Fracture toughness of wet and dry Pinus radiata

Pinus radiata were determined using a three-point bend test and a compact-shear specimen test respectively. The fracture toughness across the grain (LT and LR) in mode 1 was ten times greater than in other directions for both wet and dry specimens. The mode 1 fracture toughness of wet wood was lower than dry wood in every orientation except TR. The mode 2 fracture toughness for dry wood was found for all directions except the longitudinal ones (LT and LR). In the longitudinal direction, mode 2 fracture did not occur, as the wood failed in compression before its shear limits were reached. In wet wood, pure mode 2 fracture occurred only in the RL direction. In other directions, the fracture did not originate from the notch tip, or the wood fractured in a mixed mode.

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Die Bruchzähigkeit von Fichte und ihre wesentlichen Einflußparameter

The characteristic of beams with rectangular blockouts and breakthroughs is the high stress state in the sharp notches. To estimate the bearing capacity based on theK-concept the knowledge of the fracture toughness for mode-1 (tension transverse to the grain) and for mode-2 (shear) is necessary. The fracture toughness of spruce in the mode-2 is determined by using the beam-specimen. The essential influences are the density and the orientation of the annual rings in the notch.     

Comparative chemical composition,antioxidant and hypoglycaemic activities of Juniperus oxycedrus ssp. oxycedrus L. berry and wood oils from Lebanon

Juniper (Juniperus oxycedrus) is used in European cuisine for its distinguishing flavour. J. oxycedrus ssp. oxycedrus berry and wood essential oils were tentatively identified by GC and GC/MS. Fifty compounds were identified in the berry oil and 23 compounds were identified in the wood oil. The J. oxycedrus ssp. oxycedrus berry oil was characterised by high contents of α-pinene (27.4%) and β-myrcene (18.9%). Other important compounds were α-phellandrene (7.1%), limonene (6.7%), epi-bicyclosesquiphellandrene (2.3%) and δ-cadinene (2.2%) while, in the wood oil, δ-cadinene (14.5%) is a major main component, together with cis-thujopsene (9.2%) and α-muurolene (4.9%). In vitro evaluation of antioxidant activity by the DPPH method showed a significant activity for both oils with IC₅₀ values of 1.45 μl/ml for wood and 7.42 μl/ml for berries. Hypoglycaemic activity was investigated through the inhibition of α-amylase. The results revealed that oil obtained by hydrodistillation from J. oxycedrus ssp. oxycedrus wood exhibits an interesting activity with IC₅₀ of 3.49 μl/ml.     

Fracture in spruce: experiment and numerical analysis by linear and non linear fracture mechanics

That paper first presents a simplified Damage Mechanics (DM) model for the simulation of fracture in wood. All damage phenomena are assumed to occur on a surface (or a line in a 2D problem). Then test results of mode I fracture in spruce and fir are given. The size effect is investigated. Linear Elastic Fracture Mechanics (LEFM) and DM are compared for a simulation of three point bending tests, classically used for the determination of the fracture energy (G _f) in tension perpendicular to grain. The study of the observed size effect gives the range of applicability of LEFM. The critical energy release rate (G _c) and the fracture energy (Y _f) that are energy parameters of LEFM and DM respectively, are identified for small specimens and compared with the experimentally dissipated energy to fracture the specimen (G _f). Load-displacement curves are correctly predicted with both methods. G _f can be considered as a material parameter and it is verified that a non-linear approach is necessary for the simulation of fracture of small specimens.     

Purification and identification of a ACE inhibitory peptide from oyster proteins hydrolysate and the antihypertensive effect of hydrolysate in spontaneously hypertensive rats

Oyster (Crassostrea talienwhanensis Crosse) proteins were produced from fresh oyster and subsequently digested with pepsin. The separations were performed with a Sephadex LH-20 gel filtration chromatography and a RP-HPLC. A purified peptide with sequence Val-Val-Tyr-Pro-Trp-Thr-Gln-Arg-Phe (VVYPWTQRF) was firstly isolated and characterized from oyster protein hydrolysate and its ACE inhibitory activity was determined with IC₅₀ value of 66 μmol/L in vitro. Stability study for ACE inhibitory activity showed that the isolated nonapeptide had the good heat and pH stability and strong enzyme-resistant properties against gastrointestinal proteases. Kinetic experiments demonstrated that inhibitory kinetic mechanism of this peptide was non-competitive and its K_m and K_i values were calculated. The yield of this peptide from oyster proteins was 8.5%. Furthermore, the oyster protein hydrolysate (fraction II), prepared by pepsin treatment firstly exhibited antihypertensive activity when it was orally administered to spontaneously hypertensive rat (SHR) at a dose of 20 mg/kg. These results demonstrated that the hydrolysate from oyster proteins prepared by pepsin treatment could serve as a source of peptides with antihypertensive activity.     

Composition and enzyme inhibitory properties of finger millet (Eleusine coracana L.) seed coat phenolics: Mode of inhibition of α-glucosidase and pancreatic amylase

Inhibitors of alpha glucosidase and pancreatic amylase play a vital role in the clinical management of postprandial hyperglycemia. Although, powerful synthetic inhibitors are available, natural inhibitors are potentially safer. Phenolic compounds from the millet seed coat were extracted with acidified methanol and characterised by HPLC and ESI-MS. These phenolics showed strong inhibition towards α-glucosidase and pancreatic amylase and the IC₅₀ values were 16.9 and 23.5 μg of phenolics, respectively. The enzyme kinetic studies, using Michaelis–Menton and Lineweaver–Burk equations, indicated that, in the presence of millet phenolics, the Michaelis–Menton constant (K_m) remained constant but the maximal velocity (V_max) decreased, revealing a non-competitive type of inhibition. The study indicated the therapeutic potentiality of millet phenolics in the management of postprandial hyperglycemia.     

Inhibitory effects of cinnamic acid and its derivatives on the diphenolase activity of mushroom (Agaricus bisporus) tyrosinase

The effects of cinnamic acid and its derivatives (2-hydroxycinnamic acid, 4-hydroxycinnamic acid and 4-methoxycinnamic acid) on the activity of mushroom tyrosinase have been studied. Results showed that cinnamic acid, 4-hydroxycinnamic acid and 4-methoxycinnamic acid strongly inhibited the diphenolase activity of mushroom tyrosinase and the inhibition was reversible. The IC₅₀ values were estimated to be 2.10, 0.50 and 0.42 mM, respectively. 2-Hydroxycinnamic acid had no inhibitory effect on the diphenolase activity of the enzyme. Kinetic analyses showed that the inhibition type of cinnamic acid and 4-methoxycinnamic acid was noncompetitive with the constants (K_I) determined to be 1.994 and 0.458 mM, respectively. The inhibition type of 4-hydroxycinnamic acid was competitive, with the inhibition constant (K_I) was 0.244 mM.     

Mode of pancreatic lipase inhibition activity in vitro by some flavonoids and non-flavonoid polyphenols

Numerous reports have shown plant metabolites as potential inhibitors of pancreatic lipase (PL). The most notable group is plant polyphenols. However, a limited number of reports diagnosed their mode of inhibition delineating conflicting results. To elucidate the kinetic mode of PL inhibition, some selected flavonoid and non-flavonoid polyphenol standards were first screened for their lipase inhibition potency by their half maximal inhibitory concentration (IC₅₀) followed by inhibition kinetic analysis. Of the phenolics tested, only gallic acid (GA) and galloyl moiety containing epicatechin, viz., epigallocatechin (EGC) and epigallocatechin gallate (EGCG) showed, comparative to others, higher PL inhibitions (IC₅₀, 387.2, 237.3, and 391.2 μM respectively). Analysis of enzyme inhibition modalities at various substrate concentrations revealed a dose-dependent inhibition of reaction velocity. Inhibitory rates decreased by the order of EGCG > EGC > GA (Ki, 13.29 > 35.0 > 44.61 μM respectively). The results, when verified by visual inspection of Lineweaver–Burk as well as Dixon plots, showed inhibitions of PL by GA, EGC, and EGCG that were best fit to competitive inhibitions. A role of the galloyl moiety in enzyme-inhibitor binding has been evident from their structural resemblance. Depicting it further, ethyl gallate (EG), showed a similar competitive inhibition, therefore, indicating a galloyl moiety driven competitive inhibition of PL.     

Bruchenergien,kritische Energiefreisetzungsraten und Bruchzähigkeiten von Fichte bei Zugbeanspruchung senkrecht zur Faserrichtung

It is reported on Mode I fracture energyG _f, critical strain energy release rateG _c and fracture toughnessK _c of spruce in RL-crack system. The investigations were performed with special SENB specimens acc. to a CIB W18A draft standard. For determination of size effects geometrically similar specimens of significant different sizes were tested; the cross-sectional depthd varied from 10 to 320 mm and notch length was constant 0,6d. All “tension perpendicular to grain volumes” were cut from two boards with similar mean densities of about 460 kg/m³. The paper first deals with some general aspects of related energy termsG _f resp.G _c and then gives finite element results for normalized strain energy release rates and stress intensity factors of the specific orthotropic specimen. The experimental results can be summarized as follows: Fracture energyG _f is quite independent of initial crack length and counts in mean 280 N/m; the 5th percentile value due to fitted 3parameter Weibull distribution is 180 N/m and thus about 30% lower as given implicitly in Eurocode 5 for respective density. For density dependency in the range of about 420 to 480 kg/m³ the linear relationG _f≈0,62 ρ₁₂ was found. Critical strain energy release rateG _c increases degressively with specimen depth resp. initial crack length. Compared toG _f,G _c is roughly 25% lower up to crack lengths of about 60 mm and is then of similar quantity asG _f. Fracture toughnessK _c alikeG _f, was found to be quite independent of initial crack length; for mean and characteristic values 440 resp. 280 kN/√m³ were received.     

Purification and characterisation of angiotensin I converting enzyme inhibitory peptides from lysozyme hydrolysates

Hen egg white lysozyme (HEWL) was hydrolysed with trypsin, papain and a combination of the two. The prepared hydrolysates exhibited ACE inhibitory activity. The hydrolysates were fractionated using ultrafiltration and reverse phase-high performance liquid chromatography (RP-HPLC). Three fractions, which showed the highest ACE inhibitory activities, were purified by RP-HPLC. They were the F₇ (from papain-trypsin hydrolysate), F₈ (from papain hydrolysate) and F₃ (from trypsin hydrolysate) fractions. The IC₅₀ values were 0.03, 0.155 and 0.23 mg/ml for F₇, F₈ and F₃, respectively. The F₇ fraction was the most potent ACE inhibitor peptide, and was composed of 12 amino acids, Phe-Glu-Ser-Asn-Phe-Asn-Thr-Gln-Ala-Thr-Asn-Arg (MW: 1428.6 Da). Lineweaver-Burk plots suggest that the F₇ peptide acts as an uncompetitive inhibitor against ACE. The kinetic parameters (K_m, V_max, and K_i) for the F₇ peptide were measured and compared to the control.     

Isolation and characterisation of an α-glucosidase inhibitory substance from fructose–tyrosine Maillard reaction products

An α-glucosidase inhibitory substance was isolated and characterised from fructose–tyrosine Maillard reaction products (MRPs) and the inhibition mode of the active substance determined. The ethyl acetate fraction of fructose–tyrosine MRPs showed strong α-glucosidase inhibitory activity; this fraction was isolated and purified using silica gel column chromatography and semi-preparative RP-HPLC. The structure of the purified compound was determined using spectroscopic methods. The isolated compound was identified as 2,4-bis (p-hydroxyphenyl)-2-butenal (C₁₆H₁₄O₃, HPB242). This is the first report of baker’s yeast α-glucosidase inhibitory activity of HPB242 isolated from fructose–tyrosine MRPs. The IC₅₀ value of HPB242 on α-glucosidase inhibition was 4.00 ± 0.09 μg/ml. Kinetic data revealed that HPB242 inhibits the p-NPG hydrolysing activity of baker’s yeast α-glucosidase noncompetitively with a K_i value of 0.870 mM.     

UPLC-ESI-MS/MS for determining trans- and cis-vitamin K1 in infant formulas: method and applications

A simple and sensitive method of determining vitamin K₁ isomers (cis-and trans-forms) was developed for routine monitoring of supplemented infant formulas. The proposed method involves the applications of the lipase hydrolysis and the liquid-to-liquid extraction. After the hydrolysis and extraction procedures, the vitamin K₁-enriched extract was directly injected into the ultra-performance liquid chromatography–tandem mass spectrometry system (UPLC-MS/MS). The components were detected using electrospray ionization (ESI) in positive-ion and quantified by multiple-reaction monitoring (MRM) mode. trans-vitamin K₁ was separated from the biologically inactive cis-isomer through a C₃₀ column (4.6?×?150?mm, 3?μm), and vitamin K₁-d₇ was used as an internal standard. Calibration curves were linear over the range of 9.3–464.75?ng?ml^?1 for trans-vitamin K₁ (r ²?>?0.999) and 1.71–85.25?ng?ml^?1 for cis-vitamin K₁ (r ²?>?0.999). The limit of detection for trans- and cis-vitamin K₁ was 0.011?μg 100?g^?1 and 0.01?μg 100?g^?1. The limit of quantification was 0.037?μg 100?g^?1 and 0.031?μg 100?g^?1, respectively. The intra- and inter-batch variations (RSD%) were less than 5?%. The proposed method was applied to determine vitamin K₁ isomers in milk-based, soy-based and rice-based infant formulas, and the cis-vitamin K₁ isomer contributes to 7.05–17.21?% of the total vitamin K₁ in certain infant formulas.     

Changes in fatty acid composition in muscle and adipose tissue of farmed rainbow trout (Oncorhynchus mykiss) in relation to ration and age

To evaluate the importance of age and feed ration level (RL) on the composition of tissue fatty acid (FA) in rainbow trout (Oncorhynchus mykiss), fish were fed rations ranging from appreciable underfeeding to gross overfeeding in a longitudinal experiment lasting from start of feeding to onset of sexual maturation 2.4 years later. In order to study the effects of compensatory growth and reduced feed availability, fish were moved from high to low ration and vice versa. Changes of individual FA of total lipid (TL), triacylglycerols (TAG) and total phospholipids (PL) were studied in white and red muscle, as well as in three major adipose tissues. The effect of saltwater transfer on FA composition was also examined. A strong interdependence was found between the relative proportion of PL and TAG with changes in TL content. This was most prominent in white muscle. In parallel with this change in relative lipid class composition, a major effect was seen on FA in the TL fraction. The most marked effect of RL was an inverse relationship between 22:6 n-3 of the PUFA n-3 series and 16:1 and 18:1 of the MUFA series. This was seen in all tissues studied. It is suggested that the most important factor governing FA composition in muscle, pending changes in feed intake, is the TL content, affecting the relative level of PL and TAG. In adipose tissue, consisting mainly of TAG, more subtle changes were observed. The FA compositions of PL and TAG were not affected to any major extent by RL, except at extreme reductions. Significant changes in FA of PL and TAG were observed as an effect of saltwater transfer.     

Activities and sequences of the angiotensin I‐converting enzyme (ACE) inhibitory peptides obtained from the digested lentil (Lens culinaris) globulins

The aim of this study was the identification of potentially bioaccessible ACE‐inhibitory peptides obtained by in vitro gastrointestinal digestion of lentil globulins. ACE‐inhibitory peptides were purified by ion exchange chromatography and gel filtration. After the first step of purification, three peptide fractions with potential antihypertensive properties were obtained and the highest inhibitory activity was determined for the fraction 5 (IC₅₀ = 0.02 mg mL^?1). This fraction was separated on Sephadex G10, and six peptide fractions were obtained. The peptides of fraction (5‐F) with the highest potential antihypertensive activity (IC₅₀ = 0.13 mg mL^?1) were identified using ESI‐MS/MS. The sequences of peptides were KLRT, TLHGMV and VNRLM. Based on Lineweaver–Burk plots for the fraction 5‐F, the kinetic parameters as K_m (1.24 mm ), V_max (0.012 U min^?1), K_i (0.12 mg mL^?1) and mode of inhibition were determined.     

Applicability of thermoluminescence techniques to identify irradiated seafoods using different methods of mineral separation: An interlaboratory blind trial

Thermoluminescence (TL) technique for identifying γ-irradiated (0–10 kGy) anchovies (dried), kelp (dried), and mackerel (fresh) was validated in an interlaboratory blind trial. Different irradiation detection laboratories were involved by using 2 methods of mineral separation (density separation and acid hydrolysis) for the analysis. Key TL parameters, including the TL glow-curve shape, intensity, and the TL ratio (TL₁/TL₂) were used to characterize the irradiation status. All irradiated samples exhibited an intense TL peak at approximately 200°C, which was absent in non-irradiated samples. TL glow curve interpretations were also confirmed by determining the TL ratio. Different participating laboratories reported 89–100% correct results. Both methods of mineral separation were equally effective; however, some variation was observed in the results from different laboratories for irradiated mackerel, which might be due to a lack of isolated minerals, differences in personnel expertise, and different TL instruments.     

Mechanism for the inhibition of apple juice enzymatic browning by Palo Fierro (desert ironweed) honey extract and other natural compounds

Inhibition of Red Delicious apple juice browning and apple polyphenoloxidase (PPO) activity by four natural anti-browning agents [palo fierro honey extract (PFH), caffeic acid phenethyl ester (CAPE), l-cysteine (Cys), and 4-hexylresorcinol (4HR)] has been studied. Browning of apple juice was markedly reduced by 4HR, Cys, and PFH, however, little effect was observed with CAPE. PFH, CAPE, and 4HR showed high inhibition of apple juice PPO. When the inhibition mechanism of these compounds over partially purified apple PPO was studied using chlorogenic acid as substrate, PFH acted as a noncompetitive inhibitor of apple PPO, with K_i = αK = 0.8 g/L, and IC₅₀ ranging 1.1-1.7 g/L. Cys showed an inhibitory pattern which could not be fitted to any type of reversible inhibition (IC₅₀ 0.02-0.03 g/L), while CAPE showed low inhibitory activity, which could be due to co-precipitation processes. PFH could be considered as an effective natural compound to reduce apple juice browning.     

On the influence of crack closure on strength estimates of wood

Three well-known duration of load models (Gerhard, Barrett/Foschi, DVM) are considered in this note with respect to their ability to predict lifetime of wood subjected to harmonically varying loads. The result obtained is that they practically predict the same lifetime—which for low frequency loading can be considered approximately true. For higher frequencies, however, this result can be far too overestimated. The reason is that the models considered do not take into account the effect of the crack closure phenomenon (which are the main mechanisms of energy dissipation causing fatigue failure in metals). It is suggested that any of the simple models can be used in practice when low frequency load variations are considered. The DVM model, however, should be preferred because of its ability to predict residual strength, and because of its ‘build in’ flexibility with respect to wood quality and ambient climatic conditions. For high frequency load histories more refined models are required. The extended DVM model, recently developed by the author, is suggested as such a model—especially because it has the potentials of being further developed to consider arbitrary load variations (such as earthquakes). Finally, the widely spread concept of estimating long-term strength by multiplying short time strength with a codified factor (so-called k _MOD factor) is discussed. It is concluded that the k _MOD -method can be justified in practice with low frequency load variations. When high frequency load histories or unexpected peak loads are considered, the k _MOD -method may cause considerably overestimated lifetimes.     

Discovering Bisdemethoxycurcumin from Curcuma longa rhizome as a potent small molecule inhibitor of human pancreatic α-amylase,a target for type-2 diabetes

Curcuma longa rhizome is used extensively in culinary preparations in Far East and South-East Asia. Health benefits of curcuminoids from C. longa as antioxidants, anti-cancer and anti-inflammatory molecules have been well documented. We report here for the first time that Bisdemethoxycurcumin (BDMC) from C. longa, acts as an inhibitor to inactivate human pancreatic α-amylase, a therapeutic target for oral hypoglycemic agents in type-2 diabetes. Bioactivity guided isolation of rhizome isopropanol extract led to the identification by HPLC and NMR of BDMC as a lead small molecule inhibitor of porcine and human pancreatic α-amylase with an IC₅₀ value of 0.026 and 0.025 mM, respectively. Kinetic analysis revealed that using starch as the substrate, HPA exhibited an uncompetitive mode of inhibition with an apparent K_i of 3.0 μM. The study gains importance as BDMC could be a good drug candidate in development of new inhibitors of HPA and of functional foods for controlling starch digestion in order to reduce post-prandial hyperglycemia.     

Sekundäre Veränderungen im Holz akut belasteter Fichten (Picea abies [L.] Karst.) in Hochlagen des Osterzgebirges

Within the framework of an interdisciplinary research project “investigation of forest ecosystems in the ore-mountains as basis for an ecologically oriented silviculture” supported by the Federal-ministry for education, science, research and technology (BMBF), Bonn, a study of the wood quality of heavily SO₂-polluted and wind-exposed spruce trees from high altitude stands was conducted. For this study wood from 6 standing, wind-exposed and 6 storm-tossed trees with brash fractures was considered. By means of light microscopy (polarization, phase contrast) and electron microscopy the formation, distribution and extension of slip planes within the cell walls were examined and their significance for fracture initialization quantified. Wood discolouring and wood destroying fungi were isolated from the fracture zones and taxonomically determined. The extent of wood decay was characterized on a cellular and subcellular scale by means of fluorescence microscopy and UV spectroscopy. In the heavily SO₂-polluted and thinned-out spruce stands at the high altitudes of the ore-mountains extreme wind stresses initiate in some tress slip planes which accumulate in the vicinity of rays and branch tracers. The slip plane zones are subsequently infected by wood degrading fungi, in particular by Stereum sanguinolentum (Alb. et Schw.: Fr.) Fr. resulting in a simultaneous decay of carbohydrates and lignin in the cell walls. The combined effect of wind stress and cell-wall degradation apparently induces brash, staircase-like fractures in some stems, which limitates the utilization of the timber. Eventually reduced SO₂ immissions and an improved stand structure will help avert this kind of damage and spruce grown at this site will again satisfy standard wood quality requirements.     

Nichtlineares Bruchmechanik-Maßstabsgesetz für Fichte bei Zugbeanspruchung senkrecht zur Faserrichtung

A report is given on investigations, concerning fracture mechanics based size effect of clear spruce wood loaded in mode I in RL-crack system. The tests were performed with single notched, geometrically almost 2D-similar SENB bending specimens. The beam depths,d, varied from 10 to 320 mm, the notch lengths were constant 0,6 timesd. The entity of test results could be approximized well by means of a steady nonlinear fracture mechanics size effect law by Bazant, whereas the Weibull weak link hypothesis, according to fracture mechanics based failure, is rather inapt. The received size effect conformed nearly exactly to the size effect law of linear fracture mechanics (LEFM) with the larger pecimens (d≥160mm). Along with, increasingly smaller sizes a reduced size effect was abtained agreeing well with assumptions of nonlinear fracture mechanics (NLFM), i.e. growing influence of softening fracture prozess zone. The experimental transition region between NLFM and LEFM can be specified via brittleness number β～10, a fracture mechanics parameter independent of individual test configuration.