Globulus Bark Research Articles

Supercritical fluid extraction of phenolic compounds from Eucalyptus globulus Labill bark

The supercritical fluid extraction (SFE) of phenolic compounds from Eucalyptus globulus bark was carried out along with detailed analysis of the extracts for the first time. The extracts were accessed in terms of: (i) extraction yield (EY), (ii) total phenolic content by Folin–Ciocalteu method (TPC), (iii) phenolics quantified by high performance liquid chromatography (PC-HPLC), and (iv) antioxidant activity (AA). Preliminary runs were performed with pure and modified CO2, using ethanol (EtOH), ethyl acetate, and water. The CO2/EtOH mixture provided the best extraction yield, high total phenolic content and antioxidant activity. Results also demonstrated high selectivity of the CO2/EtOH mixture to the extraction of flavanones, particularly eriodictyol and naringenin; and to the O-methylated flavonol isorhamentin, also found in abundance. To analyse the influence of temperature, ethanol content and flow rate on SFE at 300bar using CO2/EtOH, a full 23 design of experiments was accomplished. The most favourable conditions under the experimental range studied were found as 70°C, 20% ethanol, and 10g of CO2min−1, for which EY=0.48%, TPC=57.22mgofgallicacidequivalents(GAE)g−1 of extract, PC-HPLC=119.46mgg−1 of extract, and AA=49.74mgofascorbicacidequivalents(AAE)g−1 of extract.

Supercritical fluid extraction of triterpenic acids from Eucalyptus globulus bark

Eucalyptus globulus bark contains four significant families of compounds, namely triterpenic (TT) acids (betulinic, betulonic, oleanolic and ursolic acids, and the acetylated forms of the latter two), long chain aliphatic alcohols, fatty acids, and sterols. The first group is the most abundant and possesses demonstrated bioactivity, which raises the importance of this biomass. The supercritical fluid extraction (SFE) of E. globulus bark was carried out in this work with carbon dioxide at 100, 140 and 200bar, and 40, 50 and 60°C, and the extracts were analyzed by GC–MS. The results are compared with those obtained by Soxhlet with dichloromethane, and the influence of the operating conditions upon the global yield and the individual yields of the triterpenic acids is discussed in detail. The acetylated TT acids imparted a large effect on the extraction yields, as they appeared in large concentrations on the extracts independently of their absolute loadings in the bark. The polarity of the free acids, higher than that of their acetyl derivatives, justifies this behavior. Modeling calculations were also performed for interpreting the SFE results. The experimental observations are in agreement with predictions accomplished for the solubilities and mass transfer fluxes of ursolic acid and 3-acetylursolic acid that were chosen as key TT acids in the process.

Antioxidant effects and phytochemical analysis of crude and chromatographic fractions obtained from Eucalyptus globulus bark

Eucalyptus globulus is extremely used in traditional medicine in Algeria and its leaf extract is included as one of the antioxidant in the list of existing food additives in Japan. In the present study, the crude extract from bark of this plant and its fractions obtained by Sephadex LH-20 column were studied to quantify their levels of phenolic compounds and their antioxidant activity (ferric reducing power, 1,1-diphenyl-2-picryl hydroxyl (DPPH•) radical scavenging activity and scavenging of hydrogen peroxide). All extracts exhibited a reducing power effect higher than that of a-tocopherol. It was observed that crude extract displayed the highest DPPH• scavenging ability (IC50115.40 ig/ml) followed by a- tocopherol (IC50 233.78 ig/ml). Crude extract also displayed the highest ability to neutralize hydrogen peroxide at 65 ig/ml (75.55%), followed by a-tocopherol (20.07%) at the same concentration. The results show that fractions b and c exhibited lower antioxidant activities for the three antioxidant tests comparatively to that of crude extract. Fraction a exhibited the lowest antioxidant capacity. Key words : Eucalyptus globulus , bark extract, phenolic compounds, antioxidant effect, Sephadex LH-20 column.

Extraction of Polyphenolic Compounds from Eucalyptus globulus Bark: Process Optimization and Screening for Biological Activity

The bark of Eucalyptus globulus is a promising source of polyphenolic compounds that could be extracted employing polar solvents. Extraction experiments were planned according to the Box–Behnken design to evaluate the effect of temperature and time of extraction and the ethanol/water ratio on the dependent variables total phenolic content (TPC; as gallic acid equivalents, GAE), antioxidant activity (AA; as millimoles of ascorbic acid equivalents, AAE), proanthocyanidins (Pac; as mimosa extract equivalents, MEE), Stiasny number (SN), and coextracted total carbohydrates (TC). Response surface models were developed, and statistical analysis of variance was performed. A maximum of TPC of 32% (wGAE/wextract) was achieved for 264 min, 82.5 °C, and 52% ethanol corresponding to about 2% of the bark weight. These conditions are close to those leading to maximum values of compounds with AA (2.1 mmolAAE/gextract) and Pac 14% (wMEE/wextract). TC in the extract and the SN predicted were 22.7% (wTC/wextract) and 37, re...

Properties of fly ash from forest biomass combustion

Nowadays forest biomass is increasingly being used as a renewable energy source. This application, however, has the disadvantage that it produces large quantities of fly ash. The characteristics of the fly ashes produced differ depending on the source of the biomass and the combustion conditions; and these characteristics determine its eventual application (in cement, nutrient soil, etc.). In addition the absence of heavy metals in the fly ashes makes them very useful as a means of obtaining activated carbon, zeolite or belite cement. In this work fly ashes from the combustion of forest biomass (Eucalyptus globulus bark) in a pulp mill in Northern Spain were investigated. The ashes were produced by two types of combustion systems: grate furnace and fluidized bed combustion. Close examination of the raw fly ashes and their corresponding sieved fractions of different grain size led to the following conclusions: (i) fluidized bed combustion of forest biomass is more efficient than grate furnace combustion; (ii) unburned carbons tend to be concentrated in the granulometric fractions of higher grain size, particularly in the fly ash from grate furnace combustion; (iii) the higher grain size fraction shows good textural properties that make it a potential precursor for activated carbons, (iv) the largest concentrations of mineral matter occur in the finest granulometric fractions which could be used as fertilizers or as raw material to obtain zeolites or belite cement, and (v) the intermediate granulometric fraction from fluidized bed combustion, due to its high concentration of SiO2 originating from the combustor bed, could be used again to make up the combustor bed.

Characterization of Phenolic Components in Polar Extracts of Eucalyptus globulus Labill. Bark by High-Performance Liquid Chromatography–Mass Spectrometry

High-performance liquid chromatography-electrospray ionization mass spectrometry (HPLC-ESI-MS) and tandem mass spectrometry (MS(n)) were used to investigate the phenolic constituents in methanol, water, and methanol/water extracts of Eucalyptus globulus Labill. bark. Twenty-nine phenolic compounds were identified, 16 of them referenced for the first time as constituents of E. globulus bark, namely, quinic, dihydroxyphenylacetic, and caffeic acids, bis(hexahydroxydiphenoyl (HHDP))-glucose, galloyl-bis(HHDP)-glucose, galloyl-HHDP-glucose, isorhamentin-hexoside, quercetin-hexoside, methylellagic acid (EA)-pentose conjugate, myricetin-rhamnoside, isorhamnetin-rhamnoside, mearnsetin, phloridzin, mearnsetin-hexoside, luteolin, and a proanthocyanidin B-type dimer. Digalloylglucose was identified as the major compound in the methanol and methanol/water extracts, followed by isorhamnetin-rhamnoside in the methanol extract and by catechin in the methanol/water extract, whereas in the water extract catechin and galloyl- HHDP-glucose were identified as the predominant components. The methanol/water extract was shown be the most efficient to isolate phenolic compounds identified in E. globulus bark.

The breakdown of Blue Gum (Eucalyptus globulus Labill.) bark in a Portuguese stream

Eucalypt forests produce large amounts of bark, which potentially accumulate in streams, constituting an important carbon and nutrient source for benthic food webs. In this study, we compared the breakdown (and associated microbial activity and diversity and invertebrate abundance) of Eucalyptus globulus bark and leaves, enclosed in coarse and fine mesh bags, in a 3 rd order stream of central Portugal. Biofilm development on bark was also analyzed with scanning electronic microscopy and respiration rates quantified. After 90 days of incubation, bark lost 21-51 % of its initial mass while leaves lost 48-57 %. Fungal biomass (as determined from ergosterol concentrations) increased over time and was higher in leaves than in bark (79 vs. 50 mg [g AFDM] -1 at day 90). Sporulation by aquatic hyphomycetes was only observed after 2 weeks (leaves and bark in coarse mesh bags) or 2 months (bark in fine mesh bags). The initial litter mass converted into conidia in leaves was 7-45 fold the values found in bark. Fungal communities were dissimilar in the two substrates with bark presenting the lowest number of species. Lunulospora curvula and Anguillospora crassa dominated the fungal communities in bark, while L. curvula and Tetrachaetum elegans were the dominant species in leaves. Respiration rates, as a measurement of microbial activity, were lower in bark than in leaves (0.10 vs. 0.25 mg O 2 [g AFDM] -1 h -1 in fine mesh and 0.11 vs. 0.39 mg O 2 [g -1 AFDM] -1 h -1 in coarse mesh). Biofilms in bark clearly increased after 15 days of immersion and contributed to 6-85 % of total oxygen consumption. Overall, the results suggest that microbial decomposition pathways dominate the processing of eucalyptus leaves and bark, although leaching and physical fragmentation may stimulate and facilitate the breakdown of bark.

New glucosides from Eucalyptus globulus wood, bark and kraft pulps

New glucosides from Eucalyptus globulus wood, bark and kraft pulps

WITHIN–TREE VARIATION IN PHLOEM CELL DIMENSIONS AND PROPORTIONS IN EUCALYPTUS GLOBULUS

The axial variation of bark thickness and quantitative anatomical features of Eucalyptus globulus bark were analysed for one site based on individual measurements of ten 15-year-old trees at six height levels (DBH, 5%, 15%, 35%, 55% and 75% of total tree height). The parameters studied were: length, tangential diameter and percentage of sieve tubes; length, width, cell wall thickness and percentage of fibres; height and percentage of rays; percentage of sclereids in the secondary phloem. Bark thickness decreases from base to top of the tree. Fibre width and wall thickness decrease from base upwards. No distinct axial patterns of variation were observed for the other biometric variables studied. Parenchyma is the main cell type of the bark (50%) followed by fibres (27.9%), rays (12.1%), sieve tubes (2.7%), and sclereids (7.3%). The cell type proportions vary significantly within the tree, i.e., parenchyma, ray and sclereid proportions decrease, fibre and sieve tube proportions increase towards the top of the tree.