Leather Conservation Science

Many objects of culture heritage, comprised of leather, need to receive the right treatment to be restored and to elongate their lifespan. Determination of the degradation degree and even better the type of the degradation is a crucial knowledge for the way of subsequent conservation, exhibition and long-term storage. Collagen based materials are very sensitive to the deterioration and undergo, mainly hydrolysis and oxidation. Namely acid hydrolysis and photooxidation are the most often causes of the disintegration of leather. Contrary to the leather investigation, a few studies dedicated to parchment described some typical features of hydrolysis, oxidation and gelatinization observed applying Attenuated Total Reflection Fourier-Transform Infrared spectroscopy (ATR-FTIR) which is widely used in collagen degradation type research. Except of the collagen secondary structure, followed by IR spectroscopy, we determined the shrinkage temperature of the collagen substrate by Micro Hot Tab...

The increasing global pressure for sustainable agricultural intensification has catalyzed a shift towards eco-friendly inputs, with plant biostimulants emerging as a pivotal tool. These substances, distinct from fertilizers, enhance crop growth, stress resilience, and yield by stimulating natural processes. This review comprehensively explores the nature and primary categories of plant biostimulants, including seaweed extracts, humic and fulvic acids, protein hydrolysates, and beneficial microorganisms.
It synthesizes the scientific evidence underpinning their multifaceted benefits, such as improved nutrient use efficiency, enhanced root development, and increased tolerance to abiotic stresses like drought and salinity. Focusing on the Ethiopian agricultural context, the paper critically assesses the current application status, identifying significant challenges. These include limited awareness, insufficient local research and production capacity, high import costs, and underdeveloped regulatory
frameworks. Despite these hurdles, the immense potential of iostimulants to address soil degradation, climate variability, and food insecurity in Ethiopia is undeniable. The integration of plant biostimulants into the Ethiopian agricultural landscape represents more than just an adoption of a new technology; it signifies a paradigm shift towards ecological intensification. While the current application is nascent, constrained by
knowledge gaps and infrastructural limitations, the alignment of biostimulants with the nation's goals for climate resilience and food sovereignty is profound. A concerted effort spearheaded by public-private partnerships is required to foster local research for developing tailored products from indigenous resources, establish clear regulatory
pathways, and launch widespread farmer education programs. By strategically embracing biostimulants, Ethiopia can harness nature's own tools to rejuvenate its soils, buffer its crops against an increasingly erratic climate, and secure a productive and sustainable agricultural future for generations to come.

In continuation of part IV, this part deals with the colour tests, free sugars and phenolic agtycones of 28 plants (Lauraceae to Meliaceae). A detailed discussion of each plant is given, dealing with the results obtained by us and those given in literature. The present study is a continuation of the previous reports searching for plants containing tannins and flavonoids (1, 2). It covers those plants belonging to the families Lauraceae to Meliaceae. Emphesis was also made on tests specific for tannins and flavonoids as well as paper chromatographic analysis of the free sugars and phenolic agtycones. This study contains the well known family Legurninosae which is rich in tanniniferous plants. Among the barks of the plants of this family belong mimosa (Acacia mearnsii), babul (A. arabica) and avaram (Cassia auriculata), the woods of some plants are also well known tanning materials e.g. catechu or Burma cutch {Acacia catechu} and chestnut (Castanea sativa); moreover the pods may be a rich source for tannins in this family as those of divi-divi (Caesalpinia coriaria), algorobilla (C brevifolia), tara {C spinosa) and sant {Acacia arabica); the Egyptian species are known as A. nilotica (3). Besides, other plants belonging to the same family are recorded as containing over 10% tannins (4); among these are a number of Acacia, Albizzia, Bauhinia, Cassia, Piptadenia, Pterocarpus and others. In this study 28 plants are studied and each plant shall be discussed in details hereafter. RESULTS AND DISCUSSION Cinnamomum gtanduli f enLm { Lauraceae } The leaves and bark of this plant were found to contain condensed tannins. Protocatechuic acid was detected in both the leaves and bark, while caffeic acid was only identified in the bark. This plant has not been recorded to contain tannins.

Excavations carried out at the Yenikapı quarter of Istanbul under the Directorate of the Istanbul Archeological Museum between 2004-2013 and have brought the historical importance of the port to light. During the salvage excavations in Yenikapı, hundreds of leather sandals and leather objects from the Byzantine period have been uncovered. The aim of this study is to determine both tanning and coloring materials of eight leather objects belonging to the Byzantine period and physicochemical characterize the leather structure. A complementary analytical approach has been used to characterize leather objects. The ATR-FTIR analysis revealed that the leather objects were tanned with vegetable tannins (gallotanins, condensed tannins and hydrolyzable tannins). By HPLC-DAD analysis, it is known that tannin dye plants were used to color the leather (Quercus infectoria or Quercus ithaburensis). The EDS analysis result showed the possible use of cupric sulfate (CuSO 4) for preliminary preparation before tanning leathers during the Byzantine period. In addition, SEM was used for visual assessment of the degree of deterioration of leathers. Based on the EDX analysis, biological deterioration factors and changes in the element ratio have shown that the leather objects deteriorate. In addition, pH, moisture content and CIE* Lab values show that there is a deterioration in the structure of leathers under the sea. The study will sheds light to leather conservation studies.

In this study six different commercial vegetable tannins were analysed by ultraviolet spectroscopy and multivariate analysis. In addition, also it was determinated a specific absorptivity and quantified the total polyphenols and tannin content of each extract by filter and Folin Ciocalteu methods, respectively. The lowest values of specific absorptivity were for extracts of condensed tannins and the highest for the hydrolysable tannins. At analysis of total polyphenols, the condensed tannins showed the highest percentage, 90% and 80% for the quebracho and mimosa, respectively. Hydrolysable tannins were in the range 60-67%. In the evaluation of tanning percentage, the quebracho, chestnut and mimosa presented a percentage around 80%, followed by valonea, tara and myrobalan, 74, 56 and 41%, respectively. At multivariate analysis, a well-defined separation can be seen through both principal component analysis (PCA) and hierarchical cluster analysis (HCA), between condensed (quebracho and mimosa) and hydrolysable (valonea, chestnut, myrobalan, and tara) tannins. In hydrolysable tannins, it was also possible to observe the formation of two different subgroups between samples of chestnut and valonea and between samples of tara and myrobalan. Of all samples analysed, the chestnut and valonea showed the greatest similarity, indicating that these extracts contain equivalent chemical compositions and structure and, therefore, have similar properties.

In the present study, the tannins from stem and root barks of Tessmannia burttii Harms (Caesalpiniaceae), a plant species abundantly growing in Tanzania and other parts of Africa, were investigated for their suitability in hides tanning. Tannin powder was extracted at selected temperatures (30, 50 and 80°C) and the influence of each temperature on the crosslinking capacity was evaluated. The interaction mechanism between hide powder collagen and the tannins was studied by Differential Scanning Calorimetry (DSC), trinitrobenzensulfonic (TNBS) acid assay and amino acid hydrolysis methods. Extraction temperatures showed low influence on crosslinking capacity of the tannins. However, extract obtained at 50°C exhibited best performance in terms of gap size between T onset and T peak. The stem bark extract yield was higher than that from the root bark, but both were within the recommended ranges. The tannin content (61%) of T. burttii stem bark extract was above recommended value (10%), whereas its total phenolic content and total flavonoic content were found to be above that of commercial Acacia mearnsii tannin. The study of cross-linking parameters as a function of pH showed cross-linking to occur via a covalent mechanism at the basic amino groups. However, the bonds were not resistant to acid hydrolysis. The observed interaction mechanism indicated that tannins from stem and root barks of T. burttii belong to the condensed tannin, similar to A. mearnsii (black wattle), a commercial tannin source that was used in this study as a reference. Findings from this study depict that T. burttii extracts are auspicious eco-friendly alternative source of vegetable tannins to overcome the use of chromium salts in the leather industry.

This study was aimed to investigate the chemical composition of commercial tannins produced in Turkey mostly used by leatherworking. Tannin samples from pine bark, valonia, and gall nuts as well as ground sumac leaves were provided from the plant. It is well known that valonia, gall nuts, and sumac tannins compose of hydrolysable tannin whereas pine bark tannin consists of condensed tannins. Therefore methods of hydrolyzed and condensed tannins were applied in commercial samples. The methanolwater solubility of tannin samples was determined, after that total phenol content was assayed by spectrometrically in aqueous phase and ether phase. Amount of condensed tannin in the samples was determined by spectroscopical acid-butanol methods as well as stiasny number method gravimetrically. Content of gallotannin in samples was determined with Rhodanine Method; amount of ellagtannins was assayed with Nitrous Acid method. Functional group analysis of the tannin samples were investigated by FTIR instrument after compressing KBr pellets.

In this study, hydrolyzable tannins (commercial chestnut, valonea and tara extracts), condensed tannins (commercial quebracho and mimosa extracts) as well as calf leathers produced using these vegetable tanning agents were characterized by thermal decomposition methods using slow and high heating rates. Calf gelatin obtained by heating calf pelt in water at 70 ˚C was chosen as a reference material. Thermogravimetry/mass spectrometry (TG/MS) and pyrolysis-gas chromatography/mass spectrometry (Py-GC/MS) experiments were performed on the tannin and leather samples. The evolution profiles of the decomposition products as well as the thermal stability of tannins and leathers were studied by TG/MS. A net difference was observed in the thermal behavior of hydrolyzable and condensed tannins. The condensed tannins produced the highest char yield, while the hydrolyzable tara extract released the most volatile products. The tannins of higher reactivity produced more stable leathers as it results from their higher decomposition temperature. The composition of both vegetable tanned leathers and vegetable tanning agents was characterized by the pyrolysis product distribution measured by Py-GC/MS method. Resorcinol and its methylated derivative (orcinol) were found to be characteristic decomposition products for both condensed tannins, i.e. mimosa and quebracho. It was identified among the pyrolysis products of the mimosa and quebracho tanned leathers, as well. Characteristic decomposition product, a bisphenol derivative was identified among the pyrolyzates of hydrolyzable tannins and the leathers tanned with the hydrolyzable tannin agents.

Ancient vegetable tanned leathers and parchments are very complex materials in which both different manufacturing and deterioration processes make their study and chemical characterisation difficult. In this research, solid‐state nuclear magnetic resonance (NMR) spectroscopy was applied to identify different tannin families (condensed and hydrolysable) in historical leather objects such as bookbindings, wall upholsters, footwear and accessories, and military apparel. Furthermore, leather deterioration with special focus on collagen gelatinisation was investigated. A comparison with Fourier transform infrared (FTIR) spectroscopy and micro‐differential scanning calorimetry (micro‐DSC) was also performed to support the 13C CP‐MAS NMR findings and to point out the advantages and limitations of solid‐state NMR in analysing historical and archaeological leathers. A wide database of NMR and FTIR spectra of commercial tannins compounds was also collected in order to characterise historical ...

Unilateral nuclear magnetic resonance (NMR) and imaging thermal microscopy (imageMHT) were performed on newly obtained and artificially aged vegetable tanned leathers. Calf and sheep leathers tanned with vegetal extracts of mimosa bark, quebracho and chestnut wood were compared. Ageing was simulated by exposing the leather samples to heating at 70°C in controlled atmosphere at 30% relative humidity and irradiating them with 4000 lx in the visible light region for 8, 16, 32 and 64 days. Proton spin-lattice relaxation times T 1 and effective spin-spin relaxation times T 2eff were measured at room temperature and their trend variation compared with the corresponding variations of shrinkage temperature T s and total length of shrinkage interval measured by imageMHT. Newly obtained leather displayed different proton relaxation times and shrinkage temperatures depending on both the collagen origin and tannin type. Effective spin-spin relaxation values shown to be discriminative for collagen origin and sensitive to the cross-linking degree, whereas spin-lattice relaxation values were more sensitive to the tannin type. Both NMR relaxation times were sensitive to the changes in the water dynamics upon ageing due to the formation of collagen damaged intermediate states and shown a sudden change when the tannin matrix was depleted (e.g. de-tanning).

Leather is a complex material mostly consisting of a matrix of collagen, chemically stabilized by various tannins. This matrix, sooner or later undergoes alterations as a consequence of interactions between their structure and environment. A comprehensive study based on multiple chemical and physico-mechanical standard tests regarding leather samples which were artificially aged from 7 to 112 days has been made at 70°C. The behavior in artificial aging of calf leather samples tanned at pilot level with two different vegetal tannins, mimosa and quebracho, were investigated due to its’s similarity to the natural degradation of historical leather samples. Physico-mechanical characteristics of historical leather can be corelated with the high impact of degree of deterioration even though there are no standard regulations. To be able to choose the proper way to achieve compatibility with an appropriate material in the restoration-conservation process, multiple sample characteristic must ...

Tannins from the root bark of Quercus aegilops L. were extracted in two successive seasons and their astringency score and antioxidant potential were evaluated using bovine serum albumin (BSA) radial diffusion and 2,2-Diphenyl-1-Picrylhydrazyl (DPPH) assay methods respectively. The results revealed that the root bark of this oak species contained on average 11.39 %(w/w) tannins as gallic acid, of which about 79% are hydrolyzable (HT) and 21% condensed (CT) tannins with the former composed mainly of ellagitannins and much fewer gallotannins and free gallic acid. The results also revealed that the crude root bark powder and its purified tannins have astringency scores of 15.8 and 138.98 mg BSA/g respectively. The antioxidant potential was evaluated by DPPH assay and expressed as inhibition capacity (IC50) was 149.7 ppm and 19.24 ppm for the crude bark powder and its purified tannins respectively indicating the superior antioxidant potential of these tannins to that of ascorbic acid. The highly-antioxidant functional tea prepared from these tannins was clear and acceptable to tasters.

Tannins are natural polyphenolic compounds widely distributed in the plant kingdom in the leaves, bark, fruits, and other parts. ey have various biological functions in humans and animals and are used mainly in the pharmaceutical and cosmetic industries. e aim of this work was to isolate, extract, purify, and identify the tannins from the root bark of a common oak tree (Quercus aegilops L.) in Jordan and around the Mediterranean. e results showed that at least one form of ellagitannin (ellagic acid ester), quercitrin, afzelechin, valoneic acid, trigalloyl glucose, and catechin was identified in addition to two unidentified compounds. Results of this work can help in developing an ESI MS/MS search library for the constituents of the tannins of oak (Quercus aegilops L.) root bark.

One of the highlighted areas in the development of new materials is the generation of micro-and nanoparticles as drug carriers which allow the progress in formulations with the ability to release active agents in a controlled way. The proanthocyanidins (PAC) extracted from the bark of the Black Wattle have stood out for their biological activities. However, most polyflavonoids have some features which limit their application in the pharmaceutical field, such as light fastness, low bioavailability of active agents, and unpleasant taste. In this context, this study aims to present the synthesis and characterization of PAC-loaded lactic-co-glycolic acid (PLGA) microparticles obtained by the multiple emulsion method. The incorporation of PAC into PLGA was successfully achieved with PAC encapsulation efficiency around 73%. Spherical microparticles were obtained with a size distribution in the range of 0.6 to 2.4 μm. The presence of PAC modified the thermal properties of the PLGA matrix. The results of in vitro assays with Vero and T24 lineage celss showed that PLGA/PAC microparticles did not promote any effect on cell proliferation by MTT assay after 24 h. The novel Acacia mearnsii proanthocyanidin-loaded PLGA microparticles have potential for application in biological systems.

Chrome tanning industry is dominated globally owing to its high versatility in quality leather production. However, Environmental impacts of chromium have shifted the interest of present study to chrome-free options. Vegetable tannins have been proven to be environmentally safe producing good quality leather with comparable properties as that of chrome tanned leather. As such, scarcity of vegetable tannin supply demands characterization of noncommercialized sources locally available to feed local tanners. A simple extraction technique was used with different temperature 35, 50, & 85 o C. Leaves and barks from Anogessus leiocarpus grown in Sudan can produce commercially acceptable tannins in terms of extract yield, tannin, total phenolic, flavonoid contents, and crosslinking ability comparable to the extract from A. mearnsii barks, which is a worldwide known to be commercial tannin source. Results shows that temperature influences on extraction yields and tannin content was low, except for extract from Anogessus leiocarpus leaves that has shown an increase pattern with raise in temperature. Total phenolic and flavonoid content varied insignificantly with increase in extraction temperature, except for total flavonoid content of extract from Anogessus leiocarpus leaves that observed to be high at 50 o C (30.7). Variations in extract properties between extracts from plant parts studied in this work were significant. Tensile strength values of tanned skin with leaves extracts are higher than that tanned with barks. On the other hand, tanned skin with leaves extract produced greater skin elongation 40.6±0.35 compared to barks extract.

Leather making commonly use chromium salts to produce high quality products. However, the use of chromium salts is compromised by environmental safety concerns. Combination tanning using vegetable tanning coupled with aluminium sulphate can sustainably replace chrome tanning system. Adversely, the use of commercial aluminium sulphate poses economic burden that entails for cost effective sources. Abundance of kaolin on earth's crust with scarce utilization is an opportunity towards cost effective aluminium sulphate for tanning. Therefore, in the present work aluminium sulphate was prepared from kaolin and its performance for combination tanning was studied. Diffraction and vibrational spectroscopic studies were carried out to confirm the prepared aluminium sulphate. Combination tanning was carried out with mimosa vegetable tannins. Leathers tanned with the combination of aluminium sulphate from kaolin and mimosa vegetable tannin exhibited hydrothermal stability of up to 118 °C as compared to mimosa alone that showed the average of 80 °C. Physical strength characteristics met the standard norms. Fibers separation was good as confirmed through microscopic studies. The study provides a new insight on accomplishing self-sustenance through available resources and eco-friendly manufacturing system.

For a long time, R. coriaria has been used as a spice by grinding the dried fruits with salt, and it has also been widely used as a medicinal herb in traditional medicine for its athero protective effect and its ability to treat eye diseases, wounds, bowel disorders, ring worms and skin disorders. In addition, R. coriaria has recently shown to have hepatoprotective, anti-ischemic, antimicrobial as well as hypoglycemic, anti-tumor andhyperlipidemic effects. Volatile substances, flavonoids, tannins and xanthones have been reported from this plant. Due to its easy collection and the remarkable biological activities, R. coriaria has been used both as food and medicine in some parts of the world especially in Iran. Tannin extracted from Sumac possesses potent antimigratory activity. Sumac yield tannin a substance used in vegetable tanning. Effect of TANNIN (plant polyphenolic compound) on DNA extract from spinach has been studied. Tannin is extracted by using acetone extraction where DNA is extracted by ethanol precipitation. The effect of tannin on DNA was studied by using different concentrations (10% to 30%) of tannin. The Optical density (O.D.) values of DNA decreased over incubation time indicating reduction in density upon addition of tannin which may be protective by repairing DNA or preventing DNA damage.

The impossibility of using drugs for the health of farm animals leads to the search for alternative strategies with two purposes: to maintain animal health and safeguard human health. In this perspective, tannins have shown great promises. These phytocomplexes obtained from natural matrices with multiple health properties may be used as a feed supplement in chicken farms. In this work, we studied two tannin-based extracts (from Castanea sativa Mill. wood and from Schinopsis balansae Engl. Quebracho Colorado hardwood) with different chemical compositions on the spontaneous contractility on the isolated intestinal tissues of healthy chicken. The results showed that the chemical composition of the two phytocomplexes influenced the spontaneous intestinal contractility in different ways by regulating the tone and consequent progression of the food bolus. The chemical analysis of the two extracts revealed that Castanea sativa Mill. wood mainly contains hydrolysable tannins, while Schinops...