Molecular Structure of Gardenia Blue Pigments by Reaction of Genipin with Benzylamine and Amino Acids

Enzymatic synthesis of Vaccinium blue using vaccinoside as a bifunctional precursor

Since Tang dynasty in China, the fresh leaves of Vaccinium bracteatum (VBL) have been applied as natural pigment to produce black rice. However, detailed information on its biosynthetic mechanism still remained unclear. Following rice dyeing capacity assay, vaccinoside, one of iridoid glycosides, was identified as the key active compound. Increased methodical research demonstrated vaccinoside as a distinct bifunctional precursor, which could be catalyzed by polyphenol oxidase or β-glucosidase independently, followed by reaction with 15 amino acids to give blue pigments (VBPs; λmax 581-590 nm) of different hues. Two synthetic pathways of VBPs were proposed, using multiple techniques such as HPLC, HPSEC, UV-Vis spectrum and colorimeter as analysis tools. Black rice was interpreted to be prepared by cooking, using vaccinoside, intrinsic enzymes from fresh VBL and rice protein in combination. These findings promote the understanding of VBP formation mechanisms and provide an efficient method of producing novel Vaccinium blue pigments.

Expression of a thermostable glucose-stimulated β-glucosidase from a hot-spring metagenome and its promising application to produce gardenia blue

This study reports a thermostable glucose-stimulated β-glucosidase, BglY442, from hot-spring metagenomic data that was cloned and expressed in Escherichia coli BL21 (DE3). The molecular mass of recombinant BglY442 was 69.9 kDa and was used in the production of gardenia blue. The recombinant BglY442 showed its maximum activity at pH 6.0 and 75 °C, maintained 50 % activity at 70 °C for 36 h, presented over 90 % activity in a broad pH range and a wide range of pH stability. Moreover, BglY442 exhibited excellent tolerance toward methanol and ethanol. The specific activity of BglY442 was 235 U/mg at pH 6.0 and 75 °C with 10 mM pNPG as substrate. BglY442 activity increased by over fourfold with 2 M glucose or xylose. Specifically, the enzyme kinetics of BglY442 seem to be non-Michaelis-Menten kinetics or atypical kinetics because the Michaelis-Menten saturation kinetics were not observed with pNPG, oNPG or geniposide as substrates. Under optimum conditions, geniposide was dehydrated by BglY442 and reacted with nine amino acids respectively by the one-pot method. Only the Arg or Met derived pigments showed bright blue, and these two pigments had similar ultraviolet absorption spectra. The OD590 nm of GB was detected to be 1.06 after 24 h with the addition of Arg and 1.61 after 36 h with the addition of Met. The intermediate was elucidated and identified as ginipin. Molecular docking analysis indicated that the enzyme had a similar catalytic mechanism to the reported GH1 Bgls. BglY442 exhibited potential for gardenia blue production by the one-pot method. With outstanding thermostability and glucose tolerance, BglY442 should be considered a potential β-glucosidase in biotechnology applications.

Solvent-free strategies for developing latent fingermarks on paper: a review

With growing environmental concern and supply chain uncertainty, now is a fitting time to re-evaluate solvent-free methodologies in forensic chemistry processes. Here, this paper reviews solvent-free approaches for fingermark visualisation, including chemical fuming and vapour phase treatments, dry-transfer treatments, application of heat, and thermal paper specific treatments. After providing historical context, three objectives have been emphasised: identify feasible scenarios for implementing solvent-free methods; showcase the effectiveness of solvent-free methods relative to their nearest solution-based equivalent; and estimate the technological readiness level of each method discussed. Having reviewed the literature, dry-transfer methods of developing latent fingermarks on paper were found to be the most promising and feasible solvent-free approaches for near-term implementation. Such methods make use of standard materials and equipment commonly found in forensic laboratories, are effective at fingermark visualisation, and mitigate most of the pressing issues pertaining to environmental concern and solvent scarcity.

Extended one-generation reproductive toxicity study evaluating gardenia blue in Sprague Dawley rats

Gardenia blue powder was administered at 0.5%, 2.5%, or 5.0% in feed to male and female Sprague Dawley rats in an Extended One-Generation Reproductive Toxicity Study (OECD Test Guideline 443). The dosed diet began 14 days before mating and was continued at the same concentration level for the entire study for all parental animals (P0) and offspring (F1). At weaning, offspring were allocated into one of 5 cohorts for different endpoints. P0 and F1 animals had blue urine, blue or black feces, and blue discolorations in gastrointestinal organs, mesenteric lymph nodes, and kidneys. This treatment-related finding was not considered adverse as there were no histopathologic correlates. There was a dose-related increase in sperm concentration in P0 and F1 males. There were dose-related increases in heart weights of F1 postnatal day (PND) 21 males, male and female thyroid weights, and female TSH levels of PND 91 F1 offspring, with no histopathological correlate. There were no consistent treatment-related adverse effects on any other parameters evaluated for general toxicity, reproductive toxicity, developmental neurotoxicity, or developmental immunotoxicity. The highest dietary concentration (5.0%) of gardenia blue powder was the no observed adverse effect level (NOAEL) for male and female rats at all life stages evaluated.

Unraveling a Combined Inactivation Mechanism of Cytochrome P450s by Genipin, the Major Reactive Aglycone Derived from Gardeniae Fructus

Genipin (GP) is the reactive aglycone of geniposide, the main component of traditional Chinese medicine Gardeniae Fructus (GF). The covalent binding of GP to cellular proteins is suspected to be responsible for GF-induced hepatotoxicity and inhibits drug-metabolizing enzyme activity, although the mechanisms remain to be clarified. In this study, the mechanisms of GP-induced human hepatic P450 inactivation were systemically investigated. Results showed that GP inhibited all tested P450 isoforms via distinct mechanisms. CYP2C19 was directly and irreversibly inactivated without time dependency. CYP1A2, CYP2C9, CYP2D6, and CYP3A4 T (testosterone as substrate) showed time-dependent and mixed-type inactivation, while CYP2B6, CYP2C8, and CYP3A4 M (midazolam as substrate) showed time-dependent and irreversible inactivation. For CYP3A4 inactivation, the kinact/KI values in the presence or absence of NADPH were 0.26 or 0.16 min-1 mM-1 for the M site and 0.62 or 0.27 min-1 mM-1 for the T site. Ketoconazole and glutathione (GSH) both attenuated CYP3A4 inactivation, suggesting an active site occupation- and reactive metabolite-mediated inactivation mechanism. Moreover, the in vitro and in vivo formation of a P450-dependent GP-S-GSH conjugate indicated the involvement of metabolic activation and thiol residues binding in GP-induced enzyme inactivation. Lastly, molecular docking analysis simulated potential binding sites and modes of GP association with CYP2C19 and CYP3A4. We propose that direct covalent binding and metabolic activation mediate GP-induced P450 inactivation and alert readers to potential risk factors for GP-related clinical drug-drug interactions.

Soy Protein Isolate/Genipin-Based Nanoparticles for the Stabilization of Pickering Emulsion to Design Self-Healing Guar Gum-Based Hydrogels

Nowadays, stretchable self-healing hydrogels designed by biomass-based materials have gathered remarkable attention in numerous frontier fields such as wound healing, health monitoring issues, and electronic skin. In this study, soy protein isolate (SPI), a common plant protein, was cross-linked to nanoparticles (SPI NPs) by Genipin, (Gen) which was attracted from the native Geniposide. Oil-in-water (O/W) Pickering emulsion was formed by SPI NPs wrapping the linseed oil, and further implanted into poly(acrylic acid)/guar gum (PAA/GG)-based self-healing hydrogels by multiple reversible weak interactions. With the addition of Pickering emulsion, the hydrogels have achieved a remarkable self-healing ability (self-healing efficiency could reach 91.6% within 10 h) and mechanical properties (tensile strength of 0.89 MPa and strain of 853.2%). Therefore, these hydrogels with good reliable durability have outstanding application prospects in sustainable materials.

Chronic toxicity and carcinogenicity study of dietary gardenia blue in Sprague Dawley rats

In this combined chronic toxicity/carcinogenicity study of gardenia blue as a natural food color additive, Sprague Dawley rats were administered 0.5%, 2.5%, or 5.0% gardenia blue via the feed or carrier diet (0.0% gardenia blue) for 12 (chronic toxicity cohort) or 24 (carcinogenicity cohort) months. No abnormal clinical, ophthalmological, neurotoxicity or clinical pathology changes were attributed to treatment, and there was no increase in mortality due to gardenia blue exposure. The only treatment-related change was grossly observed blue discoloration of the stomach, intestines, and mesenteric lymph nodes as well as reversible dark discoloration of the kidneys all without associated histopathology. The no-observed-adverse-effect level (NOAEL) for gardenia blue exposure via the diet for one or two years was determined to be 5.0% (2175.3 mg/kg body weight/day in male rats and 3075.4 mg/kg body weight/day in female rats).

High efficiency biosynthesis of gardenia blue and red pigment by lactic acid bacteria: A great potential for natural color pigments

Current production methods of the food colorants, gardenia blue (GB) and red (GR) pigments have low efficiency. One potential approach involves using lactic acid bacteria (LAB), which produce a high level of β-glucosidase, produce the GB and GR using non-toxic and harmless process. The isolated strain Lactobacillus plantarum S3 and the reference strain Lb. plantarum KCTC3104 showed high β-glucosidase activity levels of 1.01 and 1.44 unit/mL, respectively. The 12-h bioconversion yield of geniposide to genipin using two strains were 93.4% and 100%, respectively, which are high conversion percentage. For GB, the maximal production yield obtained using Lb. plantarum S3 and Lb. plantarum KCTC3104 under optimal conditions were 2.17 and 2.18 mg/mL, respectively. For GR, glutamic acid (Glu) with Lb. plantarum S3 is the best combination. To the best of our knowledge, this is the first report of an effective alternative method for the production of natural food colorants using LAB.

Sustainable fashion: eco-friendly dyeing of wool fiber with novel mixtures of biodegradable natural dyes

Natural materials, especially natural colorants, have achieved global prominence and might be regarded as an environmentally beneficial alternative to hazardous synthetic dyes. The color limitation of natural dyes hinders their application in textiles. The present work aims to prepare more color shades of wool yarns via dyeing with ternary natural dye mixtures without adding mordants. In this study, a sustainable dyeing approach for wool yarn was evaluated with three natural dyes, madder red (MR), gardenia blue (GB), and gardenia yellow (GY), by following an industrial dyeing procedure in the absence of a mordant. In the beginning, a preliminary assessment of dye stabilities was carried out, and it was found that the three natural dyes were sensitive to temperature and acid (degradation tendency). Then, the dyeing behavior was systematically evaluated, including a single natural dye, a binary natural dye mixture, and a ternary natural dye mixture. The results of wool yarn dyeing with a single natural dye show that the dye exhaustion percentage (E%) of MR, GY, and GB was in the ranges of 78.7-94.1%, 13.4-44.1%, and 54.8-68.5%, respectively. The dyeing results of wool yarns dyed with binary and ternary natural dye mixtures (a color triangle framework of dyed wool yarn) were characterized by colorimetric values (L*, a*, b*, C*, h, and K/S), and are presented to enlighten various colorful shades. Finally, color uniformity and colorfastness tests confirmed the vital contribution of natural dyes toward wool yarn coloration. Particularly, colorfastness to washing confirmed the stability of natural dyes with reference to the lower amount of dyes released into the effluent, which is beneficial for the environment. Overall, this study provides a good background for enhancing the industrialization trend of natural dyes by modulating their dyeing scheme.

Isolation of the Thermostable β-Glucosidase-Secreting Strain Bacillus altitudinis JYY-02 and Its Application in the Production of Gardenia Blue

Gardenia blue (GB) is a natural blue pigment widely used in textiles and the pharmaceutical industry. The geniposide in gardenia fruits can be hydrolyzed by β-glucosidase to form genipin, which reacts with amino acids to produce GB. In this study, a bacterial strain which secreted thermostable β-glucosidase (EC 3.2.1.21) was isolated from soil and identified as Bacillus altitudinis JYY-02. This strain could potentially be used for GB production from geniposide by fermentation. Optimal fermentation results were achieved at pH 6.5 or 8.0 at 45°C for 45 h with additional sucrose. To obtain a large amount of β-glucosidase, the whole genome of B. altitudinis JYY-02 was sequenced and annotated; it is 3,727,518 bp long and contains 3,832 genes. The gene encoding β-glucosidase (bgl) in B. altitudinis JYY-02 was screened from the genome and overexpressed in Escherichia coli BL21(DE3). The recombinant β-glucosidase was purified by affinity chromatography on a Ni Sepharose 6 fast flow (FF) column. The optimal temperature, pH, and Km values for the recombinant β-glucosidase were 60°C, pH 5.6, and 0.331 mM, respectively, when p-nitrophenyl-β-d-glucopyranoside (pNPG) was used as the substrate. The recombinant β-glucosidase catalyzed the deglycosylation reaction of geniposide, which was then used to produce GB. IMPORTANCE β-Glucosidases are enzymes capable of hydrolyzing β-glucosidic linkages present in saccharides and glycosides and have many agricultural and industrial applications. Although they are found in all domains of living organisms, commercial β-glucosidases are still expensive, limiting their application in industry. In the present study, a thermostable β-glucosidase-producing strain was obtained for GB production by fermentation, engineered bacteria were constructed for preparing recombinant β-glucosidase, and a one-step method to purify the recombinant enzyme was established. A large amount of purified β-glucosidase was easily obtained from the engineered bacteria for industrial applications such as GB production.