Antioxidant Activity of Different Extracts from Black Alder (Alnus glutinosa) Bark with Greener Extraction Alternative

Extraction and Biological Activity of Lignanoids from Magnolia officinalis Rehder & E.H.Wilson Residual Waste Biomass Using Deep Eutectic Solvents

Lignanoids are an active ingredient exerting powerful antioxidant and anti-inflammatory effects in the treatment of many diseases. In order to improve the efficiency of the resource utilization of traditional Chinese medicine waste, Magnolia officinalis Rehder & E.H.Wilson residue (MOR) waste biomass was used as raw material in this study, and a series of deep eutectic solvents (ChUre, ChAce, ChPro, ChCit, ChOxa, ChMal, ChLac, ChLev, ChGly and ChEG) were selected to evaluate the extraction efficiency of lignanoids from MORs. The results showed that the best conditions for lignanoid extraction were a liquid-solid ratio of 40.50 mL/g, an HBD-HBA ratio of 2.06, a water percentage of 29.3%, an extract temperature of 337.65 K, and a time of 107 min. Under these conditions, the maximum lignanoid amount was 39.18 mg/g. In addition, the kinetics of the extraction process were investigated by mathematic modeling. In our antioxidant activity study, high antioxidant activity of the lignanoid extract was shown in scavenging four different types of free radicals (DPPH, ·OH, ABTS, and superoxide anions). At a concentration of 3 mg/mL, the total antioxidant capacity of the lignanoid extract was 1.795 U/mL, which was equal to 0.12 mg/mL of Vc solution. Furthermore, the antibacterial activity study found that the lignanoid extract exhibited good antibacterial effects against six tested pathogens. Among them, Staphylococcus aureus exerted the strongest antibacterial activity. Eventually, the correlation of the lignanoid extract with the biological activity and physicochemical properties of DESs is described using a heatmap, along with the evaluation of the in vitro hypoglycemic, in vitro hypolipidemic, immunomodulatory, and anti-inflammatory activity of the lignanoid extract. These findings can provide a theoretical foundation for the extraction of high-value components from waste biomass by deep eutectic solvents, as well as highlighting its specific significance in natural product development and utilization.

Seasonal Variation in Plant Polyphenols and Related Bioactivities across Three Years in Ten Tree Species as Visualized by Mass Spectrometric Fingerprint Mapping

The currently changing climates and environments place plants under many types of stresses that affect both their survival and levels of chemical defenses. The gradual induction of defenses in stressed plant populations could be monitored on a yearly basis unless a seasonal and yearly variation in natural defense levels obscures such monitoring schemes. Here, we studied the stability of the species-specific polyphenol composition and content of 10 tree species over three growing seasons using five replicate trees per species. We specifically measured hydrolyzable tannins (galloyl and hexahydroxydiphenoyl derivatives), proanthocyanidins (procyanidins and prodelphinidins), flavonols (kaempferol, quercetin and kaempferol derivatives) and quinic acid derivatives with the group-specific UHPLC-DAD-MS/MS tool, together with two bioactivities, the protein precipitation capacity and oxidative activity. With the help of a fingerprint mapping tool, we found out that species differed a lot in their seasonal and between-year variation in polyphenols and that the variation was also partially specific to compound groups. Especially ellagitannins tended to have declining seasonal patterns while the opposite was true for proanthocyanidins. Some of the species showed minimal variation in all measured variables, while others showed even induced levels of certain polyphenol groups during the 3-year study. For every species, we found either species-specific baseline levels in qualitative and quantitative polyphenol chemistry or the compound groups with the most plasticity in their production. The used tools could thus form a good combination for future studies attempting to monitor the overall changes in polyphenol chemistry due to various biotic or abiotic stress factors in plant populations or in more controlled environments.

Spent Coffee Grounds Valorization in Biorefinery Context to Obtain Valuable Products Using Different Extraction Approaches and Solvents

The valuable products that can be isolated from spent coffee ground (SCG) biomass consist of a high number of bioactive components, which are suitable for further application as raw materials in various production chains. This paper presents the potential value of the SCG obtained from large and local coffee beverage producers, for the production of valuable, biologically active products. Despite its high potential, SCG has not been utilized to its full potential value, but is instead discarded as waste in landfills. During its decomposition, SCG emits a large amount of CO₂ and methane each year. The main novelty of our work is the implementation of sequential extraction with solvents of increased polarity that allows for the maximal removal of the available extractives. In addition, we have compared different extraction techniques, such as conventional and Soxhlet extraction, with more effective accelerated solvent extraction (ASE), which has seen relatively little use in terms of SCG extraction. By comparing these extraction methods and highlighting the key differences between them in terms of extraction yield and obtained extract composition, this work offers key insights for further SCG utilization. By using sequential and one-step accelerated solvent extraction, it is possible to obtain a significant number of extractives from SCG, with a yield above 20% of the starting biomass. The highest yield is for coffee oil, which is obtained with n-hexane ranging between 12% and 14% using accelerated solvent extraction (ASE) according to the scheme: n-hexane→ethyl acetate→60% ethanol. Using single-stage extraction, increasing the ethanol concentration also increases the total phenolic content (TPC) and it ranges between 18.7-23.9 Gallic acid equivalent (GAE) mg/g. The iodine values in the range of 164-174 using ASE and Soxhlet extraction shows that the hexane extracts contain a significant amount of unsaturated fatty acids; coffee oils with a low acid number, in the range of 4.74-6.93, contain few free fatty acids. The characterization of separated coffee oil has shown that it mainly consists of linoleic acid, oleic acid, palmitic acid, stearic acid and a small number of phenolic-type compounds.

New Insights on Phytochemical Features and Biological Properties of Alnus glutinosa Stem Bark

Alnus glutinosa (namely black alder or European alder) is a tree of the Betulaceae family widely spread through Europe, Southeastern Asia, the Caucasus mountains, and Western Siberia. Its bark is traditionally used for medicinal purposes as an astringent, cathartic, febrifuge, emetic, hemostatic, and tonic, suggesting that it may contain bioactive compounds useful to counteract inflammation. The aim of this study was to investigate the phytochemical profile of A. glutinosa stem bark extract (AGE) by LC-DAD-ESI-MS/MS analysis and to validate some biological activities such as antioxidant, anti-inflammatory and anti-angiogenic properties by in vitro and in vivo models (chick chorioallantoic membranes and zebrafish embryos), that can justify its use against inflammatory-based diseases. The AGE showed a high total phenols content expressed as gallic acid equivalents (0.71 g GAE/g of AGE). Diarylheptanoids have been identified as the predominant compounds (0.65 g/g of AGE) with oregonin, which alone constitutes 74.67% of the AGE. The AGE showed a strong and concentration-dependent antioxidant (IC₅₀ 0.15–12.21 µg/mL) and anti-inflammatory (IC₅₀ 5.47–12.97 µg/mL) activity. Furthermore, it showed promising anti-angiogenic activity, inhibiting both the vessel growth (IC₅₀ 23.39 µg/egg) and the release of an endogenous phosphatase alkaline enzyme (IC₅₀ 44.24 µg/embryo). In conclusion, AGE is a promising source of antioxidant, anti-inflammatory and angio-modulator compounds.

Study of the Antioxidant Properties of Filipendula ulmaria and Alnus glutinosa

The demographic situation of the last few decades is characterized by the increased numbers of elderly and senile people, i.e., by the aging of the population. In humans, ageing is closely associated with the enhanced production of reactive oxygen species (ROS), development of systemic inflammation and related vascular atherosclerotic alterations and metabolic disorders, like obesity, diabetes mellitus and neurodegenerative diseases. As these age-related alterations are directly associated with up-regulation of ROS production and development of chronic oxidative stress, their onset can be essentially delayed by continuous daily consumption of dietary antioxidants-natural products of plant origin. Such antioxidants (in the form of plant extracts, biologically active complexes or individual compounds) can be supplemented to functional foods, i.e., dietary supplementations for daily diet aiming prolongation of active life and delay of the senescence onset. Thereby, use of widely spread medicinal plants might essentially improve cost efficiency of this strategy and availability of antioxidant-rich functional foods. Therefore, here we addressed, to the best of our knowledge for the first time, the antioxidant activity of the extracts prepared from the aerial parts of Filipendula ulmaria and Alnus glutinosa growing in the Kaliningrad region of Russia, and assessed the contents of the biologically active substances underlying these properties. It was found that the extract prepared with the leaves of Filipendula ulmaria and female catkins of Alnus glutinosa demonstrated high antioxidant activity, although the former plant was featured with a higher antioxidant potential. The highest antioxidant activity detected in the methanol extracts of Alnus glutinosa reached 1094.02 ± 14.53 µmol TE/g, radical scavenging of activity was 584.45 ± 35.3 µmol TE/g, reducing capacity at interaction with iron complex-471.63 ± 7.06 µmol TE/g. For the methanol extracts of Filipendula ulmaria the antioxidant activity reached 759.78 ± 19.08 µmol TE/g, antioxidant activity for free radical removal was 451.08 ± 24.45 µmol TE/g and antioxidant activity for restorative ability with iron complex was 332.28 ± 10.93 µmol TE/g. These values are consistent with the total yields of the extracts and their content of ellagic acid. The ethyl acetate extracts of the both plants showed just minimal antioxidant activity. Thus, the considered extracts have an essential potential. This creates good prospects for the further use of herbal extracts of Filipendula ulmaria and Alnus glutinosa as a source of natural antioxidants.

Microwave-Assisted Water Extraction of Aspen (Populus tremula) and Pine (Pinus sylvestris L.) Barks as a Tool for Their Valorization

The barks of aspen (Populus tremula) and pine (Pinus sylvestris) are byproducts of wood processing, characterized by their low economic value. In the present study, microwave-assisted one-cycle water extraction was explored as a tool for the valorization of this biomass as a source of biologically active compounds. The microwave extractor of the original construction equipped with a pressurized extraction chamber and a condenser section was used. The microwave-assisted extraction (MAE), specially including dynamic dielectric heating up to 70 °C followed by 30 min of isothermal heating, promoted the isolation of salicin from aspen bark, allowing for the obtention of a two-times-higher free salicin concentration in water extracts (−14% vs. 7%) reached by multi-cycle accelerated solvent extraction (ASE), which is an advanced technique used as a reference. The MAE of pine bark with dynamic heating up to 90–130 °C, avoiding the isothermal heating step, allowed for the obtention of a 1.7-times-higher concentration of proantocyanidin dimers-tetramers, a 1.3-times-higher concentration of catechin and a 1.2-times-higher concentration of quinic acid in water extracts in comparison to a more time- and solvent-consuming ASE performed at the same temperature. The biological activity of the obtained extracts was characterized in terms of their ability to inhibit xahntine oxidase enzyme, which is a validated target for the therapeutic treatment of hyperuricemia.

Mild Organosolv Delignification of Residual Aspen Bark after Extractives Isolation as a Step in Biorefinery Processing Schemes

European aspen (Populus tremula (L.) (Salicaceae)) bark is a promising raw material in multi-step biorefinery schemes due to its wide availability and higher content of secondary metabolites in comparison to stem wood biomass. The main objective of this study was to investigate the major cell wall component-enriched fractions that were obtained from aspen bark residue after extractives isolation, primarily focusing on integration of separated lignin fractions and cellulose-enriched bark residue into complex valorization pathways. The “lignin first” biorefinery approach was applied using mild organosolv delignification. The varying solvent systems and process conditions for optimal delignification of residual aspen bark biomass were studied using a response surface methodology approach. The conditions for maximum process desirability at which the highest amount of lignin-enriched fraction was separated were as follows: 20-h treatment time at 117 °C, butanol/water 4:1 (v/v) solvent system with solid to liquid ratio of 1 to 10. At optimal separation conditions, lignin-enriched fraction exhibited a higher content of β–O–4 linkages vs. C–C linkages content in its structure as well as a high amount of hydroxyl groups, being attractive for its further valorization. At the same time, the content of glucose in products of cellulose-enriched residue hydrolysis was 52.1%, increased from 10.3% in untreated aspen bark. This indicates that this fraction is a promising raw material for obtaining cellulose and fermentable glucose. These results show that mild organosolv delignification of extracted tree bark can be proposed as a novel biorefinery approach for isolation of renewable value-added products with various application potentials.