Sequential Solvent Extraction Research Articles

In Vivo Antidiarrheal Potential of the Leaf Extract of Maytenus addat (Loes.) Sebsebe and Its Major Compound.

Diarrhea continues to be one of the top causes of death in children under the age of five, particularly in developing nations. In Ethiopian traditional medicine, a variety of medicinal plants are used to treat diarrhea. One of these plants is Maytenus addat (Loes.) Sebsebe (fam. Celastraceae), which is endemic to the Afromontane forests, especially along forest margins, of Ethiopia. The air-dried powdered leaves of M. addat were macerated with 80% methanol to yield a crude extract. Additionally, the powdered plant material underwent sequential solvent extraction using chloroform, methanol, and water to obtain solvent fractions. The 80% methanol leaf extract, solvent fractions, and an isolated compound from M. addat were evaluated for their antidiarrheal activity using castor oil-induced diarrheal model, anti-enteropooling test, and charcoal meal test in mice. The results showed that the 80% methanolic leaf extract significantly reduced the onset of diarrhea, the weight of feces, and the frequency of defecation in all the tested doses. The methanol and water fractions of the hydroalcoholic extract also exhibited dose-dependent antidiarrheal activity, with the methanol fraction showing the highest activity at 400 mg/kg dose. Subsequently, the most active methanol fraction was subjected to C-18 solid phase extraction, resulting in the isolation of a 3-hydroxyflavone, identified as quercetin by ESI-qToF-MS, 1H, and 13C-NMR spectroscopic techniques. Quercetin demonstrated a strong antidiarrheal activity in a dose-dependent manner. Thus, the present study provided evidence that the leaves of M. addat possess genuine antidiarrheal activity upholding the traditional medicinal use of the plant for the treatment of diarrhea. The findings also suggest that quercetin is responsible, in full or in part, for the activity of the plant.

The effect of lactic acid fermentation on the phytochemical content of fig leaf extracts compared to single solvent and sequential solvents extraction

The aim of this study was to compare the antioxidant, natural products, and polyphenolic profiles of Ficus carica L. leaf extracts obtained with a sequential solvent extraction (n-hexane, dichloromethane, ethyl acetate, and methanol), a single solvent extraction with one of three different solvents (methanol, ethanol and ethyl acetate), and a fermentation assisted extraction. Extracts were assessed by high-performance thin-layer chromatography (HPTLC) fingerprinting pattern (before and after derivatization with DPPH free radical, anisaldehyde-sulfuric acid reagent and ferric chloride) and with ATR-FTIR phytochemical profiling. The results show that sequential solvents extraction may maximise the extraction of natural products, especially polyphenolics. However, the highest antioxidant activity was achieved with a single solvent extraction with ethyl acetate. Furthermore, fermentation assisted extraction further improves extraction of antioxidants when compared to single extraction from nonfermented material. In conclusion, brining and spontaneous lactic acid fermentation of plant material is a highly desirable method for improving the functional properties of extracts due to its low cost and low energy requirements.

Non-targeted discovery of high-value bio-products in Nicotiana glauca L: a potential renewable plant feedstock

The evaluation of plant-based feedstocks is an important aspect of biorefining. Nicotiana glauca is a solanaceous, non-food crop that produces large amounts of biomass and is well adapted to grow in suboptimal conditions. In the present article, compatible sequential solvent extractions were applied to N. glauca leaves to enable the generation of enriched extracts containing higher metabolite content comparing to direct leaf extracts. Typically, between 60 to 100 metabolite components were identified within the fractions. The occurrence of plant fatty acids, fatty acid alcohols, alkanes, sterols and terpenoids was detected by gas liquid chromatography–mass spectrometry (GC–MS) and metabolite identification was confirmed by comparison of physico-chemical properties displayed by available authentic standards. Collectively, co-products such waxes, oils, fermentable sugars, and terpenoids were all identified and quantified. The enriched fractions of N. glauca revealed a high level of readily extractable hydrocarbons, oils and high value co-products. In addition, the saccharification yield and cell wall composition analyses in the stems revealed the potential of the residue material as a promising lignocellulosic substrate for the production of fermentable sugars. In conclusion a multifractional cascade for valuable compounds/commodities has been development, that uses N. glauca biomass. These data have enabled the evaluation of N. glauca material as a potential feedstock for biorefining.Graphical

Analysis of iron-rich hydrochloric acid solutions for uranium, thorium, rare-earth elements and other heavy metals

A simple solvent extraction method is described for the separation of trace elements including uranium (U), thorium (Th) and rare-earth elements (REEs) from industrially processed iron-rich hydrochloric acid solutions. Iron (Fe) causes severe spectral interference during the analysis of trace elements using inductively coupled plasma optical emission spectrometer (ICP-OES) and U by light-emitting diode (LED)-based fluorimeter (LEDF). The spectral interferences of Fe on trace elements are studied and documented. Sequential solvent extractions using methyl isobutyl ketone (MIBK) effectively removed the highly interfering Fe from these processed acid solutions, thereby enabling accurate and sensitive determination of Cd, Zn, Pb, Co, Ni, Cr, V, Cu, Sr, Zr, Ti, REEs including radioactive elements like U and Th. Solvent extraction parameters like the number of extractions, aqueous-organic ratio and acidity have been optimized for removal of Fe. The accuracy of the method has been established by analyzing synthetically prepared hydrochloric acid solutions by spiking-recovery method. Ion exchange separation of REEs using Dowex 50 × 8 cation exchange resin has been also studied and reported. The precision obtained has been well within ± 10% RSD for elements having concentration above 10 mg L−1 and ± 15% for elements having concentration below 10 mg L−1 for replicate (n = 5) measurements.

Sensory-directed isolation and identification of an intense salicin-like bitter compound in infected teas with bird’s eye spot disease

Teas infected with bird’s eye spot disease generally exhibited a lingering and long-lasting, salicin-like bitter taste, which was unpalatable to consumers. Sensory-directed isolation processes have been performed in this study to investigate the salicin-like bitter compounds in infected teas. Results showed that infected teas were extracted using a 70% methanol aqueous solution to produce methanol extract, which was then further separated by sequential solvent extraction (SSE) to obtain dichloromethane extract, which contained the salicin-like bitter compounds. The dichloromethane extract was then isolated by flash chromatography to produce two salicin-like bitter fractions, eluted using 60% and 65% methanol aqueous solution. Finally, these two salicin-like bitter fractions were analyzed by RP-HPLC using 60–68% and 70–75% methanol aqueous solution, respectively, affording the location of the salicin-like bitter compounds in RP-HPLC chromatograms. Moreover, a new ursane-type triterpenoid, camellisin A methyl ester, was identified from infected teas. This study has provided preliminary isolation methods of salicin-like bitter compounds from the infected teas, which were essential to designing targeted debittering strategies for infected teas and improving the quality of the finished tea and the effective utilization of fresh tea leaves.

Anti-Multidrug resistant activity of endophytic fungi isolated from the stem of Tradescantia pallida against Gram-positive pathogens

The present study aimed at the isolation and in vitro anti-MRSA and antioxidant properties of endophytic fungi derived from the stem of Tradescantia pallida. The fungal endophytes were isolated in a PDA agar medium. A total of seven isolates were recovered. Sequential solvent extraction was done using different polarity solvents and the crude extracts obtained were tested for their antagonistic activity against drug-resistant bacteria. In vitro, the antioxidant activity of the potent fungus was carried out by DPPH assay. Crude extract from TPS2 isolate displayed maximum inhibition towards Methicillin-resistant Staphylococcus aureus ATCC 43300 and 700699. It also exhibited free radical scavenging activity in the range of 30 to - 85%. The potential isolate was identified as Aspergillus niger. Thus, we conclude that the dichloromethane crude extract of A.niger fungal can produce antibacterial and antioxidant compounds. Hence the bioactive metabolites can be probed as antibacterial agents in treating infectious diseases.

Combination of HPLC–orbitrap‐MS/MS and network pharmacology to identify the anti‐inflammatory phytochemicals in the coffee leaf extracts

AbstractIn this study, we investigated the phytochemical compositions and the associated anti‐inflammatory activity of coffee leaf fractions prepared by sequential solvent extraction using high‐performance liquid chromatography–orbitrap‐tandem mass spectrometry (HPLC–orbitrap‐MS/MS) combined with network pharmacology. The results showed that the ethyl acetate fraction (EAC‐L) had the highest nitric oxide (NO), ABTS, and DPPH free radical scavenging abilities due to the higher concentrations of mangiferin, rutin, 3,5‐dicaffeoylquinic acid (3,5‐diCQA), and 4,5‐diCQA. The extraction solvents had the greatest impact on the anti‐inflammatory activity of coffee leaf fractions, whereas the processing method had the most significant effect on the antioxidant activity of these fractions. Untargeted metabolomics analysis using HPLC–orbitrap‐MS/MS indicated that palmitic acid, 3,4‐dihydroxybenzaldehyde, and caffeic acid may be involved in the anti‐inflammatory activity of EAC‐L fraction obtained from fresh coffee leaves. On the other hand, processed coffee leaf fraction exhibited anti‐inflammatory activity that was attributed to the presence of 9S,13R‐12‐oxophytodienoic acid, pinocembrin, and quercetin, which have high degree values associated with the inflammation network. Gene ontology and Kyoto encyclopedia of genes and genomes enrichment of network pharmacology analysis showed that these 35 differential compounds in the coffee leaf fractions affect cell transcription, apoptosis, phosphorylation, NO synthesis, phosphatidylinositide 3‐kinases‐protein kinase B (PI3K‐Akt) signaling pathway, focal adhesion, hypoxia‐inducible factor‐1, hepatitis, cancer, and so on. This result indicated that coffee leaf extract may also function as an inhibitor for inflammation‐related cancers. The findings of our research are valuable in guiding the extraction of anti‐inflammatory components from coffee leaves.

Extraction of Organic Compounds From Lacustrine Oil-Prone Shales and the Effect on Nanopore

Lacustrine oil-prone shale at the oil-generation stage develops a large number of nanopores; however, the influence of fluid–shale interactions on the nanopores of lacustrine shale is poorly understood. A suite of mature lacustrine shales from the Songliao Basin Qingshankou Formation was performed on sequential organic solvent (petroleum ether and mixture of dichloromethane and methanol) extractions, and nitrogen and carbon dioxide adsorptions, Rock-Eval pyrolysis and field emission scanning electron microscopes (FE-SEM) observation. The sequential extractions show a decrease in total organic matter (TOC) and in the exacted organic matter content of shale, but an increase in the specific area (SBET) and pore volume of the extracted residues. Before and after extractions, the relationships between the extracted amount of OM and SBET, pore volume and their cumulative increments reveal OM as a main factor affecting the development of nanopores in these shales. The reasons are 1) SBET and mesopores are mainly blocked by EOMs in the initial samples, 2) the cumulative increases of SBET and mesopores are dominantly controlled by the extracted amount of hydrocarbons during petroleum ether extraction, and 3) both hydrocarbons and NSOs (resins and asphaltenes) have an influence on the cumulative increases of SBET and mesopores, and kerogen exposed more open porous-organic mesopores after the EOMs in the extracted shales. Here, further work concludes that oils adsorbed on pore surfaces are dominantly distributed on nanopores less than 10 nm, and free oils occur when the threshold of the average pore width in studied shales is over 11.7 nm.

Separation of high added-value chemical compositions derived from biomass pyrolysis liquid via sequential multi-step pH adjustment

The complexity of the components in pyrolysis liquid causes serious problems for its downstream utilization. In order to increase the added value and commercialization of pyrolysis liquid, a novel method was developed by combining the sequential multi-step pH adjustment and organic solvent extraction methods to separate the chemical components of crude pyrolysis liquid. The chemical composition of crude pyrolysis liquid was determined by fourier transform infrared spectrometry and gas chromatography–mass spectrometry. The results showed that acids (17.54%) and phenolics (57.44%) were the major constituents. The neutral compounds (e.g. ketones) (38.57%) were enriched at pH 14. Methoxyphenols (e.g., 2,6-dimethoxyphenol) were separated at pH 11, accounting for 63.4%. Phenol and maltol were mainly found at pH 9 and 7, with relative contents of 11.30% and 10.09%, respectively. At pH 6 and 4, acetic acid was the most abundant compound, with contents of 17.23% and 20.72%, respectively. The main compound at pH 2 was 2-methyl-propanoic acid anhydride (35.05%). Principal component analysis (PCA) results showed that the PC1 and PC2 components explained 38.8% and 26.2% of the chemical variance, respectively. The DPPH free radical scavenging rate showed positive correlation with the phenolic component, and was negatively correlated with the acid component. The highest DPPH free radical scavenging rate (88%) was obtained at pH 11. This study provided a theoretical reference for the separation of target components in pyrolysis liquid.

Fine-tune of lignin properties by its fractionation with a sequential organic solvent extraction

In this work, different lignins were obtained from two different extraction methods (kraft and organosolv) but from the same raw material (Eucalyptus globulus sp.). They were subsequently fractionated to determine the differences of each extraction method and their corresponding physicochemical properties found in fractionation sequence and obtained fractions. The goal of the fractionation was to obtain lignin fractions with narrower molecular weight distribution and lower polydispersity index (PI). The solvent sequence was designed based on the environmental friendly properties, health and safety assessments of the selected organic solvents: (methanol (MeOH), ethanol (EtOH), propan-2-one (DMK), ethyl acetate (EtOAc), propan-1-ol (nPrOH), propan-2-ol (iPrOH), butan-2-one (MEK), and butan-1-ol (tBuOH)). The different fractions obtained were characterised to determine their chemical structure by several analytical techniques, such as Fourier Transformed Infrared Spectroscopy (FTIR), Ultraviolet (UV), Phosphorus-31 Nuclear Magnetic Resonance (31P NMR), Pyrolysis–Gas Chromatography/Mass Spectrometry (Py-GC/MS), Thermogravimetric analysis (TGA), and Differential scanning calorimetry (DSC). In addition, Gel Permeation Chromatography (GPC) was used to obtain the molecular weight distribution. This study showed an effective method for obtaining homogeneous lignins with specific structures and properties depending on the solvent and molecular weight attained. Moreover, the method designed was found to be effective regardless of the lignin extraction process employed; besides, various lignin fractions were obtained which were different from each other, having specific target applications depending on their structure and chemical properties, ranging from small molecules with abundant reactive sites to act as active materials or copolymer reagents for many applications, to larger and more inactive molecules with higher thermal resistivity.

Crepidium sect. Crepidium (Orchidaceae, Malaxidinae)-Chemical and Morphological Study of Flower Structures in the Context of Pollination Processes.

Crepidium is a large genus of mainly pantropical orchids. The lips of its flowers are upwardly directed and do not serve as landing platforms for pollinators. This role is assumed by the dorsal sepal and/or gynostemium. Information about the pollination and floral morphology of this genus is scarce. To date, no papers have been published on these topics. Field observations have revealed that the flowers are visited by small flies, midges, fruit flies, other small dipterans, ants, spiders, and mites. Preliminary observations revealed at least two forms of small liquid droplets secreted on the lip surface of Crepidium species: simple secretions from epidermal cells, and cell sap released upon the rupturing of raphide-producing cells. Further research revealed that this was the first time liquid secretion was recorded in this genus. Floral secretions were subjected to sequential organic solvent extraction and gas chromatography–mass spectrometry (GC–MS). Floral parts were investigated by means of scanning (SEM) and transmission electron microscopy (TEM), and histochemical tests. The presence of liquid droplets on the lip of Crepidium, the presence of a food reward, and the sequence of raphide development are reported here for the first time.

Isolation, Characterization and Quantitation of Photoactive phases of Titanium (IV) oxide in skin-lightening products

Titanium (IV) oxide (TiO2) is used as a physical blocker of ultraviolet (UV) radiation in many skin-care products. Absorption of TiO2 through the skin is likely to interact with viable tissues because UV radiation absorption generates toxic reactive oxygen species such as hydroxyl radicals. Studies on the acute toxicity of TiO2 nanoparticles in mammals indicate that intra-tracheal instillation, intraperitoneal injection or oral instillation of TiO2 particles to the animals evoke an inflammatory response as well as certain histopathological changes. Ultrafine particles of the anatase form of titanium (IV) oxide, which are smaller than 0.1 microns, are pathogenic. In this work eight skin-lighteners containing TiO2 from South African market were studied. The TiO2 was extracted by a fusion technique and quantified by inductively coupled plasma-optical emission spectrometry (ICP-OES). Sequential solvent extraction was employed to isolate TiO2 particles for characterization employing high-resolution transmission electron microscopy (HR-TEM) and powder X-ray diffraction (PXRD). All samples considered in this study meet agreeable TiO2 % (m/m) levels as specified by all health regulatory bodies. Both forms of TiO2: anatase and rutile, were found to be present. Most samples contained nano-TiO2 in the particle size range of 16.23 nm to 51.47 nm that could lead to detrimental effects. The fact that the anatase form, known for its photocatalytic activity, was present, is a cause for concern.

In vitro biomineralization and osteogenesis of Cissus quadrangularis stem extracts: An osteogenic regulator for bone tissue engineering

Contemporary demand calls for a high restorative index as an indispensable requirement for bone tissue engineering scaffolds, where therapeutic agents of natural origin function as a modulator for new bone formation become of utmost importance. The study presents a systematic investigation of the edible stem part of Cissus quadrangularis (CQ) as a natural resource of bioactive metabolites capable of invoking early biomineralization and osteogenesis in vitro. Phytochemical screening of CQ stem extracts (sequential solvent extraction: polarity hexane<chloroform<ethyl acetate<methanol<water) was performed by qualitative and quantitative assays, which are substantiated by UV-Visible and FTIR spectroscopic analyses. Cytocompatibility and proliferation index of the extracts and their effect on cellular architecture were investigated by MTT assay (different time points) and F-actin/DAPI staining, respectively, in Human Osteosarcoma (HOS) cells. MTT results exemplified profound cell proliferation index for hexane (HE) and aqueous (WE) extracts (24 and 48 h), while Alizarin Red S and von-Kossa staining validated early biomineralization (day 7). The activity of the early bone marker, Alkaline phosphatase (ALP), on day 7 authenticates the effective osteogenic potential of HE and WE compared to other extracts, configuring abundance of bone regenerative phytochemicals in HE and WE and present ample opportunities for customized bone tissue engineering.

Mode-Dependent Antiviral Activity of Medicinal Plant Extracts against the Mosquito-Borne Chikungunya Virus.

The lack of specific treatment for chikungunya fever makes the need for anti-chikungunya virus agents more crucial. This study was conducted to evaluate 132 extracts obtained by sequential solvent extraction from 21 medicinal plants for cytopathic effect inhibitory activity using virus-infected Vero cells in two different sample introduction modes. Among the extracts, 42 extracts (31.8%) from 12 plants in the concurrent mode and three extracts (2.3%) from a plant in the non-concurrent mode displayed strong cytopathic effect inhibitory activity (cell viability ≥70%). Viral load quantification analysis unveiled that the extracts of Clinacanthus nutans (chloroform, ethyl acetate, and ethanol), Hydrocotyle sibthorpioides (ethanol), and Ocimum americanum (ethanol and methanol) hindered the release of viral progeny from the infected cells while the extracts of Ficus deltoidea (ethanol), Gynura bicolor (water), H. sibthorpioides (water), and O. americanum (chloroform and ethyl acetate) blocked the entry of virus into the cells. The extracts of Diodella sarmentosa (ethyl acetate), Diplazium esculentum (chloroform, ethyl acetate, and ethanol), and G. bicolor (ethanol) possessed virucidal effect and caused 5.41-log to 6.63-log reductions of viral load compared to the virus control. The results indicate that these medicinal plants are potential sources of anti-chikungunya virus agents that have varied modes of action.

Allelopathic and Herbicidal Effects of Crude Extract from Chromolaena odorata (L.) R.M.King and H.Rob. on Echinochloa crus-galli and Amaranthus viridis.

The present study was aimed at investigating the allelopathic effects of a crude extract from Chromolaena odorata (L.) R.M.King and H.Rob. (Siam weed). The effects of 70% crude ethanol extract from the whole plant, leaf, stem, and root on the germination and growth of Echinochloa crus-galli and Amaranthus viridis seedlings were evaluated using Petri-dish tests under laboratory conditions. Crude extracts from the leaf showed the highest inhibitory activity. The leaf extract (OR) was further separated by sequential solvent extraction to provide hexane (HX), ethyl acetate (ET), and butanol (BU) fractions, which were also evaluated using Petri-dish tests. The hexane fraction was significantly the most active; therefore, it was selected for formulation in a concentrated suspension and tested for its herbicidal characteristics. The formulation showed greater early post-emergence than post- and pre-emergence activities, respectively. The physiological mechanism of the formulation was tested against E. crus-galli and showed that chlorophyll a and b and the carotenoid contents of the leaf dramatically decreased when the concentration was increased, suggesting its ability to disrupt the process of photosynthesis. As thiobarbituric acid reactive substances also occurred in the leaf of E. crus-galli, this suggests lipid peroxidation and cell disruption. These results represent the possibility that C. odorata extract contains inhibitory compounds with herbicidal activity and could be used as an early post-emergence herbicide for weed control.

Antimicrobial, Antioxidant and Antiproliferative Properties of the Leaves of Senna siamea

The aim of this study was to investigate the antimicrobial, antioxidant and antiproliferative activities of leaves of Senna siamea. A sequential solvent extraction procedure was used in extracting powdered Senna leaves, starting with hexane, ethylacetate, ethanol and distilled water, respectively. Dry extracts obtained were tested at various concentrations against Pseudomonas aeruginosa, staphylococcus aureus, Salmonella typhi and Candida albicans. Antioxidant (Qualitative and quantitative) and antiproliferative tests were carried out on samples of the dry extracts. Ethylacetate extract of Senna siamea showed the highest antibacterial activity against S. typhi (zone of inhibition 15.0 mm) at concentration of 500mg/ml. The aqueous extract had the highest antioxidant activity, evidenced by a low IC50 value of 12.89µg/ml. Antiproliferative activity was determined by calculating the percentage inhibition of germination of Sorghum bicolor L. seeds under appropriate conditions. Plants that inhibit seed germination may inhibit tumour growth. At 24 hours, the plant showed strong antiproliferative activity as evidenced by the high percentage inhibition. Ethanolic extract had the highest antiproliferative activity (90%) at 5000µg/ml, followed by the aqueous extract (88.5%). However, at 48 hours, all organic extracts showed very weak antiproliferative activity as evidenced by the low % inhibition. Only the aqueous extract showed considerable antiproliferative activity at 5000µg/ml (45%). This implies that the aqueous extract has considerable antiproliferative activity, hence, it may be a promising anticancer drug or has components that have anticancer properties. This shows that Senna leaves could serve as source of bioactive compounds with potential antimicrobial, antioxidant and anticancer properties.

Formation of pure nanoparticles with solvent-fractionated lignin polymers and evaluation of their biocompatibility

This study aimed to determine the effects of lignin characteristics (mainly molecular weight, functional groups, and internal linkages) on nanoparticle formation. First, five different lignin fractions (Mw 1460–12,900) were obtained from commercial kraft lignin (KL) by sequential solvent extraction. Functional groups and internal linkages were determined in lignin fractions, each fraction consisting of different levels and ratios. Second, spherical lignin nanoparticles (i.d. 193–1039 nm) were synthesized by nanoprecipitation at different pre-dialysis concentrations (1, 2, 4, and 6 mg mL−1 THF) with the different fractions (F1, F2, F3, F4, and F5). The study revealed that larger particles consisted of lignin fractions of lower molecular weight and higher phenolic group content (KL-F1 and F2), while smaller but non-uniform particles were produced from fractions of higher molecular weight and lower phenolic group content (KLF4 and F5). Every zeta potential value of the particle exceeded −35 mV. The nanoparticles from raw kraft lignin exhibited no significant cytotoxicity, hemotoxicity, and hypersensitivity. This study revealed that molecular weight and hydroxyl group content in the lignin highly correlated with nanoparticle properties. The present kraft lignin nanoparticles have potential for use in various polymer-based nanotechnology.

Identification of bitter‐taste compounds in class‐III caramel colours

AbstractCaramel colours become one of the most widely used colorings in various foods and beverages due to their total miscibility with water and great coloring properties by containing colloidal aggregates. Bitterness in caramel colours can negatively influence their acceptability. The sequential solvent extraction (SSE) and semi‐preparative liquid chromatography (SP‐LC) combined with the taste dilution analysis were applied to identify the most intense bitter‐tasting compounds in class‐III caramel colours. Four main compounds with the highest bitterness intensity were isolated and structurally elucidated based on high resolution‐electrospray ionization‐mass spectrum (HR‐ESI‐MS), nuclear magnetic resonance (NMR) spectroscopy and gas chromatography‐mass spectrum (GC‐MS): 2,3‐dihydro‐3,5‐dihydroxy‐6‐methyl‐4(H)‐pyran‐4‐one (DDMP), 5‐(hydroxymethyl) furfural (HMF), furfural and 5‐methylfurfural (MF). The threshold concentrations of DDMP, HMF, furfural and MF were 14.3, 30.0, 4.4 and 17.5μmol L−1, respectively. Furthermore, two volatile bitter compounds were identified: [5‐(di‐methoxymethyl) furan‐2‐yl] methanol (DMFM) and 2,3,4,4‐tetramethyl‐pentane‐1,3‐diol (TMP). Based on the composition of the caramel colours and the structures of these compounds, Maillard reaction was supported to generate these bitter compounds in caramel colour‐III.

An integrated approach for hemicellulose extraction from forest residue

An alkali-mediated hydrothermal approach was optimized for partial extraction of high-purity hemicellulose (xylan) from a timber waste product (unbleached eucalyptus sawdust). The extraction process was: a) extractives removal using sequential solvent extraction; b) alkali-mediated hydrothermal extraction of hemicellulose; and c) purification of the isolated hemicellulose fraction. Biomass was extracted in an autoclave at a fixed temperature of 121 °C while varying the extraction time (1 h to 2.5 h) and alkali concentration (10%, 15%, and 20% w/v). Using this simple approach, high purity polymeric hemicellulose with molecular mass (21 to 30 kDa) was recovered in yields of 35 to 37%. The isolated hemicellulose can be chemically transformed into high-value commercial products such as prebiotics (xylooligosaccharides), surfactants, hydrogels, and food packaging materials. The purified residue can be utilized in existing kraft pulping processes. The integration of hemicellulose extraction into existing pulping process represents additional valorization of timber resources.

Insights into the Inhibition Mechanism of Human Pancreatic α-Amylase, a Type 2 Diabetes Target, by Dehydrodieugenol B Isolated from Ocimum tenuiflorum.

Use of human pancreatic α-amylase (HPA) inhibitors is one of the effective antidiabetic strategies to lower postprandial hyperglycemia via reduction in the dietary starch hydrolysis rate. Many natural products from plants are being studied for their HPA inhibitory activity. The present study describes isolation of dehydrodieugenol B (DDEB) from Ocimum tenuiflorum leaves using sequential solvent extraction, structure determination by one-dimensional (1D) and two-dimensional (2D) NMR analyses, and characterization as an HPA inhibitor using kinetics, binding thermodynamics, and molecular docking. DDEB uncompetitively inhibited HPA with an IC50 value of 29.6 μM for starch and apparent Ki′ of 2.49 and Ki of 47.6 μM for starch and maltopentaose as substrates, respectively. The circular dichroism (CD) study indicated structural changes in HPA on inhibitor binding. Isothermal titration calorimetry (ITC) revealed thermodynamically favorable binding (ΔG of −7.79 kcal mol–1) with a dissociation constant (Kd) of 1.97 μM and calculated association constant (Ka) of 0.507 μM. Molecular docking showed stable HPA–inhibitor binding involving H-bonds and Pi-alkyl, alkyl–alkyl, and van der Waals (vDW) interactions. The computational docking results support the noncompetitive nature of DDEB binding. The present study could be helpful for exploration of the molecule as a potential antidiabetic drug candidate to control postprandial hyperglycemia.