Ep i试验组的CD 4 与CD 8 淋巴细胞的数量较灭活苗显著增多(P<0.05),而各重组体免疫组之间差异不显著。此外,所有组的CD 4 /CD 8 比值均稳定在1.5~2.0,表明无异常免疫应答出现。EL ISPOT检测小鼠脾淋巴细胞分泌IFNγ-斑点数实验结果表明,pIRE-H 57-Ep、ipIRE-Ep i试验组的IFNγ-斑点数量(>70)比灭活苗(<40)显著增多(P<0.05),而各重组体免疫组之间差异不显著。上述结果说明,所构建的DNA重组体有良好的免疫原性,为最终获得能同时预防多种亚型流感病毒的多价疫苗奠定了基础。     

阿魏酸诱导蚕豆枯萎病发生及根系组织结构损伤的化感效应

  【目的】  酚酸类化合物是多种农作物根际土壤中常见的自毒物质，化感自毒物质与土传病害发生密切相关。研究阿魏酸对枯萎病发生的促进效应及机理，为阐明连作自毒物质–病原菌–寄主抗病性互作效应提供参考。  【方法】  采用水培试验研究阿魏酸对蚕豆幼苗生长和枯萎病发生的影响。在蚕豆幼苗长至4～6片真叶时，将其移入2 L Hoagland 营养液中进行培养，其中阿魏酸浓度分别为0、50、100、200 mg/L。待阿魏酸处理2 天后，加入25 mL 1 × 106 cfu/mL的尖孢镰刀菌孢子悬浮液。继续培养40天后，取样调查植株生长状况和枯萎病发病率。利用显微镜观察蚕豆根系细胞组织结构的变化，通过室内培养试验研究尖孢镰刀菌菌丝生长和致病力对阿魏酸胁迫的响应。  【结果】  与无添加阿魏酸 (0 mg/L) 处理相比，添加阿魏酸处理显著抑制蚕豆幼苗的生长，且阿魏酸浓度越高抑制作用越强。本试验条件下，阿魏酸处理显著提高蚕豆枯萎病发病率300.0%～500.0%，显著增加病情指数113.3%～1666.7%，发病率和病情指数均在阿魏酸处理浓度200 mg/L下达到最大值。阿魏酸处理抑制尖孢镰刀菌的菌丝生长，显著提高尖孢镰刀菌产生的果胶酶、纤维素酶、淀粉酶和蛋白酶活性44.8%～59.0%、78.2%～145.6%、975.6%～2435.4%和165.1%～622.9%；显著提高枯萎酸含量107.6%～236.2%。阿魏酸胁迫下，蚕豆根系表皮细胞扭曲变形，木质部导管变细，导管壁增厚，胶状物和内含物充满整个细胞，阻碍营养物质和水分的正常运输，进而加速蚕豆枯萎死亡。  【结论】  阿魏酸胁迫虽然抑制尖孢镰刀菌的菌丝生长，但显著提高蚕豆根系细胞壁降解酶活性和枯萎酸含量，进而增加尖孢镰刀菌致病力，加速根系细胞组织结构损伤，促进尖孢镰刀菌侵入蚕豆根系，加剧枯萎病发生和危害。阿魏酸在蚕豆连作障碍中扮演着初始诱因的角色。     

Phytochemicals of black bean seed coats: isolation, structure elucidation, and their antiproliferative and antioxidative activities

Bioactivity-guided fractionation of black bean (Phaseolus vulgaris) seed coats was used to determine the chemical identity of bioactive constituents, which showed potent antiproliferative and antioxidative activities. Twenty-four compounds including 12 triterpenoids, 7 flavonoids, and 5 other phytochemicals were isolated using gradient solvent fractionation, silica gel and ODS columns, and semipreparative and preparative HPLC. Their chemical structures were identified using MS, NMR, and X-ray diffraction analysis. Antiproliferative activities of isolated compounds against Caco-2 human colon cancer cells, HepG2 human liver cancer cells, and MCF-7 human breast cancer cells were evaluated. Among the compounds isolated, compounds 1, 2, 6, 7, 8, 13, 14, 15, 16, 19, and 20 showed potent inhibitory activities against the proliferation of HepG2 cells, with EC50 values of 238.8 +/- 19.2, 120.6 +/- 7.3, 94.4 +/- 3.4, 98.9 +/- 3.3, 32.1 +/- 6.3, 306.4 +/- 131.3, 156.9 +/- 11.8, 410.3 +/- 17.4, 435.9 +/- 47.7, 202.3 +/- 42.9, and 779.3 +/- 37.4 microM, respectively. Compounds 1, 2, 3, 5, 6, 7, 8, 9, 10, 11, 14, 15, 19, and 20 showed potent antiproliferative activities against Caco-2 cell growth, with EC50 values of 179.9 +/- 16.9, 128.8 +/- 11.6, 197.8 +/- 4.2, 105.9 +/- 4.7, 13.9 +/- 2.8, 35.1 +/- 2.9, 31.2 +/- 0.5, 71.1 +/- 11.9, 40.8 +/- 4.1, 55.7 +/- 8.1, 299.8 +/- 17.3, 533.3 +/- 126.0, 291.2 +/- 1.0, and 717.2 +/- 104.8 microM, respectively. Compounds 5, 7, 8, 9, 11, 19, 20 showed potent antiproliferative activities against MCF-7 cell growth in a dose-dependent manner, with EC50 values of 129.4 +/- 9.0, 79.5 +/- 1.0, 140.1 +/- 31.8, 119.0 +/- 7.2, 84.6 +/- 1.7, 186.6 +/- 21.1, and 1308 +/- 69.9 microM, respectively. Six flavonoids (compounds 14-19) showed potent antioxidant activity. These results showed the phytochemical extracts of black bean seed coats have potent antioxidant and antiproliferative activities.     

Different polyphenolic components of soft fruits inhibit alpha-amylase and alpha-glucosidase

Polyphenol-rich extracts from soft fruits were tested for their ability to inhibit alpha-amylase and alpha-glucosidase. All extracts tested caused some inhibition of alpha-amylase, but there was a 10-fold difference between the least and most effective extracts. Strawberry and raspberry extracts were more effective alpha-amylase inhibitors than blueberry, blackcurrant, or red cabbage. Conversely, alpha-glucosidase was more readily inhibited by blueberry and blackcurrant extracts. The extent of inhibition of alpha-glucosidase was related to their anthocyanin content. For example, blueberry and blackcurrant extracts, which have the highest anthocyanin content, were the most effective inhibitors of alpha-glucosidase. The extracts most effective in inhibiting alpha-amylase (strawberry and raspberry) contain appreciable amounts of soluble tannins. Other tannin-rich extracts (red grape, red wine, and green tea) were also effective inhibitors of alpha-amylase. Indeed, removing tannins from strawberry extracts with gelatin also removed inhibition. Fractionation of raspberry extracts on Sephadex LH-20 produced an unbound fraction enriched in anthocyanins and a bound fraction enriched in tannin-like polyphenols. The unbound anthocyanin-enriched fraction was more effective against alpha-glucosidase than the original extract, whereas the alpha-amylase inhibitors were concentrated in the bound fraction. The LH-20 bound sample was separated by preparative HPLC, and fractions were assayed for inhibition of alpha-amylase. The inhibitory components were identified as ellagitannins using LC-MS-MS. This study suggests that different polyphenolic components of fruits may influence different steps in starch digestion in a synergistic manner.     

Population structure and genetic differentiation among the USDA common bean (Phaseolus vulgaris L.) core collection

Genetic diversity data were collected from a large population of common bean (Phaseolus vulgaris L.) landraces representing the United States Department of Agriculture core collection. The data were based on microsatellite data from all linkage groups. A procedure was developed to determine if we collected sufficient marker data to adequately estimated pairwise diversity. The diversity data were used to define populations using distance and model-based approaches. Genetic differentiation and genetic isolation by distance data were collected. Diversity was also compared for markers linked and unlinked to domestication loci. Using a model-based approach, the landraces were divided into the traditional Middle American and Andean gene pools. Diversity was greater for the Middle American gene pool. Six Middle American and three Andean subpopulations were defined, and the Middle American subpopulations exhibited strong geographic identity. Unlike other studies, seed size varied considerably with subpopulations, and a number of the subpopulations contained landraces from multiple common bean races. All of the subpopulations were highly differentiated, with the Middle American subpopulations showing the greatest differentiation. Genetic isolation by distance was observed among the Middle American and Andean subpopulations but not among subpopulations within a gene pool. Within each gene pool, diversity was lower for markers linked to domestication loci.     

Nutritional assessment in vitro and in vivo of raw and extruded peas (Pisum sativum L.)

The effects of extrusion cooking on the nutritional properties of Pisum sativum L. have been evaluated in vitro and in vivo. The treatment greatly elevated protein and starch digestibility in vitro. Also, the amounts of intact starch diminished while total free sugars increased. In addition, the levels of antinutritional factors, such as protease inhibitors and lectins, were greatly decreased. Concentrations of methionine and cystine were low in raw peas and were further reduced by extrusion treatment. The nutritional performance of rats fed extruded pea diets for 15 days was no better than that of rats given raw pea diet. This was due to the overriding effects of amino acid deficiencies in the diets. Weight gains by rats fed extruded pea diets supplemented with amino acids were, however, much higher than those achieved by rats fed supplemented raw pea diets. Food transformation index and protein efficiency ratio values were also greatly improved. Extrusion treatment did therefore significantly improve the nutritional quality of peas.