Simultaneous suppression of lignin, tricin and wall-bound phenolic biosynthesis via the expression of monolignol 4-O-methyltransferases in rice.

Grass lignocelluloses feature complex compositions and structures. In addition to the presence of conventional lignin units from monolignols, acylated monolignols and flavonoid tricin also incorporate into lignin polymer; moreover, hydroxycinnamates, particularly ferulate, cross-link arabinoxylan chains with each other and/or with lignin polymers. These structural complexities make grass lignocellulosics difficult to optimize for effective agro-industrial applications. In the present study, we assess the applications of two engineered monolignol 4-O-methyltransferases (MOMTs) in modifying rice lignocellulosic properties. Two MOMTs confer regiospecific para-methylation of monolignols but with different catalytic preferences. The expression of MOMTs in rice resulted in differential but drastic suppression of lignin deposition, showing more than 50% decrease in guaiacyl lignin and up to an 90% reduction in syringyl lignin in transgenic lines. Moreover, the levels of arabinoxylan-bound ferulate were reduced by up to 50%, and the levels of tricin in lignin fraction were also substantially reduced. Concomitantly, up to 11 µmol/g of the methanol-extractable 4-O-methylated ferulic acid and 5-7 µmol/g 4-O-methylated sinapic acid were accumulated in MOMT transgenic lines. Both MOMTs in vitro displayed discernible substrate promiscuity towards a range of phenolics in addition to the dominant substrate monolignols, which partially explains their broad effects on grass phenolic biosynthesis. The cell wall structural and compositional changes resulted in up to 30% increase in saccharification yield of the de-starched rice straw biomass after diluted acid-pretreatment. These results demonstrate an effective strategy to tailor complex grass cell walls to generate improved cellulosic feedstocks for the fermentable sugar-based production of biofuel and bio-chemicals.

A multi-omics approach to lignocellulolytic enzyme discovery reveals a new ligninase activity from Parascedosporium putredinis NO1.

Lignocellulose, the structural component of plant cells, is a major agricultural byproduct and the most abundant terrestrial source of biopolymers on Earth. The complex and insoluble nature of lignocellulose limits its conversion into value-added commodities, and currently, efficient transformation requires expensive pretreatments and high loadings of enzymes. Here, we report on a fungus from the Parascedosporium genus, isolated from a wheat-straw composting community, that secretes a large and diverse array of carbohydrate-active enzymes (CAZymes) when grown on lignocellulosic substrates. We describe an oxidase activity that cleaves the major ß-ether units in lignin, thereby releasing the flavonoid tricin from monocot lignin and enhancing the digestion of lignocellulose by polysaccharidase mixtures. We show that the enzyme, which holds potential for the biorefining industry, is widely distributed among lignocellulose-degrading fungi from the Sordariomycetes phylum.

Seasonal and Circadian Variation of Non-Volatile Metabolites in Lippia alba Leaves.

The present study describes the seasonal and circadian variations of the major compounds from Lippia alba leaves. SPSS was used to identify, quantify, and associate the variations in the secondary metabolites of this species through HPLC/DAD analysis of the leaves hydroethanolic extracts of six selected L. alba specimens. For the circadian study, the samples were collected at four different daily hours in each year's season. For the seasonal study, the samples were collected monthly from the same individuals for two consecutive years (2018 and 2019). These samples were analyzed and quantified using a validated HPLC method for flavonoids, iridoids, and phenyl ethanoid glycoside. Mussaenoside, acteoside, and tricin-7-O-diglucuronide showed a moderate positive correlation between their biosynthesis and the precipitation index, while epi-loganin had a moderate negative correlation. Acteoside showed a moderate positive correlation between the minimum registered temperature and its production. Compared with previous studies, a drastic reduction (about 95 %) in the production of tricin-7-O-diglucuronide compared with previous study and this difference could be attributed to the plant's aging. Thus, the data demonstrated that lower temperatures and high rainfall could favor the production of the major L. alba active compounds (acteoside and tricin-7-O-diglucuronide) and that older plants harm their production.

Tricin promoted ATG-7 dependent autophagic degradation of α-synuclein and dopamine release for improving cognitive and motor deficits in Parkinson's disease.

Tricin, a natural nontoxic flavonoid distributed in grasses and euphorbia plants, has been reported to scavenge free radicals, possess anti-inflammatory and antioxidative effects. However, its autophagic effect on Parkinson's disease (PD) has not been elucidated. By adopting cellular and C. elegans models of PD, the autophagic effect of tricin was identified based on the level of autophagy markers (LC3-II and p62). Besides, the pharmacological effects on neurotransmitters (dopamine), inflammatory cytokines (IFN γ, TNFα, MCP-1, IL-10, IL-6 and IL-17A), histology (hematoxylin & eosin and Nissl staining) and behavioural pathology (open-field test, hindlimb clasping, Y-maze, Morris water-maze and nest building test) were also confirmed in the A53T-α-synuclein transgenic PD mouse model. Further experiments demonstrated that tricin induced autophagic flux and lowered the level of α-synuclein through AMPK-p70s6K- and ATG7-dependent mechanism. Compared to the existing clinical PD drugs, tricin mitigated pathogenesis and symptoms of PD with no observable side effects. In summary, tricin is proposed as a potential adjuvant remedy or nutraceutical for the prevention and treatment of PD.

Tricin attenuates the progression of LPS-induced severe pneumonia in bronchial epithelial cells by regulating AKT and MAPK signaling pathways.

BACKGROUND: Pneumonia is a continuous and widespread disease with higher incidence, the effects of it on human life can be fearful. Tricin has been demonstrated to take part in the progression and development of diseases. However, the function of Tricin and its related regulatory pathways remain unclear. This study was planned to investigate the effects of Tricin on severe pneumonia. METHODS: The cell viability was detected through CCK-8 assay. The TNF-α, IL-1ß and IL-6 levels were assessed through ELISA and RT-qPCR. The levels of MDA, SOD and GSH were tested through corresponding commercial kits. The protein expressions were examined through western blot. RESULTS: In our study, the lipopolysaccharide (LPS) was firstly used to stimulate cell model for severe pneumonia. We discovered that Tricin had no toxic effects on BEAS-2B cells and the decreased cell viability induced by LPS was relieved by a dose-dependent Tricin treatment. Additionally, through ELISA and RT-qPCR, it was uncovered that Tricin reduced the LPS-induced inflammation through regulating TNF-α, IL-1ß and IL-6. Furthermore, Tricin relieved LPS-induced oxidative stress through reducing MDA level and enhancing SOD and GSH levels. Finally, it was demonstrated that Tricin retarded LPS-activated AKT and MAPK pathways. CONCLUSION: Our findings revealed that Tricin attenuated the progression of LPS induced severe pneumonia through modulating AKT and MAPK signaling pathways. This discovery might afford one novel sight for the treatment of severe pneumonia.

Zizania latifolia and Its Major Compound Tricin Regulate Immune Responses in OVA-Treated Mice.

Tricin, a flavone belonging to the Gramineae family, has been confirmed to be the primary compound in a Zizania latifolia extract (ZLE) that prevents allergies. Various allergic reactions occur because of the unbalanced differentiation of T help cells (Th) and the consequent overproduction of IgE. Therefore, the regulation of Th1 and Th2 responses by T helper cell differentiation is essential for suppressing allergic responses. This study confirmed the immunomodulatory effects of ZLE and the major compound tricin in an OVA-sensitized mouse model. The IgE and OVA-specific production of tricin and ZLE in plasma were investigated in OVA-sensitized mice. The effects of tricin and ZLE on the amount of Th1 and Th2 cytokines and transcription factors released in splenocytes were investigated in OVA-sensitized mice. The skin roughness and the number of mast cells were confirmed by staining the skin surface with H&E and toluidine blue. Tricin and ZLE reduced the plasma IgE and OVA-specific-IgE levels significantly compared to the OVA group. On the other hand, tricin and ZLE promoted the release of the Th1 cytokines IL-12 and IFN-γ and inhibited the release of Th2 cytokines (IL-4, -10, -13, and -5) in OVA-sensitized mice. Tricin and ZLE induced T-bet and NFATc2 expression, and-down regulated GATA-3 levels. The skin roughness and the number of mast cells decreased in the OVA-immunized mice. Overall, the data indicate that tricin and ZLE may prevent allergy-related diseases through immunomodulation.

Genetic Architecture of Maize Rind Strength Revealed by the Analysis of Divergently Selected Populations.

The strength of the stalk rind, measured as rind penetrometer resistance (RPR), is an important contributor to stalk lodging resistance. To enhance the genetic architecture of RPR, we combined selection mapping on populations developed by 15 cycles of divergent selection for high and low RPR with time-course transcriptomic and metabolic analyses of the stalks. Divergent selection significantly altered allele frequencies of 3,656 and 3,412 single- nucleotide polymorphisms (SNPs) in the high and low RPR populations, respectively. Surprisingly, only 110 (1.56%) SNPs under selection were common in both populations, while the majority (98.4%) were unique to each population. This result indicated that high and low RPR phenotypes are produced by biologically distinct mechanisms. Remarkably, regions harboring lignin and polysaccharide genes were preferentially selected in high and low RPR populations, respectively. The preferential selection was manifested as higher lignification and increased saccharification of the high and low RPR stalks, respectively. The evolution of distinct gene classes according to the direction of selection was unexpected in the context of parallel evolution and demonstrated that selection for a trait, albeit in different directions, does not necessarily act on the same genes. Tricin, a grass-specific monolignol that initiates the incorporation of lignin in the cell walls, emerged as a key determinant of RPR. Integration of selection mapping and transcriptomic analyses with published genetic studies of RPR identified several candidate genes including ZmMYB31, ZmNAC25, ZmMADS1, ZmEXPA2, ZmIAA41 and hk5. These findings provide a foundation for an enhanced understanding of RPR and the improvement of stalk lodging resistance.

Metabolomics and integrated network pharmacology analysis reveal Tricin as the active anti-cancer component of Weijing decoction by suppression of PRKCA and sphingolipid signaling.

Currently, conventional methods of treating non-small cell lung cancer (NSCLC) have many disadvantages. An alternative effective therapy with minimal adverse reactions is urgently needed. Weijing decoction (WJD), which is a classic ancient Chinese herbal prescription, has been used successfully to treat pulmonary system diseases containing lung cancer in the clinic. However, the key active component and target of Weijing decoction are still unexplored. Therefore, for the first time, our study aims to investigate the pharmacological treatment mechanism of Weijing decoction in treating NSCLC via an integrated model of network pharmacology, metabolomics and biological methods. Network pharmacology results conjectured that Tricin is a main bioactive component in this formula which targets PRKCA to suppress cancer cell growth. Metabolomics analysis demonstrated that sphingosine-1-phosphate, which is regulated by sphingosine kinase 1 and sphingosine kinase 2, is a differential metabolite in plasma between the WJD-treated group and the control group, participating in the sphingolipid signaling. In vitro experiments demonstrated that Tricin had vital effects on the proliferation, pro-apoptosis, migration and colony formation of Lewis lung carcinoma cells. Through a series of validation assays, Tricin inhibited the tumor growth mainly by suppressing PRKCA/SPHK/S1P signaling and antiapoptotic signaling. On the other hand, Weijing formula could inhibit the tumor growth and prolong the survival time. A high dosage of Tricin was much more potent in animal experiments. In conclusion, we confirmed that Weijing formula and its primary active compound Tricin are promising alternative treatments for NSCLC patients.

Barnyard grass [Echinochloa crus-galli (L.) Beauv] leaves extract against tomato pests.

BACKGROUND: Tomato is one of the widely cultivated crops worldwide that is affected by several pests, such as fungi (Fusarium oxysoporum, Alternaria solani), bacteria (Pectobacterium carotovorum) and weeds (Cyperus iria L., Amaranthus spinosus). A growing interest has emerged for developing plant-derived pesticidal compounds to counteract these pests. One attractive alternative is to use barnyard grass (Echinochloa crus-galli), known to be widely resistant to synthetic herbicides, as a potential biopesticide compound source. RESULTS: Phytochemical screening of the crude extract showed that phenolic compounds were the most abundant component present in barnyard grass. The crude extract was evaluated for antifungal, antibacterial and herbicidal activities. Bioassays showed inhibition against F. oxysporum (10.73 ± 1.30%) and A. solani (20.47 ± 3.51%), the causative agent of Fusarium rot and early blight disease in tomato, respectively. Antibacterial activity against P. carotovorum gave a mean zone of inhibition (paper disc diffusion assay) of 17.00 ± 1.00 mm and an IC50 (dose-response assay) of 2.26 mg mL-1 was observed. Dose-responsive herbicidal activity on the lettuce seed germination bioassay produced an IC50 of 459.30 ppm. Selectivity studies showed inhibition towards C. iria and A. spinosus with no effect on tomato. Lastly, bioassay-guided fractionation coupled with untargeted metabolomics studies using ultra-performance liquid chromatography with diode array detection-tandem mass spectrometry mass analyses revealed loliolide and tricin as the putative metabolites present in barnyard grass. CONCLUSION: To date, this is the first reported study on using barnyard grass as a potential alternative biopesticide against tomato pests such as fungi, bacteria and weeds. © 2021 Society of Chemical Industry.

OsMYB108 loss-of-function enriches p-coumaroylated and tricin lignin units in rice cell walls.

Breeding approaches to enrich lignins in biomass could be beneficial to improving the biorefinery process because lignins increase biomass heating value and represent a potent source of valuable aromatic chemicals. However, despite the fact that grasses are promising lignocellulose feedstocks, limited information is yet available for molecular-breeding approaches to upregulate lignin biosynthesis in grass species. In this study, we generated lignin-enriched transgenic rice (Oryza sativa), a model grass species, via targeted mutagenesis of the transcriptional repressor OsMYB108 using CRISPR/Cas9-mediated genome editing. The OsMYB108-knockout rice mutants displayed increased expressions of lignin biosynthetic genes and enhanced lignin deposition in culm cell walls. Chemical and two-dimensional nuclear magnetic resonance (NMR) analyses revealed that the mutant cell walls were preferentially enriched in γ-p-coumaroylated and tricin lignin units, both of which are typical and unique components in grass lignins. NMR analysis also showed that the relative abundances of major lignin linkage types were altered in the OsMYB108 mutants.

Convergent recruitment of 5'-hydroxylase activities by CYP75B flavonoid B-ring hydroxylases for tricin biosynthesis in Medicago legumes.

Tricin (3',5'-dimethoxylated flavone) is a predominant flavonoid amongst monocots but occurs only in isolated and unrelated dicot lineages. Although tricin biosynthesis has been intensively studied in monocots, it has remained largely elusive in tricin-accumulating dicots. We investigated a subgroup of cytochrome P450 (CYP) 75B subfamily flavonoid B-ring hydroxylases (FBHs) from two tricin-accumulating legumes, Medicago truncatula and alfalfa (Medicago sativa), by phylogenetic, molecular, biochemical and mutant analyses. Five Medicago cytochrome P450 CYP75B FBHs are phylogenetically distant from other legume CYP75B members. Among them, MtFBH-4, MsFBH-4 and MsFBH-10 were expressed in tricin-accumulating vegetative tissues. In vitro and in planta analyses demonstrated that these proteins catalyze 3'- and 5'-hydroxylations critical to tricin biosynthesis. A key amino acid polymorphism, T492G, at their substrate recognition site 6 domain is required for the novel 5'-hydroxylation activities. Medicago truncatula mtfbh-4 mutants were tricin-deficient, indicating that MtFBH-4 is indispensable for tricin biosynthesis. Our results revealed that these Medicago legumes had acquired the tricin pathway through molecular evolution of CYP75B FBHs subsequent to speciation from other nontricin-accumulating legumes. Moreover, their evolution is independent of that of grass-specific CYP75B apigenin 3'-hydroxylases/chrysoeriol 5'-hydroxylases dedicated to tricin production and Asteraceae CYP75B flavonoid 3',5'-hydroxylases catalyzing the production of delphinidin-based pigments.

A Natural Flavone Tricin from Grains Can Alleviate Tumor Growth and Lung Metastasis in Colorectal Tumor Mice.

Tricin, a flavone isolated from rice bran, has been shown to be chemopreventive in a colorectal cancer (CRC) mouse model. This study aimed to illustrate the inhibitory activities of tricin in colon cancer cells and in a metastatic CRC mouse model. BALB/c mice injected with mouse Colon26-Luc cells into the rectum wall were treated with tricin (37.5 mg/kg) daily for 18 days. Orthotopic colon tumor growth and metastasis to lungs were assessed by in vivo bioluminescence imaging. Results showed that tricin suppressed Colon-Luc cells motility and downregulated phosphorylated Akt, Erk1/2 and NF-κB expressions of human colon cancer HT-29 cells. While tricin treatment suppressed tumor growth and lung metastasis as well as altered the populations of myeloid-derived suppressor cells and regulatory T cells in spleens. In summary, the tumor microenvironment modulatory and anti-metastatic effects of tricin in colon cancer mouse model were shown for the first time, suggesting the potential development of tricin-containing food supplements for CRC patients.

Tricin Isolated from Enzyme-Treated Zizania latifolia Extract Inhibits IgE-Mediated Allergic Reactions in RBL-2H3 Cells by Targeting the Lyn/Syk Pathway.

Tricin, a flavone present in rice bran, is confirmed as the major efficacious compound present in the enzyme-treated Zizania latifolia extract (ETZL), which protects against UVB-induced skin-aging. However, the suppressive mechanism of tricin on allergic responses remains unknown. The present study, therefore, aimed to determine the mechanisms of tricin and ETZL on mast cell degranulation in IgE-activated rat basophilic leukemia cell line (RBL-2H3) cells. We investigated the regulatory effects of tricin and ETZL on degranulation, production of cytokines and lipid mediators, and signaling proteins involved in the IgE-bound high-affinity IgE receptor activation, mitogen-activated protein kinase, arachidonic acid and Syk. The production of ß-hexosaminidase, tumor necrosis factor-α, interleukin-4, leukotrienes (LT) B4, LTC4 and prostaglandin E2 in IgE-stimulated RBL-2H3 cells were significantly inhibited by exposure to tricin or ETZL. Moreover, tricin and ETZL inhibit the phosphorylation of cytosolic phospholipase A2, 5-lipoxygenase and cyclooxygenase-2. Furthermore, the phosphorylation of Akt, ERK, p38, JNK, protein kinase Cδ and phospholipase Cγ1 were effectively suppressed by both samples. Exposure to tricin or ETZL also significantly decreases the phosphorylation of Lyn and Syk, but has minimal effect on Fyn. Taken together, our data indicate that tricin and ETZL are potential anti-allergic materials that could be applied for the prevention of allergy-related diseases.

Recruitment of specific flavonoid B-ring hydroxylases for two independent biosynthesis pathways of flavone-derived metabolites in grasses.

In rice (Oryza sativa), OsF2H and OsFNSII direct flavanones to independent pathways that form soluble flavone C-glycosides and tricin-type metabolites (both soluble and lignin-bound), respectively. Production of soluble tricin metabolites requires CYP75B4 as a chrysoeriol 5'-hydroxylase. Meanwhile, the close homologue CYP75B3 is a canonical flavonoid 3'-hydroxylase (F3'H). However, their precise roles in the biosynthesis of soluble flavone C-glycosides and tricin-lignins in cell walls remain unknown. We examined CYP75B3 and CYP75B4 expression in vegetative tissues, analyzed extractable flavonoid profiles, cell wall structure and digestibility of their mutants, and investigated catalytic activities of CYP75B4 orthologues in grasses. CYP75B3 and CYP75B4 showed co-expression patterns with OsF2H and OsFNSII, respectively. CYP75B3 is the sole F3'H in flavone C-glycosides biosynthesis, whereas CYP75B4 alone provides sufficient 3',5'-hydroxylation for tricin-lignin deposition. CYP75B4 mutation results in production of apigenin-incorporated lignin and enhancement of cell wall digestibility. Moreover, tricin pathway-specific 3',5'-hydroxylation activities are conserved in sorghum CYP75B97 and switchgrass CYP75B11. CYP75B3 and CYP75B4 represent two different pathway-specific enzymes recruited together with OsF2H and OsFNSII, respectively. Interestingly, the OsF2H-CYP75B3 and OsFNSII-CYP75B4 pairs appear to be conserved in grasses. Finally, manipulation of tricin biosynthesis through CYP75B4 orthologues can be a promising strategy to improve digestibility of grass biomass for biofuel and biomaterial production.

Protection against UVB-induced damages in human dermal fibroblasts: efficacy of tricin isolated from enzyme-treated Zizania latifolia extract.

This study was undertaken to determine the effects of enzyme-treated Zizania latifolia (ETZL) and of its major compound tricin on skin photo-aging and to investigate the mechanisms involved. It was found ETZL and tricin suppressed matrix metalloproteinase (MMP) production and increased type I-procollagen production in UVB-irradiated human dermal fibroblasts (HDFs). Furthermore, ETZL and tricin significantly up-regulated the expressions of the antioxidant enzymes HO-1 and SOD1, reduced UVB-induced reactive oxygen species (ROS) generation and mitogen-activated protein kinase (MAPK) induction by ROS and thereby attenuated activator protein-1 (AP-1) expression. In addition, ETZL and tricin both reduced the phosphorylations of IκBα and IKKα/ß and κB blocked the nuclear translocation of nuclear factor-κB (NF-κB) p65. These results show that ETZL have skin protective effects against UVB and suggest tricin as major efficacious material in ETZL protecting skin photoaging.

Puccinellia maritima, Spartina maritime, and Spartina patens Halophytic Grasses: Characterization of Polyphenolic and Chlorophyll Profiles and Evaluation of Their Biological Activities.

Halophytic grasses have been recently targeted as possible sources of nutraceutical and medicinal compounds. Nonetheless, few studies have been conducted on the phytochemistry and biological activities of metabolites produced by these plants. Among these, Spartina maritima (Curtis) Fernald, Spartina patens (Aiton.) Muhl., and Puccinellia maritima (Hudson) Parl. are three halophytic grasses whose chemical composition and bioactivities are unknown. The present work broadens the knowledge on the polyphenolic and chlorophyll composition of these species identifying for the first time hydroxycinnamic acids and their derivatives, flavones, flavonols, lignans, as well as chlorophylls and xantophylls. The extracts were particularly rich in caffeic and ferulic acids as well as in trihydroxymethoxyflavone, apigenin and tricin derivatives. Interestingly, several of the identified compounds are relevant from a medicinal and nutraceutical point of view putting in evidence the potential of these species. Thus, the antioxidant, anti-acetylcholinesterase, antibacterial, and antifungal activities of the polyphenolic extracts were assessed as well as the photophysical properties of the chlorophyll-rich extracts. The results, herein presented for the first time, reinforce the nutritional and the medicinal potential of these halophytic grasses.

Partial purification, characterization and mode of action of bacteriocins produced by three strains of Pediococcus sp.

The main objective of the study is to assess a comparative antibacterial potential of three new bacteriocins produced by Pediococcus sp. through partial characterization and mode of action against some food spoilage bacteria. The bacteriocins from three different Pediococcus sp. viz. Pediococcus sp. LAB 33 (HQ185406), Pediococcus sp. LAB 41 (HQ185407), and Pediococcus sp. LAB 51 (HQ184064) were partially purified by adsorption-desorption method and tested for autoclave heat, pH, detergent and enzymes stability. A comparative analysis by Tricin-SDS PAGE with MALDI-TOF MS was done to estimate their molecular weight. The mode of action studies were done by cell viability and lactate dehydrogenase assay against two food associated pathogens, viz. Listeria monocytogenes and Pseudomonas aeruginosa using standard protocols. The bacteriocins produced by the strains were resistant to autoclave heat, detergent, wide range of pH and were active against different food borne pathogens at a minimum dose of ~ 100 AU/ml. The mode of action studies showed bactericidal action with lysis of the targeted cells. Therefore, the selective low dose efficacy, heat and detergent stability of the bacteriocins produced by the three strains could be considered as potent bacteriocins for use as food preservatives.

In Vitro Enzymatic Depolymerization of Lignin with Release of Syringyl, Guaiacyl, and Tricin Units.

New environmentally sound technologies are needed to derive valuable compounds from renewable resources. Lignin, an abundant polymer in terrestrial plants comprised predominantly of guaiacyl and syringyl monoaromatic phenylpropanoid units, is a potential natural source of aromatic compounds. In addition, the plant secondary metabolite tricin is a recently discovered and moderately abundant flavonoid in grasses. The most prevalent interunit linkage between guaiacyl, syringyl, and tricin units is the ß-ether linkage. Previous studies have shown that bacterial ß-etherase pathway enzymes catalyze glutathione-dependent cleavage of ß-ether bonds in dimeric ß-ether lignin model compounds. To date, however, it remains unclear whether the known ß-etherase enzymes are active on lignin polymers. Here we report on enzymes that catalyze ß-ether cleavage from bona fide lignin, under conditions that recycle the cosubstrates NAD+ and glutathione. Guaiacyl, syringyl, and tricin derivatives were identified as reaction products when different model compounds or lignin fractions were used as substrates. These results demonstrate an in vitro enzymatic system that can recycle cosubstrates while releasing aromatic monomers from model compounds as well as natural and engineered lignin oligomers. These findings can improve the ability to produce valuable aromatic compounds from a renewable resource like lignin.IMPORTANCE Many bacteria are predicted to contain enzymes that could convert renewable carbon sources into substitutes for compounds that are derived from petroleum. The ß-etherase pathway present in sphingomonad bacteria could cleave the abundant ß-O-4-aryl ether bonds in plant lignin, releasing a biobased source of aromatic compounds for the chemical industry. However, the activity of these enzymes on the complex aromatic oligomers found in plant lignin is unknown. Here we demonstrate biodegradation of lignin polymers using a minimal set of ß-etherase pathway enzymes, the ability to recycle needed cofactors (glutathione and NAD+) in vitro, and the release of guaiacyl, syringyl, and tricin as depolymerized products from lignin. These observations provide critical evidence for the use and future optimization of these bacterial ß-etherase pathway enzymes for industrial-level biotechnological applications designed to derive high-value monomeric aromatic compounds from lignin.

Tricin inhibits the CCL5 induction required for efficient growth of human cytomegalovirus.

Treatment of human embryonic lung fibroblast (HEL) cells with tricin (4', 5, 7-trihydroxy-3', 5'-dimethoxyflavone) following infection with human cytomegalovirus (HCMV) reportedly significantly suppresses HCMV replication. In the present work, the mechanisms for the anti-HCMV effects of tricin in HEL cells were examined. It was found that exposure of HEL cells to tricin inhibited HCMV replication, with concomitant decreases in amounts of transcripts of the CC chemokine RANTES (CCL5)-encoding gene and in expression of the CCL5 protein. It was also found that transcripts of HCMV immediate early 1 (IE1), and HCMV UL54 (encoding DNA polymerase) and replication of HCMV was significantly lower in CCL5 gene-knockdown cells. These results suggest that the anti-HCMV activity of tricin differs from that of ganciclovir and that CCL5 is one of the chemokines involved in HCMV replication. In addition, it is possible that chemokine CCL5 is one of the targets of tricin.

Protection against UVB-Induced Wrinkle Formation in SKH-1 Hairless Mice: Efficacy of Tricin Isolated from Enzyme-Treated Zizania latifolia Extract.

Tricin, a flavone found mainly in rice bran and sugarcane, has various beneficial effects. It has proven to be a clinically safe and selective potent inhibitor of different cancer cell lines. In this study, we evaluated the efficacy of enzyme-treated Zizania latifolia (ETZL) and its major active compound tricin on skin photoaging in SKH-1 hairless mice. Tricin (0.3 mg/kg) and ETZL (50, 150, and 300 mg/kg) were orally administrated to mice for 14 weeks; no cytotoxicity was observed during the entire experimental period. After UVB exposure, we observed significant increases in keratinization, coarse wrinkles, loss of moisture, thickened epidermis, and collagen fiber degradation in the dorsal skin. These features of photoaging were significantly suppressed after oral administration of tricin or ETZL. In addition, the protein expression of collagen effectively increased in ETZL (150 and 300 mg/kg)-treated mice, while the increased metalloproteinase (MMP)-1 and MMP-3 expressions were reduced after exposure to tricin or ETZL, although the effects were not dose-dependent. These data indicate that ETZL may be effective for attenuation of UVB-induced skin damage and photoaging in hairless mice, possibly by inhibiting MMPs expression.