Tanning Agent Research Articles

Separation of Leather, Synthetic Leather and Polymers Using Handheld Laser-Induced Breakdown Spectroscopy.

Genuine leather is produced from animal skin by chemical tanning using chemical or vegetable agents, while synthetic leather is a combination of fabric and polymer. The replacement of natural leather by synthetic leather is becoming more difficult to identify. In this work, Laser Induced Breakdown Spectroscopy (LIBS) is evaluated to separate between very similar materials: leather, synthetic leather, and polymers. LIBS is now widely employed to provide a specific fingerprint from the different materials. Animal leathers processed with vegetable, chromium, or titanium tanning were analyzed together with polymers and synthetic leather from different origins. The spectra exhibited typical signatures from the tanning agents (Cr, Ti, Al) and the dyes and pigments, but also from polymer characteristic bands. The principal factor analysis allowed to discriminate between four main groups of samples representing the tanning processes and the polymer or synthetic leather character.

Facile synthesis of a new eco-friendly epoxy-modified oligomeric chitosan-based chrome-free tanning agent towards sustainable processing of functional leather

To reduce the contamination of Cr6+ and dyes from tannery wastewater, a chromium-free tanning agent with rich terminal epoxy groups (COS-GTE) was synthesized using oligomeric chitosan (COS) and glycerol triglycidyl ether (GTE). The structural characteristics and application performance of prepared COS–GTE were investigated by FTIR NMR, GPC, SEM, adsorption properties of fatliquor and dyes, and other analysis techniques. The application results indicated that the shrinkage temperature of finished leather tanned with COS–GTE can reach 83.5 °C. Compared with traditional tanning materials (F-90 and TWS), the finished leather had better mechanical properties (tear strength of 47.410 N/mm2) and yellowing resistance. Moreover, the natural skin modified with COS–GTE showed excellent antimicrobial properties against Escherichia coli, Staphylococcus aureus, Aspergillus flavus, and Aspergillus niger. Especially, the finished COS-GTE tanned leather had a high absorption rate of fatliquor (69.27 %) and dyes (X = 93.21 %), which is beneficial for reducing comprehensive wastewater pollution. The research revealed that the COS–GTE not only can be considered a new biomass material to solve the problem of chromium and dye contamination in the leather industry but also endows leathers with a unique antimicrobial function to extend product protection and service time.

APPLICATION OF ACACIA TANNINS IN ELASTIC LEATHER MATERIALS PRODUCTION TECHNOLOGY

An IR-spectroscopic study of the interaction of collagen with blackwood acacia (acacia melanoxylon) tannins and its use for tanning and filling semi-finished leather products in the production of elastic leathers for shoe uppers was conducted. The analysis of IR spectra of the interaction of the chrome tanning collagen products dermis with the acacia extract tannins can indicate the intermolecular ionic bonds formation and a hydrogen bonds dense network building-up with the amino groups of collagen and phenolic and carbonyl groups of the plant extract tannins. The following reagents were used for the semi-finished product tanning: sodium chloride TU 9192-069-00200009527-98, formic and sulfuric acids according to DSTU GOST 1706-78 and DSTU GOST 2184:2018, and sodium carbonate ISO 6353-2-83. Blackwood acacia extract together with the synthesis product of 2-naphtholsulfonic acid with dioxydiphenylsulfone as synthetic tanning agent BNS TU 17-06-165-89 were used to fill the tanned semi-finished product. The application of BNS TU 17-06-165-89 syntan in the process of finishing and filling of chrome tanned semi-finished leather product after catting it into thin slices with a thickness of 1.4 mm together with acacia extract tannins ensures an increase in its diffusion into the structure and provides a process duration reduction. The use of acacia extract tannins in the production technology of elastic hides makes it possible to obtain a filled-greased semi-finished product with increased physical and chemical properties: porosity, volumetric yield, air permeability by 21, 37, 86%, respectively, compared to the chrome tanning semi-finished product. The obtained results give the grounds for recommendation the use of acacia extract tannins in the wide range of elastic leathers production technologies.

Eco-Friendly Valorization and Utilization of Plant Waste as a Source of Tannin for Leather Tanning

In the present study, bark, which is the waste part of a tree, was utilized as a source of tannin for leather tanning after its value addition. The barks of Acacia nilotica L. and Eucalyptus globulus, which are abundantly available in Pakistan, were selected in this study. Different extraction techniques including mechanical, soxhlet, reflux and ultrasonic extraction were used for the extraction of tannin from the selected barks. The medium of extraction included aqueous as well as different solvent mixtures in different ratios. The solvent mixtures used in this study were methanol-water and acetone–water. The methanol–water ratio was kept (50:50) and the acetone–water ratio was maintained at (50:50 and 70:30). In the first step, the process of extraction was optimized for solvent mixtures and extraction time by taking a fixed dose (5 g) of each bark and a fixed volume of each extracting solvent mixture (150 mL). The total phenolic contents (TPC) of the bark extracts were determined by colorimetric assay (as mg GAE/g bark), taking gallic acid as the reference standard. The tannin contents (TC) of the bark extracts were determined by using the standard hide powder method (SLC 117). It was concluded that among the different extraction techniques, and among the solvent mixtures acetone–water in ratio (70:30), ultrasonic extraction resulted in maximum extraction of tannin (196.1 and 125.2 mg/g), respectively for A. nilotica and E. globulus. FTIR analyses of the dried extracts obtained from both barks were compared with FTIR of the most commonly used commercial vegetable tanning agent in the leather industry, i.e., mimosa. Results were comparable, which confirmed the presence of condensed tannin in both barks. The extracted tannin was applied on a pickle and wet blue leather to evaluate its tanning and re-tanning capability. Mimosa, the most abundantly used vegetable tanning material in the leather industry, was applied as a reference standard on the same pickle and wet blue leather for comparison. Different physical properties, such as leather shrinkage temperature, leather softness, tensile strength, percent elongation and breaking strength, were measured to evaluate the tanning efficacy of the extracted tannins. The results showed that tannin obtained from A. nilotica showed comparable physical properties to those of mimosa. It was concluded from the results that tannin obtained from locally available bark, i.e., A. nilotica, can be utilized as a vegetable tanning agent for the leather industry.

Effective and cleaner Zr (IV) tanning process based on the inert-surface modification of skin collagen by PEGylated epoxy copolymers

Zirconium tanning agent, which is mainly composed of low-toxic tetravalent zirconium (Zr4+) salts, has been considered the most promising eco-friendly tanning agent for leather manufacturing, due to its comparable tanning performance with trivalent chrome. However, in the initial penetration stage of the zirconium tanning process, macromolecular multinuclear complexes are commonly formed because of the rapid coordination between hydrated Zr4+, which can easily cross-link with active groups of neighboring collagen fibers and thus block subsequently even penetration of zirconium tanning agents, resulting in surface over-tanning and ununiform tanning effects. Herein, to address the aforementioned issues of conventional zirconium tanning, inert-surface modification of collagen fibers was proposed by using PEGylated epoxy copolymers (PEGMA-co-GMA, defined as PPG) to pretreat bated hide, based on the covalent reactions and hydrogen-bond interactions of PPG with amino and carboxyl groups on collagen fibers, respectively. After modification, the surface reactivity of skin collagen was significantly reduced, which was able to delay the cross-linking interactions with zirconium tanning agents and thus promote uniform penetration. Simultaneously, the extra hydroxyls produced from the ring-open reactions of epoxy groups could also mitigate the excessive coordinated complexation of hydrated Zr4+, leading to efficient penetration of zirconium tanning agents. Compared with conventional zirconium tanning, research results showed that this inert-surface modification strategy could comprehensively improve the overall leather performance with both efficient and uniform tanning effects. Moreover, the resultant leather qualities, including thermal stability, physical and mechanical properties, and organoleptic properties, are very comparable with chrome-tanned leather. In addition, attributing to the reaction between collagen amino and PPG, the use of sodium chloride was avoided, resulting in a cleaner salt-free pickling process. Altogether, this inert-surface modification strategy represents a significant step forward for effective and cleaner tanning technology, which will accelerate the wide application of Zr(IV) in place of traditional chrome tanning agents.

Sustainable leather making — An amphoteric organic chrome-free tanning agents based on recycling waste leather

Currently, globally, 90 % of the tannery is still tanned by using chrome, resulting in chromium-containing wastewater and chromium-containing solid waste that will cause serious harm to the environment. Under the pressure of environmental protection, on the one hand, the leather manufacturing industry should to dispose the current problem of chromium pollution, especially chromium-containing solid waste (chromium-containing waste leather (CCWL)), on the other hand, to popularize chrome-free tanning agent. Organic chrome-free tanning agents are the way forward for chrome-free tanning agents. However, organic chrome-free tanning agents exhibit several limitations with respect to their preparation and applications: The preparation process is not eco-friendly, and physicochemical properties of tanned crust leather are poor. More importantly, the leather tanned by an organic chrome-free tanning agent has low absorptivity of traditional anionic wet finishing materials, resulting in high total dissolved solids in tannery wastewater, which increased the difficulty of tannery wastewater treatment, and posed a potential threat to the environment. In this study, collagen polypeptide (CP) was extracted by using in situ dechromization and industrial trypsin from CCWL, followed by modification with ethylene glycol diglycidyl ether (EGDE) to obtain an epoxy-terminated, biomass-based, amphoteric organic, chrome-free tanning agent (CP-EGDE) with a high isoelectric point of 5.16, and an epoxy value of 0.316 mol/100 g. CP-EGDE can be applied in the pickling-free and salt-free tanning processes to prepare wet white leather and the tannery wastewater with good degradability. The shrinkage temperature (Ts = 84.9 °C), grain flatness, fullness, softness, yellowing resistance, mechanical properties, absorptivity of traditional anionic fatliquor (88.4 %) and dyes (95.3 %) of CP-EGDE tanned leather exceeded those of commercial organic chrome-free tanning agents. This research considered both environmental protection and leather quality, especially greatly improving the absorptivity of traditional anionic wet finishing materials. CP-EGDE is expected to replace chrome tanning agents and has good application prospects.

The use of gambier as a tanner for fur-tanned rabbit skin

Rabbit fur skin is an exotic skin group and a by-product of slaughtering animal houses. The tanning process is a process for processing. This vegetable tanning can be used as vegetable tanning materials derived from materials obtained from nature. examples of vegetable tanners are gambier and mimosa. The material used for research was rabbit fur 15 pieces and gambier. The research used in this experiment was a completely randomized design with 5 treatments and 3 replications, and there were significant influences would be tested by Duncan’s Multiple Range Test Method. The treatment of this research used mimosa 4% (T0), gambier 3% (T1), 4% (T2), 5% (T3) dan 6% (T4). The result showed that using gambier as tanning material has a significant effect on tensile strength, tear strength, thickness, and flexibility. The best result of this research was T4 using 6% of gambier as a tanning agent. The tanned skin had 34,43 N/mm2 tensile strength, 8,25 Kg/cm, tear strength of 2,33 mm thickness, and 77,09% flexibility. The conclusion of this research is gambier can be added as a tanning agent for rabbit fur and gives good quality.

Strategical development of chrome-free tanning agent by integrating layered double hydroxide with starch derivatives

The development of sustainable and eco-friendly leather industry requires green tanning agents because of unbounded chromium (easily converted into hazardous Cr-VI) in chrome tanned leather. In this study, a chrome-free tanning agent (OS-LDHs) was established by integrating layered double hydroxide (magnesium aluminum zirconium hydrotalcite, LDHs) with starch derivatives. A series of oxidized starch (OS) were prepared as masking agents for LDHs tanning process. Among them, the weight-average molecular weight (Mw) of 1685 g/mol could be reached, which will promise the well-distribution of OS. The SEM and EDS analysis confirmed the uniform penetration of OS-LDHs, avoiding accumulation on the surface of crust leather. Notably, leather tanned by OS-LDHs achieved shrinkage temperature of 66.7 °C, porosity of 75.51 % and tear strength of 66.7 N/mm. Not only the hydrogen bond but also the coordination between NH2, COOH in collagen and OS-2-LDHs improved the thermal stability of leather without destroying the collagen triple helix.

Techno-Economic Evaluation of Chromium Recovery Pilot Plant Installed at Kasur Tanneries Complex, Pakistan

Chromium metal is widely used as a tanning agent worldwide. The process called chrome-tanning is accomplished in three steps: Pickling, Tanning and Basification1 (Pakistan Tanners Association). Chromium sulfate is the most widely used chemical in this process. Approximately, 60-70 percent of chromium sulfate applied is taken up by the hides and skins, while its 30 to 40 percent remains un-used and is discharged as a component of wastewater into natural water bodies such as rivers, streams, etc., which has adverse environmental impacts on living organisms particularly to humans and animals [Weitz and Luxenberg (n.d.)], and water animals such as fish [Eisler (1986)]. The diseases especially encountered in humans, are of nervous disorders. The pollution from tanneries effluent particularly their chromium component has formed the basis that many developed countries have banned tanning on their soils. Chrome tanned leather, being the need of people all over the world, has the edge that its manufacture cannot be stopped. This has given some economic advantage to some developing countries including Pakistan to manufacture leather and export it to the developed countries. To sustain, different methods have been developed to recover chromium from the tannery effluents before their drainage in the natural water bodies. A few examples of these methods are High Chrome Exhaustion, Direct Recycling of the Spent Tanning Float and Chrome Recovery and Reuse [Arrafay Labs (2003)].

Application of an Integrated System of Thermal Pressure Hydrolysis/Membrane Techniques to Recover Chromium from Tannery Waste for Reuse in Hide Tanning Processes.

This paper presents the results of research on a new method of chromium recovery from solid waste generated during the tanning of raw hides. In the first stage, the shredded mixture of useless leather scraps is decomposed through thermal pressure hydrolysis (TPH) in nitric acid in appropriate process conditions. Then, the liquid product of this process (hydrolysate) is fractionated using membrane separation techniques. The microfiltration (MF) process enables the initial purification of the hydrolysate by concentrating the organic matter. On the other hand, the nanofiltration (NF) process enables a three-fold concentration of total chromium in the pre-purified hydrolysate. The total chromium concentrate prepared in the above manner was successfully used in the model tanning processes. These processes were carried out on pickled bovine hides, using a mixture of a commercial chromium tanning agent and chromium concentrate after nanofiltration. The reference sample was bovine hide traditionally tanned with a commercial chromium tanning agent. Based on the results of the physical and chemical analyses, it was found that the properties of hides tanned using chromium recovered from waste are similar to those of hides tanned traditionally using a commercially available chromium tanning agent. The industrial implementation of the developed tannery waste valorisation technology would enable transition from a linear economy to circular economy.

A novel synergistic covalence and complexation bridging strategy based on multi-functional biomass-derived aldehydes and Al(III) for engineering high-quality eco-leather

To get rid of the chrome pollution faced by the leather industry, we explored a novel engineering high-quality eco-leather technology based on the synergistic interactions between biomass-based aldehydes and Al(III). Firstly, dialdehyde xanthan gum (DXG) was prepared to covalently crosslink with the collagen fibers (CFs) via Schiff-base linkages under alkaline conditions, endowing the leather with a shrinkage temperature (Ts) of 80 °C and opening channels for the subsequent penetration of Al species (AL). Secondly, and for this latter purpose, the DXG-tanned leather was acidified to release part of the DXG from the leather according to the dynamic nature of the Schiff-base. Containing suitable oxygen-containing groups (OGs) with excellent complexation capabilities, the released DXG served as masking agents for AL, facilitating the penetration of AL into the inner CFs network for further complexation crosslinking. Consequently, a denser crosslinking network was constructed in the leather, and the crust leather exhibited higher Ts (82.2 °C), improved mechanical (tensile strength: 13.4 N/mm2, tear strength: 53.3 N/mm) and organoleptic properties than those of the DXG crust or AL crust leathers. This demonstrates that this synergistic covalence and complexation bridging strategy is a sustainable option to substitute highly restricted chrome tanning agent for eco-leather production.

Pyrolysis gas chromatography mass spectrometry: A promising tool for disclosing metal-free tanning agents used in leather industry

Leather represents the principal industrial product derived from the skin of animals. Leather manufacturing has evolved from artisanal practice, making use of vegetable tannins, to industrial production, today mostly based on chromium salts. Chromium tanning accounts for the most efficient and affordable process available on the market, but the environmental pressure caused by heavy metal pollution has pushed towards the development of Metal-Free leather tanning agents. This paper aims at highlighting the potentialities and limits of analytical pyrolysis to characterise metal-free leather samples and to identify the tanning agents. To this aim, thirty-three bovine split leather samples tanned with various metal-free tanning agents (constituted by single or combined formulations of GRANOFIN® F90, glutaraldehyde, tetrakis(hydroxymethyl)phosphonium sulphate, oxazolidine and three different synthetic tannins), provided by bovine split suppliers (Tuscany, Italy) were analysed by flash Pyrolysis coupled with Gas Chromatography - Mass Spectrometry (Py-GC-MS). For most of the tanning formulations, Py-GC-MS was able to determine pyrolytic markers in reference materials, intermediates (wet-white metal-free and metal-free crust) and end-products (metal-free final products). Evolved Gas Analysis coupled with Mass Spectrometry (EGA-MS) was used to evaluate, from the molecular point of view, the thermodegradative profiles of metal-free leathers and compare them with that of chromium tanned leather.

An eco-friendly metal-less tanning process: Zr-based metal-organic frameworks as novel chrome-free tanning agent

Chrome-free tanning agent is of great significance because it can eliminate the notable environmental pollution of chrome tanning. Metal-organic frameworks (MOFs) are the products of the desired combination of metal ions and organic ligands, which make them the born self-masking tanning agent. Herein, a series of Zr-MOFs were prepared by a solvothermal method, and then applied in leather tanning process. Among the Zr-MOFs family, UiO-66 tanned leather exhibited the highest shrinkage temperature (Ts) of 75.3 °C. Meanwhile, the smaller particle size and self-masking structure of Zr-MOFs allowed for the uniform distribution in collagen fibers matrix, thus giving improved physical-mechanical and organoleptic properties. It was noted that 80% metal usage reduced could be achieved with Zr-MOF as tanning agent comparing with conventional zirconium sulfate. It was found that Zr4+ of Zr-MOFs could mainly coordinate with -COOH and -NH2 groups in collagen fibers to form a stable cross-linked structure. In addition, the BOD5/COD value (>0.3) of Zr-MOF tanning waste liquor indicated good biodegradability, further confirming the eco-friendly metal-less tanning process. All results indicate that the proposed Zr-MOFs will promote the eco-friendly metal-less tanning process and open a new chapter for the chrome-free tannage.

Identification of surface dyeing agents of two bookbinding leathers from 19th‐century Qajar, Iran, using LC–MS, μXRF and FTIR spectroscopy

AbstractIdentifying tanning and dyeing agents of historical leathers is one of the less studied subjects. Therefore, this study aims to distinguish the surface dyeing agent of historical leathers along with the tanning agents. It helps to better understand the leather‐making process of past centuries. For this purpose, two Iranian historical bookbinding leathers belonging to the Qajar era were investigated. The tannins were examined by ferric spot test and ATR‐FTIR spectroscopy after being extracted from the leather corium layer. ATR‐FTIR and μXRF spectroscopy were also used to study the characteristics of the leathers' surface, in both grain and corium layers. LC–MS was also used to analyze the extracts taken from the surface of the leather samples. The results showed the corium layer of leathers has a significant number of hydrolysable tannins, especially gallotannins, as tanning agents. The characteristics of their FTIR spectra are significantly similar to those of sumac. LC–MS results showed the presence of ellagic acid, as an indicator analyte, on the surface of the leathers. It indicates that tannin‐rich plants, such as oak, have been used for dyeing these leathers. Investigation of the structural properties of the grain and corium layers also revealed the accumulation of copper and iron on the surface of the leathers. Accordingly, copper and iron, which reacted with tannins to give a black color, were the main dyeing factor used in both historical leather samples.

Leather buffing dust in brick production: Solid waste management in tanneries

In leather processing, the generation of buffing dust is an indispensable solid waste. It contains chromium, synthetic oil, dyestuffs, and tanning agents. Management of buffing dust has become a great challenge for the leather industry. This study aims to use buffing dust in brick production and examine the effects of incorporating buffing dust into the physicomechanical, environmental, and morphological properties of produced bricks. In this experiment, bricks were produced conventionally by mixing buffing dust in different ratios ranging from 0% to 12% (wt.) with the clay, and the bricks were fired in a kiln at 1000 °C. Results indicate that 4% buffing dust incorporated bricks showed the maximum compressive strength (12.02 MPa), as well as other engineering properties - water absorption, weight loss on ignition, area shrinkage, bulk density, efflorescence test results - were also in the acceptable range according to ASTM and Bangladesh Standards. Scanning Electron Microscope images imply that buffing dust played an important role in the structure of fired bricks. The NEN 7345 and TCLP leaching tests of fired bricks showed that the leached amount of heavy metals was insignificant and far below the permissible limit. Thus using buffing dust incorporated bricks is quite feasible and will reduce environmental pollution as well.

Sustainable utilization of corn starch resources: A novel soluble starch-based functional chrome-free tanning agent for the eco-leather production

Tanning is an important procedure in the leather making process. Currently, chrome tanning is still mainly used for leather processing both domestically and internationally, resulting in chrome-containing wastewater, chrome-containing sludge and chrome-containing solid waste. In this study, a new soluble starch-based chrome-free tanning agent (SCT) with abundant terminal epoxy groups was synthesized by grafting triglycidyl isocyanurate (TGIC) onto soluble starch (ST). In addition, structure characterization and performance test of the obtained SCT tanning agent were conducted, which was subsequently used as a chrome-free tanning agent for ecological leather processing and manufacturing. NMR and FTIR spectra revealed typical peaks for the TGIC functional groups in the SCT molecular structure, indicating that ST was successfully crosslinked with TGIC. After the prepared SCT was used for the chrome-free tanning process of sheepskin, the moisture and heat stability of the tanned leather were significantly increased, and the shrinkage temperature (Ts) exceeded 84.2 °C. Furthermore, SCT-tanned leather exhibited good collagen fiber dispersion, yellowing resistance, mechanical properties, softness and thickening compared with those of commercially available chrome-free tanning agent. Therefore, keeping with the trend of eco-leather processing development, SCT as a green chrome-free tanning agent demonstrates broad application prospects for the sustainable industrial processing of leather.

Evaluation of DNA-Damaging Effects Induced by Different Tanning Agents Used in the Processing of Natural Leather-Pilot Study on HepG2 Cell Line.

For a long time, the production and processing of cowhide was based on the use of chrome tanning. However, the growing problem with chromium waste and its negative impact on human health and the environment prompted the search for more environmentally friendly processes such as vegetable tanning or aldehyde tanning. In the present study, we investigated the DNA-damaging effects induced in HepG2 cells after 24 h exposure to leather samples (cut into 1 × 1 cm2 rectangles) processed with different tanning agents. Our main objective was to determine which tanning procedure resulted in the highest DNA instability. The extent of treatment-induced DNA damage was determined using the alkaline comet assay. All tanning processes used in leather processing caused primary DNA damage in HepG2 cells compared to untreated cells. The effects measured in the exposed cells indicate that the leaching of potentially genotoxic chemicals from the same surface is variable and was highest after vegetable tanning, followed by synthetic tanning and chrome tanning. These results could be due to the complex composition of the vegetable and synthetic tanning agents. Despite all limitations, these preliminary results could be useful to gain a general insight into the genotoxic potential of the processes used in the processing of natural leather and to plan future experiments with more specific cell or tissue models.

Superhydrophobic Modification of Collagen Fiber

Tanning is considered to be the crosslinking reaction between collagen fibers and tanning agents, and a majority of tanning reactions result in suppressed water absorption and enhanced hydrophobicity of leather. However, extensive use of tanning agents may bring a burden to the environment. Herein, to facilitate a sustainable leather manufacturing industry, we propose a revolutionary strategy of “tanning” without tanning agents. Based on this strategy, superhydrophobic collagen fibers (FAS-CFs) were fabricated through dehydration, followed by superhydrophobic modification. Dehydration aimed to eliminate the “sticky” effect of water on collagen fiber to obtain a dispersed hierarchical structure. Superhydrophobic modification not only dispersed and stabilized the fiber structures, but also protected the fiber dispersity from water immersion. Compared with chrome-tanned collagen fibers (Cr-CFs) and glutaraldehyde-tanned collagen fibers (G-CFs), FAS-CFs showed higher hydrophobicity, lower water absorption, and superior mechanical properties. Meanwhile, FAS-CFs exhibited a high thermal denaturation temperature of 92.5°C and retained their original shape after being heated to 100°C. Therefore, our proposed strategy is expected to be a potential substitute for conventional tanning and might contribute to cleaner and sustainable leather manufacturing.

In vitro anti-melanoma effect of polyphenolic compounds

Objective: To evaluate the effects of phenolic acids (caffeic, ferulic, and coumaric acids) and flavones (luteolin and apigenin) on the proliferation and melanogenesis in murine melanoma B16-F10 cells. Methods: Cell proliferation was determined after 24 and 48 hours of incubation using MTT assay. The effects of these tested compounds on cell cycle progression were analyzed by flow cytometry. Moreover, the melanin content and tyrosinase activity were measured spectrophotometrically at 475 nm. Results: Luteolin and apigenin exhibited significant anti-proliferative activity against B16-F10 cells, while caffeic, ferulic, and coumaric acids induced slight inhibition after 24 and 48 hours of incubation. The tested compounds disturbed cell cycle progression of B16-F10, by a subsequent decrease in G1 and arrested cycle progression in either G1/S or G2/M phase. Furthermore, apigenin provoked an increase in melanin content of B16-F10 cells. In contrast, luteolin, caffeic, ferulic and coumaric acids induced a decrease in melanin content of B16-F10 cells by inhibiting tyrosinase activity. Conclusions: These active polyphenols may be used as skin whitening agents or natural tanning agents to treat skin pigmentation disorders.

Application of Indigenous Plant-Based Vegetable Tanning Agent Extracted from Xylocarpus granatum in Semi-Chrome and Chrome Retanned Leather Production

Environmental issues are nowadays the prime concern worldwide for leather industries due to chrome containing solid and liquid wastes generated from the tannery. Therefore, experts are being encouraged in exploring alternative tanning agents. This study aimed at applying a novel vegetable tanning agent extracted from Xylocarpus granatum barks for the production of semi-chrome (SC) and chrome retanned (CR) leathers to reduce chromium use. Characterization of the SC and CR leathers was performed by Fourier Transform Infrared (FTIR) spectroscopy which revealed prominent tanning activity of the extracted tannins. The tanned leathers exhibited shrinkage temperatures of 112˚C for SC and 103˚C for CR leathers. The physicomechanical properties were found as tensile strength >230 kg/cm2, tear strength >30 kg/cm, grain cracking load >20 kg, distention at grain crack >7 mm, ball bursting load >38 kg, and distention at ball bursting >12mm that was comparatively acceptable according to UNIDO standard for shoe upper leathers.