Determination and Separation of Diarylheptanoids From Alder Growing in Latvia

The composition of diarylhepatnoids fraction isolated from bark of two alder species (grey alder and black alder) was studied. The efficiency of three extraction methods used for isolation of diarylhepatnoids from alder bark was compared. Two diarylhepatnoids: 1,7-bis-(3,4-dihydroxyphenyl)-heptan- 3-one-5-O-β-D-xylopyronoside (oregonin) and 1,7-bis-(3,4-dihydroxyphenyl)-3-hydroxyheptane-5-O-β-D- xylopyranoside were isolated from the bark of grey alder. The phenolic components of the extracts were analyzed by high-performance liquid chromatography (HPLC). Quantitative determination of oregonin was performed using an internal standard method. The results obtained show that alder barks are rich source of diarylhepatnoids

Sea Buckthorn (Hippophae rhamnoides) Waste Biomass after Harvesting as a Source of Valuable Biologically Active Compounds with Nutraceutical and Antibacterial Potential

Funding Information: Funding: This research was funded by ERDF project nr. Nr.1.1.1.1/19/A/146 “Biorefinery processing of sea buckthorn non-fruit biomass using innovative techniques and comprehensive analytical investigation, for obtaining prospective for Latvian bioeconomy high value-added products, including serotonin”. Publisher Copyright: © 2022 by the authors. Licensee MDPI, Basel, Switzerland.For sustainable sea buckthorn (Hippophae rhamnoides) berry production, the task at hand is to find an application for the large amount of biomass waste arising at harvesting. Sea buckthorn (SBT) vegetation is currently poorly studied. The purpose of this research was to assess the composition and potential of SBT twigs as a source of valuable biologically active substances. Water and 50% EtOH extracts of twigs of three Latvian SBT cultivars with a high berry yield and quality, popular for cultivation in many countries (H. rhamnoides ‘Maria Bruvele', ‘Tatiana', ‘Botanicheskaya Lubitelskaya'), were investigated for the first time. The phytochemical composition (UHPLC-ESI-MS/MS analysis) and biological activity of the obtained hydrophilic extracts were determined. The highest yield of polyphenolic compounds and serotonin was observed for ‘Maria Bruvele'. Hydrophilic extracts were investigated for radical scavenging activity (DPPH' test), antibacterial/antifungal activity against five pathogenic bacteria/yeast, cytotoxicity, and the enzymatic activity of alpha-amylase (via in vitro testing), which is extremely important for the treatment of people with underweight, wasting, and malabsorption. The results showed a high potential of sea buckthorn biomass as a source of valuable biologically active compounds for the creation of preparations for the food industry, nutraceuticals, and cosmetics.publishersversionPeer reviewe

Changes of humic substances chemical characteristics during composting of lignocellulosics and lignocellulosic/animal grease waste mixture

Elektroniskā versija nesatur pielikumusPromocijas darbā tika veikta atkritumu gaļas tauku kompostēšana kopā ar lapkoku mehāniskās apstrādes atkritumiem un zāli, un iegūts kvalitatīvs komposts. Atkritumu tauki ātri sadalās un neietekmē komposta humusvielu sastāvu. Izpētīta Bjorkmana lignīna un humusvielu, kas izdalīti no modeļa zāles komposta, ķīmiskais sastāvs un to izmaiņas kompostēšanas laikā. Pētāmā komposta humusvielas satur ievērojamu daudzumu izmainītu lignīna fragmentu. Kombinējot ozonēšanu, nitrobenzola oksidēšanu un metoksilgrupu analīzes rezultātus pierādīts, ka kompostēšanas laikā notiek lignīna demetoksilēšana, lignīna struktūras kondensēšana, un visstraujāk lignīna alifātiskās ķēdes oksidatīvā šķelšanās. Alifātiskās ķēdes šķelšanas mērījumi var tikt izmantots kā viens no komposta kvalitātes rādītājiem, īpaši fulvoskābju frakcijā. Komposta humusvielu spēja pildīt barjerfunkcijas lomu metālisko jonu migrācijā un samazināt to toksiskumu pierādīta laboratorijas apstākļos. Modificējot kompostu ar Si savienojumiemThe promotional work is devoted to composting of meat grease waste with hardwood mechanical processing by-products and well as grass. The grease waste rapidly decomposes and does not influence the compost quality. The chemical composition and its changes during composting were evaluated for BjĻrkman lignin and humic substances separated from the model grass compost during composting. The compost humic substances under study contain a considerable amount of lignin components with an altered structure. Combining the results of ozonation, nitrobenzene oxidation and methoxyl groups analysis, it has been testified that, during composting, lignin demetoxylation, lignin structure condensation, and most rapid oxidative cleavage of lignin aliphatic chains occur. Measurement of aliphatic chains’ cleavage can be used as one of compost quality indices, especially for the fulvic acid fraction. Compost humic substances can play a barrier role in metal ions migration and decrease their toxicity. Mo

Komposta humusvielu ķīmiskais raksturojums un to izmaiņas lignocelulozes un lignocelulozes/gaļas tauku atkritumu kompostēšanas gaitā

Promocijas darbā tika veikta atkritumu gaļas tauku kompostēšana kopā ar lapkoku mehāniskās apstrādes atkritumiem un zāli, un iegūts kvalitatīvs komposts. Atkritumu tauki ātri sadalās un neietekmē komposta humusvielu sastāvu. Izpētīta Bjorkmana lignīna un humusvielu, kas izdalīti no modeļa zāles komposta, ķīmiskais sastāvs un to izmaiņas kompostēšanas laikā. Pētāmā komposta humusvielas satur ievērojamu daudzumu izmainītu lignīna fragmentu. Kombinējot ozonēšanu, nitrobenzola oksidēšanu un metoksilgrupu analīzes rezultātus pierādīts, ka kompostēšanas laikā notiek lignīna demetoksilēšana, lignīna struktūras kondensēšana, un visstraujāk lignīna alifātiskās ķēdes oksidatīvā šķelšanās. Alifātiskās ķēdes šķelšanas mērījumi var tikt izmantots kā viens no komposta kvalitātes rādītājiem, īpaši fulvoskābju frakcijā. Komposta humusvielu spēja pildīt barjerfunkcijas lomu metālisko jonu migrācijā un samazināt to toksiskumu pierādīta laboratorijas apstākļos. Modificējot kompostu ar Si savienojumiemThe promotional work is devoted to composting of meat grease waste with hardwood mechanical processing by-products and well as grass. The grease waste rapidly decomposes and does not influence the compost quality. The chemical composition and its changes during composting were evaluated for BjĻrkman lignin and humic substances separated from the model grass compost during composting. The compost humic substances under study contain a considerable amount of lignin components with an altered structure. Combining the results of ozonation, nitrobenzene oxidation and methoxyl groups analysis, it has been testified that, during composting, lignin demetoxylation, lignin structure condensation, and most rapid oxidative cleavage of lignin aliphatic chains occur. Measurement of aliphatic chains’ cleavage can be used as one of compost quality indices, especially for the fulvic acid fraction. Compost humic substances can play a barrier role in metal ions migration and decrease their toxicity. Mo

Influence of Manufacturing Conditions on Binder-Less Boards from Steam-Exploded Hemp Shives and Wheat Straw

In the current decade, based on the European Green Deal, new challenges of the wood-based panel industry have arisen, seeking for formaldehyde-free bio-based adhesives and broadening raw lignocellulosics. In order to contribute to the potential solution to the challenges, binder-less boards of steam-exploded (SE 220 °C/2 min) hemp shives and wheat straw were investigated. The objective of this study was to find out the optimal hot-pressing conditions in terms of temperature (150–200 °C) and time (5–16 min) for the boards with three density levels (800–1000–1200 kg·m−3). An experimental design was created and the influence of the variables on binder-less panels were evaluated using a randomized central composite design of the response surface methodology. Water absorption (WA) and thickness swelling (TS) during 24 h, modulus of elasticity (MOE), and modulus of rupture (MOR) in bending test, internal bonding (IB), and Fourier-transform infrared spectroscopy were determined for the obtained boards. Each detected physical-mechanical property of the obtained boards was described by statistical models being different at each density level. The optimal conditions of the obtained binder-less boards were different depending on the raw material and density. For example, the optimal conditions of the boards from SE wheat straw with a density of 800 kg m−3 were found at T = 220 °C and t = 15 min, with the achieved properties of WA = 53%, TS = 4%, MOE = 2750 N mm−2, MOR = 15.5 N mm−2, and IB = 0.64 N mm−2. Based on the achieved properties at the optimal conditions, the boards meet the requirements of the conventional particleboard Type P3 according to EN 312

Potentials of Technical Lignins for Application as Soil Amendments: Free Radical Scavengers and Biological Activity

The role of antioxidants in human and animal physiology and healthcare has been good recognized owing to studies carried out for at least 50 years. In recent years, research into antioxidant properties of naturally occurring polyphenols has drawn increasing attention. In plants and soil biology impact of reactive free radicals, in particular reactive oxygen species, and the antioxidants that control them, is the subject of much recent researches aimed at understanding of mechanisms of the processes involved in soil organic matters (SOM) dynamics and of the chemical stabilization of SOM in particular. Lignins isolated from plant tissue, so called technical lignins – co-products of wood and agricultural plants chemical processing are intensively investigated as antioxidants for various materials. The main objective of this study was to investigate the radical scavenging activity of the 12 lignin preparations obtained by alkaline delignification of deciduous and coniferous wood species, agricultural plants and waste from their processing, identifying the structural features of the lignin most important for its antiradical efficiency and to search relationship between lignin antioxidant and biological activities. Rutin, epicatechin and ethanol extract from bee propolis were tested in order to assess the efficacy of lignin preparations as antioxidants. Antimicrobial effects of lignin preparations were tested using 24 isolates of soil Gram negative bacteria and 1 yeast culture. Among the technical lignins studied the highest antioxidant efficacy close to that for some plant flavonoids, applied as antioxidants in medicine and veterinary, was detected for the lignins obtained from aspen and flax. These samples could be considered as prospective polymeric antioxidants of natural origin, able to compete with low-molecular commercialized antioxidants. The antioxidant properties of technical lignins highlight their good potentials for application in the „soil-plant” system

Design of Adhesive Joints with Different Elastic Properties

Design of adhesive joints with different elastic propertie

Investigation on fracture of epoxy-filled composites by acoustic emission

Acoustic emission (AE) technique is widely used to monitor failure processes in composite materials includ-ing development of cracks and plastic deformations within the polymer matrix, fracture and debonding of inclusions, etc. In this study, the AE technique was applied investigating failure character of epoxy polymers with different content of nanofiller – fine polyethersulfone (PES) powder. Variation of material properties of the epoxy with 0, 5%, 7.5%, 10%, and 12.5% concentration (by weight) of the PES was assessed experimentally. Correlation between the PES content and the modulus of elasticity was found negligible. The same was characteristic for the tensile strength. Whereas, such a correlation was found significant for the fracture toughness that increased 1.5 times concerning the pure epoxy reference. Analysis of the cumulative AE counts indicated existence of three different stages of the damage accumulation process, which were unidentified using the load and the deformation diagrams. In the PES-modified composites, the damage ac-cumulation process was evidenced at the 10–20% of the ultimate load; whereas, in the pure epoxy, such a process was fairly slow until the 85% of the loading

Development of the approaches for complex utilization of brown algae (Fucus vesiculosus) biomass for the obtaining of value-added products

The seaweed collected after stranding on beaches of Latvia is underexploited natural resource, which has a potential as raw material for biologically active compound extraction for cosmetic and pharmacy and fertilizer in sustainable agriculture. The aim of the present study was development of the approach for the processing of brown alga Fucus vesiculosus biomass, collected from the Gulf of Riga. The thorough characterization of the chemical composition of Fucus vesiculosus has shown that it is a potential source for obtaining of nitrogen-containing fertilizers, and biologically active compounds. One of the proposed approaches for the processing of the Fucus vesiculosus biomass under study includes algae extraction with organic solvents and CaCl2 solution and obtaining soil organic amendment on the basis of the extract-free residue. The ethyl acetate extract was rich in phenolic compounds (430 ± 30 GAE mg/g) with high antioxidant activity in DPPH• and ABTS•+ tests. The ethanol extract contained significant amounts of phlorotannins that was confirmed by the data of LC-MS/MS analysis. The CaCl2 extract was used for the obtaining of sulphated polysaccharide fucoidane (yield ≈7% on the basis of oven dry matter, o.d.m.), which has numerous biological activities. The extract-free residue didn’t show phytotoxicity. The extract free algal biomass exhibited positive effect in root elongation tests with oat (Avena sativa). As alternative approach for processing of the algal biomass, the mechano-chemical treatment of algal biomass with lignin was proposed. EPR analyses confirmed interaction between algal biomass and lignin

Characterization of Softwood and Hardwood LignoBoost Kraft Lignins with Emphasis on their Antioxidant Activity

Fractionation of softwood and hardwood LignoBoost kraft lignins, using sequential extraction with organic solvents of increasing hydrogen-bonding ability (dichloromethane, n-propanol, and methanol), was carried out. Using SEC, analytical pyrolysis, FTIR and UV/VIS spectroscopy, and chemical analytical methods, four fractions were obtained and characterized in terms of their yield, composition, functionality, lignin structural features, and antioxidant properties. In tests with free radicals (ABTS●+, DPPH●, O2●-) and the ORAC (oxygen radical absorbance capacity) assay, the high radical scavenging capacity of the lignin’s soluble fractions was demonstrated. The antioxidant activity of the fractions was tested by their influence on thermo-oxidative destruction of model polyurethane elastomers. The TGA data clearly revealed the antioxidant effect of the three fractions, with the most prominent activity for the propanol-soluble fraction. The dichloromethane fraction has potential as an antioxidant for non-polar products. Novel correlations between lignin’s structural features and its radical scavenging activity were found that can be used for tuning lignin’s antioxidant properties