A Cork Cell Wall Approach To Swelling And Boiling

The bark of cork oak (Quercus suber L.) is mostly used for cork stopper production, whereas bark is undergoing a series of industrial procedures, boiling usually leading to changes in the characteristics of the tissue. Trees are traditionally grown under natural conditions; however, irrigation is now being used in plantations. These permanent water availability affects cork-oak development, while its effects on industrial procedures is unknown. This study provides a first insight into the behaviour of the cell walls of cork during the process of swelling and boiling when trees have been grown under irrigation, subject to a specific water regime. Cork tissue was analysed using environmental and scanning electron microscopy under three regimes: raw conditions; following immersion in water; and after boiling. Additionally, the radial expansion of samples was determined. The results showed greater cell-wall expansion in cork from the irrigated site than cork from the traditional rainfed plot, when hydrated for 24h. After boiling, the cell walls of the rainfed site were thinner than in the raw stage, in contrast to the irrigated cork. This study suggests that irrigation during cork-oak growth produces a higher capacity for adsorption, increasing cell-wall thickness from the raw stage to the boiling stage.

Histochemical Structure and Tensile Properties of Birch Cork Cell Walls

Tensile tests of birch cork were performed in the tangential direction. Birch cork in the wet state showed significantly higher extensibility and toughness than those in the oven-dried state. The histochemical structure of birch cork was investigated by microscopic observation and spectroscopic analysis. Birch cork cell walls showed a three-layered structure. In transmission electron micrographs, osmium tetroxide stained the outer and inner layers, whereas potassium permanganate stained the middle and inner layers. After chemical treatment to remove suberin and lignin, the outer and inner layers disappeared and Fourier-transformed infrared spectra showed the cellulose I pattern. Polarizing light micrographs indicated that molecular chains in the outer and inner layers were oriented perpendicular to suberin lamination, whereas those in the inner layer showed longitudinal orientation. These results suggested that the outer and inner layers mainly consist of suberin, whereas the middle layer and compound middle lamella consist of lignin, cellulose, and other polysaccharides. We hypothesized a hierarchical model of the birch cork cell wall. The lignified cell wall with helical arrangement of cellulose microfibrils is sandwiched between two suberized walls. Cellulose microfibrils in the middle layer act like a spring and bear tensile loads. In the wet state, water and cellulose in the compound middle lamella transfer tensile stress between cells. In the dried state, this stress-transferal system functions poorly and fewer cells bear stress. Suberin in the outer and inner layers prevents absolute drying to maintain mechanical properties of the bark and to bear tensile stress caused by trunk diameter growth.

Comparative Studies of Fraxinus Species from Korea Using Microscopic Characterization, Phytochemical Analysis, and Anti-Lipase Enzyme Activity

Fraxinus species belongs to the Oleaceae family, commonly known as Ash tree, and has been utilized as a folk medicine with various medicinal properties, including anti-obesity activity. The goal of the present study was to establish quality control parameters using microscopic characterization, phytochemical differentiation, and anti-lipase activity evaluation of five Fraxinus plants in Korea. Microscopic evaluation of the lower surface, petiole, and midrib of leaves, and stem bark showed discriminative anatomical characteristics, such as the stomatal index of the lower leaf surface; the number of sclerenchyma cells, and the diameter of parenchyma cells in the petiole and midrib; and the cork cell size and fiber frequency in the stem bark. Phytochemical analysis using high-performance liquid chromatography revealed the significant variation in the chemical profiles of the 12 major secondary metabolites among the samples. The orthogonal projections to latent structure-discrimination analysis efficiently differentiated each group belonging to each Fraxinus plant with the anatomical and quantification data. F. rhynchophylla and ligstroside showed the most potent anti-lipase activity among the plants and the 12 major metabolites, respectively. These findings could serve as the scientific criteria for the appropriate identification and establishment of standards for the use of Fraxinus species as medicinal plants.

Pharmacognostic studies of Morinda brevipes S. Y. Hu

DNA barcoding of ITS and psbA-trnH regions, histochemistry as well as thin layer chromatography (TLC) of Morinda brevipes S.Y. Hu were analyzed. Transverse section of root revealed the presence of cortex, xylem, cork cell, stone cells, and calcium oxalate sandy crystal. The lower epidermis cells showed many stoma in paracytic or inequality type. Spiral vessel and tiny calcium oxalate needle crystal usually appeared in the powder. TLC showed the presence of emodin in M. brevipes. Phytochemical studies revealed the existence of carbohydrates, saponins, tannins, flavones, anthraquinones, alkaloids and volatile oils. The ITS and psbAtrnH sequences were found for the first time which were submitted to NCBI to obtain the GenBank registration number. This study might play an important role in the identification, and utilization of M. brevipes for various purposes.

PHARMACOGNOSTIC STANDARDIZATION, PRELIMINARY PHYTOCHEMICAL SCREENING AND TLC FINGERPRINTING OF THE BARK OF CASCABELA THEVETIA L.

Objectives: In this study, systematic pharmacognostic study and preliminary phytochemical screening of the bark of Cascabela thevetia L. were carried out. Methods: The selected plant part was collected, processed and stored in an airtight container. From the bark different pharmacognostic studies like macroscopic and microscopic evaluation, physicochemical parameters, fluorescence analysis were done. Powdered bark was successively extracted by petroleum ether, chloroform, ethyl acetate, and methanol using a Soxhlet apparatus and finally macerated with the hydro-alcoholic solvent system (30:70). The preliminary phytochemical analysis and thin layer chromatography of the extracts were done to find the nature and number of the different phytoconstituents present. Results: Transverse microscopy reveals the presence of crystal oxalate, cork cell, starch granules, vascular bundle, phloem fiber, parenchyma cells, and collenchyma cells. Powder microscopy also showed the presence of cork cell, fiber and calcium oxalate crystal. Results obtained in different physicochemical analysis like total ash, acid insoluble ash, water soluble ash, alcohol-soluble extractive, water-soluble extractive, and moisture content were 8.67%, 0.83%, 5.33%, 4.53%, 12.27%, and 7.83% respectively. Phytochemical analysis showed the presence of alkaloid, flavonoid, triterpenoid, phytosterol, tannin, saponin, anthraquinone, carbohydrate and fatty acid in the different extracts. TLC (Thin Layer Chromatography) study revealed 4 spots in petroleum ether, chloroform, ethyl acetate, and methanol extracts and 3 spots in the Hydro-alcoholic extract with different solvent systems. Conclusion: The results obtained from the study will provide a reliable basis for identification, purity, and quality of the plant.

Ferulates and lignin structural composition in cork

The structure of lignin and suberin, and ferulic acid (FA) content in cork from Quercus suber L. were studied. Extractive-free cork (Cork), suberin, desuberized cork (Corksap), and milled-cork lignins (MCL) from Cork and Corksap were isolated. Suberin composition was determined by GC-MS/FID, whereas the polymers structure in Cork, Corksap, and MCL was studied by Py-TMAH and 2D-HSQC-NMR. Suberin contained 94.4% of aliphatics and 3.2% of phenolics, with 90% of ω-hydroxyacids and α,ω-diacids. FA represented 2.7% of the suberin monomers, overwhelmingly esterified to the cork matrix. Py-TMAH revealed significant FA amounts in all samples, with about 3% and 6% in cork and cork lignins, respectively. Py-TMAH and 2D-HSQC-NMR demonstrated that cork lignin is a G-lignin (>96% G units), with a structure dominated by β–O–4′ alkyl-aryl ether linkages (80% and 77% of all linkages in MCL and MCLsap, respectively), followed by phenylcoumarans (18% and 20% in MCL and MCLsap, respectively), and smaller amounts of resinols (ca. 2%) and dibenzodioxocins (1%). HSQC also revealed that cork lignin is heavily acylated (ca. 50%) exclusively at the side-chain γ-position. Ferulates possibly have an important function in the chemical assembly of cork cell walls with a cross-linking role between suberin, lignin and carbohydrates.