Quinic acid regulated TMA/TMAO-related lipid metabolism and vascular endothelial function through gut microbiota to inhibit atherosclerotic

BACKGROUND

Quinic acid (QA) and its derivatives have good lipid-lowering and hepatoprotective functions, but their role in atherosclerosis remains unknown. This study attempted to investigate the mechanism of QA on atherogenesis in Apoe-/- mice induced by HFD.

METHODS

HE staining and oil red O staining were used to observe the pathology. The PCSK9, Mac-3 and SM22a expressions were detected by IHC. Cholesterol, HMGB1, TIMP-1 and CXCL13 levels were measured by biochemical and ELISA. Lipid metabolism and the HMGB1-SREBP2-SR-BI pathway were detected by PCR and WB. 16 S and metabolomics were used to detect gut microbiota and serum metabolites.

RESULTS

QA or low-frequency ABX inhibited weight gain and aortic tissue atherogenesis in HFD-induced Apoe-/- mice. QA inhibited the increase of cholesterol, TMA, TMAO, CXCL13, TIMP-1 and HMGB1 levels in peripheral blood of Apoe-/- mice induced by HFD. Meanwhile, QA or low-frequency ABX treatment inhibited the expression of CAV-1, ABCA1, Mac-3 and SM22α, and promoted the expression of SREBP-1 and LXR in the vascular tissues of HFD-induced Apoe-/- mice. QA reduced Streptococcus_danieliae abundance, and promoted Lactobacillus_intestinalis and Ileibacterium_valens abundance in HFD-induced Apoe-/- mice. QA altered serum galactose metabolism, promoted SREBP-2 and LDLR, inhibited IDOL, FMO3 and PCSK9 expression in liver of HFD-induced Apoe-/- mice. The combined treatment of QA and low-frequency ABX regulated microbe-related Glycoursodeoxycholic acid and GLYCOCHENODEOXYCHOLATE metabolism in HFD-induced Apoe-/- mice. QA inhibited TMAO or LDL-induced HCAECs damage and HMGB1/SREBP2 axis dysfunction, which was reversed by HMGB1 overexpression.

CONCLUSIONS

QA regulated the gut-liver lipid metabolism and chronic vascular inflammation of TMA/TMAO through gut microbiota to inhibit the atherogenesis in Apoe-/- mice, and the mechanism may be related to the HMGB1/SREBP2 pathway.

Uncovering the key pharmacodynamic material basis and possible molecular mechanism of Xiaoke formulation improve insulin resistant through a comprehensive investigation

ETHNOPHARMACOLOGICAL RELEVANCE

Xiaoke formulation (XKF) has been utilized in clinical practice for decades in China as a treatment option for mild to moderate type 2 diabetes. However, there is still a need for systematic research to uncover the key pharmacodynamic material basis and mechanism of XKF.

AIM OF THE STUDY

Aim of to investigate the distribution and metabolism of XKF in normal and insulin resistant (IR) mice were different, and elucidate its key pharmacodynamic material basis and mechanism of action.

MATERIALS AND METHODS

Ultra performance liquid chromatography/time of flight mass spectrometry technology was employed to investigate the differences in XKF absorption, distribution, and metabolism between normal and IR mice across blood, liver, feces, and urine samples. Further, network pharmacology was used to predict target proteins and their associated signaling pathways. Then, molecular docking was utilized to validate the activity of key pharmacodynamic components and targets. Finally, IR HepG2 cells were used to detect the glucose consumption under the action of key pharmacodynamic material basis. In addition, the expression of phosphatidylinositol 3-kinase (PI3K), protein kinase B (AKT) and phospho-protein kinase B (p-AKT) was determined using western blotting.

RESULTS

The study demonstrates significant distinctions in plasma and liver number and abundance of alkaloids, organic acids, flavonoids, iridoids and saponins between normal and IR mice when XKF was administered. Further analysis has shown that the representative components of XKF, including berberine, chlorogenic acid, calycosin, swertiamarin and astragaloside IV have significantly different metabolic pathways in plasma and liver. Prototypes and metabolites of these components were rarely detected in the urine and feces of mice. According to the network pharmacological analysis, these differential components are predicted to improve IR by targeting key factors such as SRC, JUN, HRAS, NOS3, FGF2, etc. Additionally, the signaling pathways involved in this process include PI3K-AKT pathway, GnRH signaling pathway, and T cell receptor signaling pathway. In addition, in vitro experiments indicate that berberine and its metabolites (berberine and demethyleneberine), chlorogenic acid and its metabolites (3-O-ferulic quinic acid and 5-O-ferulic quinic acid), calycosin and swertiamarin could improve IR in IR-HepG2 cells by elevating the expression of PI3K and AKT, leading to an increase in glucose consumption.

CONCLUSION

The key pharmacodynamic material basis of XKF, such as berberine and its metabolites (berberrubine and demethyleneberberine), chlorogenic acid and its metabolites (3-O-feruloylquinic acid and 5-O-feruloylquinic acid), calycosin and swertiamarin influence the glucose metabolism disorder of IR-HepG2 cells by regulating the PI3K/AKT signalling pathway, leading to an improvement in IR.

Profile of Phenolic Compounds and Antioxidant Activity of Celery (Apium graveolens) Juices Obtained from Pulp after α-Amylase Treatment from Aspergillus oryzae

The purpose of this study was to determine the content of certain phenolic compounds, antioxidant activity, pressing efficiency, extract content, and sugars in celeriac juices obtained from the pulp after α-amylase treatment from Aspergillus oryzae. The test material consisted of peeled and unpeeled celery pulp kept at a temperature of 25 °C with and without the enzyme for a period of 30 and 60 min. The juices obtained from them were analyzed for the content of selected phenolic acids and flavonoids using the UPLC-PDA-ESI-MS/MS method, for antioxidant activity measured using the ABTS˙+ and DPPH˙ method, and for the total polyphenol content using the F-C method. Additionally, the juice pressing efficiency, the extract content using the refractometer method, and the sugar content using the HPLC method were checked. Significantly higher antioxidant activity, pressing yield, and average content of caffeic acid glucoside, quinic acid, kaempferol-3,7-di-O-glucoside, and chrysoeriol-7-O-apiosylglucoside were obtained in juices from peeled celery. Maceration of the pulp with amylase resulted in a significant reduction in antioxidant activity compared to control samples. An is-total increase of 17-41% in total flavonoid content was observed in all juices tested after treatment with the enzyme for 30 and 60 min, and the phenolic acid content increased by 4-41% after treatment of the pulp with amylase for 60 min. The 60 min holding of the pulp at 25 °C, including with the enzyme, was shown to decrease the antioxidant activity and the content of quinic acid, ferulic acid, and chrysoriol-7-O-apiose-glucoside in the juices tested compared to the samples held for 30 min, while the content of other phenolic acids and flavonoids increased. In addition, after 60 min of enzymatic maceration, the pressing yield of the juices increased.

High-Level Biosynthesis of Chlorogenic Acid from Mixed Carbon Sources of Xylose and Glucose through a Rationally Refactored Pathway Network

Chlorogenic acid (CGA) has incredible potential for various pharmaceutical, nutraceutical, and agricultural applications. However, the traditional extraction approach from plants is time-consuming, further limiting its production. Herein, we design and construct the de novo biosynthesis pathway of CGA using modular coculture engineering in Escherichia coli, which is composed of MG09 and BD07 strains. To accomplish this, the phenylalanine-deficient MG09 strain was engineered to utilize xylose preferentially and to overproduce precursor caffeic acid, while the tyrosine-deficient BD07 strain was constructed to consume glucose exclusively to enhance another precursor quinic acid availability for the biosynthesis of CGA. Further pathway modularization and balancing in the context of syntrophic cocultures resulted in additional production improvement. The coculture strategy avoids metabolic flux competition in the biosynthesis of two CGA precursors, caffeic acid and quinic acid, and allows for production improvement by balancing module proportions. Finally, the optimized coculture based on the aforementioned efforts produced 131.31 ± 7.89 mg/L CGA. Overall, the modular coculture engineering strategy in this study provides a reference for constructing microbial cell factories that can efficiently biomanufacture complex natural products.

[Screening of bioactive components endowing hawthorn with turbidity-eliminating and lipid-lowering functions and development of quality control method of hawthorn]

Hawthorn has the efficacy of eliminating turbidity and lowering the blood lipid level, and it is used for treating hyperlipidemia in clinic. However, the bioactive components of hawthorn are still unclear. In this study, the spectrum-effect relationship was employed to screen the bioactive components of hawthorn in the treatment of hyperlipidemia, and then the bioactive components screened out were verified in vivo. Furthermore, the quality control method for hawthorn was developed based on liquid chromatography-mass spectrometry(LC-MS). The hyperlipidemia model of rats was built, and different polar fractions of hawthorn extracts and their combinations were administrated by gavage. The effects of different hawthorn extract fractions on the total cholesterol(TC), triglycerides(TG), and low-density lipoprotein-cholesterol(LDL-C) in the serum of model rats were studied. The orthogonal projections to latent structures(OPLS) algorithm was used to establish the spectrum-effect relationship model between the 24 chemical components of hawthorn and the pharmacodynamic indexes, and the bioactive components were screened out and verified in vivo. Finally, 10 chemical components of hawthorn, including citric acid and quinic acid, were selected to establish the method for evaluating hawthorn quality based on LC-MS. The results showed that different polar fractions of hawthorn extracts and their combinations regulated the TG, TC, and LDL-C levels in the serum of the model rats. The bioactive components of hawthorn screened by the OPLS model were vitexin-4″-O-glucoside, vitexin-2″-O-rhamnoside, rutin, citric acid, malic acid, and quinic acid. The 10 chemical components of hawthorn, i.e., citric acid, quinic acid, rutin, gallic acid, vitexin-4″-O-glucoside, vitexin-2″-O-rhamnoside, malic acid, vanillic acid, neochlorogenic acid, and fumaric acid were determined, with the average content of 38, 11, 0.018, 0.009 5, 0.037, 0.017, 8.1, 0.009 5, 0.073, and 0.98 mg·g~(-1), respectively. This study provided a scientific basis for elucidating the material basis of hawthorn in treating hyperlipidemia and developed a content determination method for evaluating the quality of hawthorn.

Acyl-quinic acids from the root bark of Acanthopanax gracilistylus and their inhibitory effects on neutrophil elastase and cyclooxygenase-2 in vitro

Eleven new acyl-quinic acids (AQAs) 1a-9, and 18 known AQAs 10-27 were isolated from the root bark of Acanthopanax gracilistylus W. W. Smith (Acanthopanacis Cortex). The planar structures of 1a-9 were determined based on their HR-ESIMS, IR, and NMR data. The absolute configurations of 1a-6 were identified by comparing the experimental and the calculated electronic circular dichroism (ECD) spectra. This is the first report of the isolation of AQAs from Acanthopanacis Cortex. Notably, 1a-6 were determined as unusual oxyneolignan-(-)-quinic acids heterodimers, representing a new class of natural products. The inhibitory activities of 1a-27 on neutrophil elastase (NE) and cyclooxygenase-2 (COX-2) were studied in vitro, and the results indicated they possessed significant inhibitory activities on COX-2. Among them, the IC50 values of 1a-9 were 0.63±0.014, 0.75±0.028, 0.15±0.023, 0.63±0.016, 0.30±0.013, 35.63±4.600, 8.70±1.241, 16.51±0.480, 0.69±0.049, 0.39±0.017, and 0.26±0.080 μM, respectively. This study represents the inaugural disclosure of the anti-COX-2 constituents found in Acanthopanacis Cortex, thereby furnishing valuable insights into the exploration of novel COX-2 inhibitors derived from natural reservoirs.

In-silico analysis reveals Quinic acid as a multitargeted inhibitor against Cervical Cancer

The cervix is the lowermost part of the uterus that connects to the vagina, and cervical cancer is a malignant cervix tumour. One of this cancer's most important risk factors is HPV infection. In the approach to finding an effective treatment for this disease, various works have been done around genomics and drug discovery. Finding the major altered genes was one of the most significant studies completed in the field of cervical cancer by TCGA (The Cancer Genome Atlas), and these genes are TGFBR2, MED1, ERBB3, CASP8, and HLA-A. The greatest genomic alterations were found in the PI3K/MAPK and TGF-Beta signalling pathways, suggesting that numerous therapeutic targets may come from these pathways in the future. We, therefore, conducted a combined enrichment analysis of genes gathered from various works of literature for this study. The final six key genes from the list were obtained after enrichment analysis using GO, KEGG, and Reactome methods. The six proteins against the identified genes were then subjected to a docking-based screening against a library of 6,87,843 prepared natural compounds from the ZINC15 database. The most stable compound was subsequently discovered through virtual screening to be the natural substance Quinic acid, which also had the highest binding affinity for all six proteins and a better docking score. To examine their stability, the study was extended to MM/GBSA and MD simulations on the six docked proteins, and comparative docking-based calculations led us to identify the Quinic Acid as a multitargeted compound. The overall deviation of the compound was less than 2 Å for all the complexes considered best for the biological molecules, and the simulation interaction analysis reveals a huge web of interaction during the simulation.Communicated by Ramaswamy H. Sarma.

Quinic acid ameliorates ulcerative colitis in rats, through the inhibition of two TLR4-NF-κB and NF-κB-INOS-NO signaling pathways

OBJECTIVE

In this study, the therapeutic effect of quinic acid (QA), which has anti-inflammatory activity, was investigated on acetic acid-induced colitis in male Wistar rats.

METHODS

Ulcerative colitis (UC) was induced in rats by acetic acid intrarectally, and the protective effects of QA in 10, 30, 60, and 100 mg/kg doses were investigated. Rats were treated for 5 days and their colon tissues were dissected out at the end. Macroscopic and histopathological examinations were performed in colon tissues. Also, the expression of inflammatory and apoptotic genes, including TLR4, IL-1β, INOS, IL-6, TNF-α, NF-κB, Caspase-3, Caspase-8, Bax, and Bcl-2, was measured. Biochemistry indices, such as malondialdehyde (MDA) and nitrite oxide (NO) content, in addition to, total antioxidant capacity (TAC), superoxide dismutase (SOD), catalase (CAT), and enzymes activities were also assessed.

RESULTS

Colitis increased the levels of MDA and NO, and enhanced the inflammatory and apoptotic gene expressions, while reducing the SOD and CAT enzymes activity, and TAC levels in the colitis rats. Also, results showed that colitis was associated with the infiltration of inflammatory cells, epithelium damage, and edema in colon tissue. QA significantly ameliorated histopathological indices, oxidative stress, inflammation, and apoptosis in colitis rats.

CONCLUSION

QA ameliorated UC through the inhibition of two TLR4-NF-κB and NF-κB-INOS-NO signaling pathways, which results in the reduction of colitis complications, including oxidative stress, inflammation, apoptosis and histopathological injuries in rats. Therefore it can be concluded, that QA exerts its therapeutic effects through antiapoptotic, antioxidant, and anti-inflammatory properties.

Chemical profile, antioxidant potential and toxicity of Smilax brasiliensis Sprengel (Smilacaceae) stems

Smilax brasiliensis Sprengel is a monocotyledon of the Smilacaceae family, native to the Brazilian Cerrado, popularly known as "salsaparrilha" or "japecanga". In this study, the ethanol extract (EE) and the hexane (HEXF), dichloromethane (DCMF), ethyl acetate (ACF), and hydroethanol (HEF) fractions of the stems were obtained. The chemical composition was determined, the contents of phenolic compounds and flavonoids were quantified, and the antioxidant potential and the cytotoxic effect on Artemia salina were evaluated. Fatty acid esters, hydrocarbons, and phytosterols were identified in the HEXF analyzed by gas chromatography - mass spectrometry (GC-MS). The EE and DCMF, ACF, and HEF were analyzed by liquid chromatography coupled to a diode array detector and mass spectrometer (LC-DAD-MS), and the identified constituents included glycosylated (rutin, 3-O-β-galactopyranosyl quercetin, 3-O-β-glucopyranosyl quercetin, O-deoxyhexosyl-hexosyl quercetin, O-deoxyhexosyl-hexosyl kaempferol, O-deoxyhexosyl-hexosyl O-methyl quercetin, and others), and non-glycosylated (quercetin) flavonoids, phenylpropanoids (3-O-E-caffeoyl quinic acid, 5-O-E-caffeoyl quinic acid, O-caffeoyl shikimic acid, and others), neolignan, steroidal saponin (dioscin), and N-feruloyltyramine. The EE, DCMF, and ACF showed high total contents of phenolic compounds (112.99, 175.71, and 524.02 µg of GAE/mg, respectively), and in the ACF and DCMF a great content of flavonoids was also quantified (50.08 and 31.49 µg of QE/mg, respectively). The EE, DCMF, ACF, and HEF exhibited great antioxidant potential by DPPH (IC₅₀ 1.71 - 32.83 µg/mL) and FRAP (IC₅₀ 0.63 - 6,71 µg/mL) assays. A maximum cytotoxic activity on A. salina of 60% was observed for the DCMF (LC₅₀ = 856.17 µg/mL). This study contributes to the phytochemical study of S. brasiliensis since these compounds were identified for the first time in the stems of this species. The S. brasiliensis stems demonstrated to be a rich source of polyphenols compounds and exhibited high antioxidant potential without toxicity. Thus, extract and fractions obtained from the S. brasiliensis stems can be used in food supplements or as natural antioxidants in the food industry.

Screening out Biomarkers of Tetrastigma hemsleyanum for Anti-Cancer and Anti-Inflammatory Based on Spectrum-Effect Relationship Coupled with UPLC-Q-TOF-MS

Tetrastigma hemsleyanum Diels et Gilg. (T. hemsleyanum) is an economically and medicinally valuable species within the genus Tetrastigma. However, the material basis of its pharmacological action and the biomarkers associated with its anti-cancer and anti-inflammatory effects are still unclear. Additionally, the T. hemsleyanum industry cannot grow because there is a lack of a scientific, universal, and measurable quality control system. This study aimed to explore the chemical basis quality markers related to the anti-cancer and anti-inflammatory effects of T. hemsleyanum to establish an effective quality evaluation method. UPLC-Q-TOF-MSE fingerprint profiles of T. hemsleyanum from different origins were established. Pharmacodynamic studies used HepG2 and HuH-7 cells and LPS-induced RAW264.7 to evaluate the anti-tumor and anti-inflammatory effects of the active ingredients. The spectrum-effect relationships between UPLC fingerprints and anti-cancer and anti-inflammatory activities were evaluated using PCA and PLSR statistical methods. Moreover, docking analysis was performed to identify specific active biomarkers with molecular targets associated with cancer and inflammation. Chlorogenic acid, quinic acid, catechin, kaempferol 3-rutinoside, apigenin-8-C-glucoside, and linolenic acid were associated with anticancer activity, while chlorogenic acid, quercetin, quinic acid, kaempferol 3-rutinoside, rutinum, apigenin-8-C-glucoside, and linolenic acid were associated with anti-inflammatory activity. The spectrum-effect relationship of T. hemsleyanum was successfully established, and the biomarkers for anti-cancer and anti-inflammatory effects were preliminary confirmed. These findings provide a theoretical basis for the elucidation of the substance basis of T. hemsleyanum and lay the foundation for its rapid identification, quality control, industrial research, and utilization.

Bioassay guided fractionation, isolation and characterization of hepatotherapeutic 1, 3-di-ortho-galloyl quinic acid from the methanol extract of the leaves of Pterocarpus santalinoides

ETHNOPHARMACOLOGICAL RELEVANCE

Leaf extracts of Pterocarpus santalinoides DC are traditionally used to ameliorate ageing-related ailments such as heart and liver diseases, and have been reported to be protective against toxic injuries to the liver.

AIM OF THE STUDY

This study aimed to isolate and characterize the hepatoprotective/hepatotherapeutic principle in the methanol leaf extract of P. santalinoides.

MATERIALS AND METHODS

Fresh leaves of P. santalinoides were dried under shade and ground into powder. The ground leaves (2 Kg) were extracted with 80% methanol by maceration. Fractionation was carried out using column and thin layer chromatography techniques. Bioassay of fractions and sub-fractions was done using carbon tetrachloride (CCl₄)-induced hepatotoxicity model in albino rats. Phytochemical analysis was carried out on the active compound. Characterization and structural elucidation of the active compound using high performance liquid chromatography and nuclear magnetic resonance spectroscopy was done.

RESULTS

Extraction yielded 260 g dry extract. Six fractions (F1, F2, F3, F4, F5 and F6) were obtained after column and thin layer chromatography, with F6 (R_f = 0.78; Yield = 2.13 g) being the most active hepatotherapeutic fraction that significantly (p < 0.05) lowered serum ALT activity and increased serum albumin levels in CCl₄-induced hepatopathy in albino rats. Further separation of F6 yielded four sub-fractions (F6_1, F6₂, F6₃ and F6₄), of which F6₁ with an R_f of 0.85 and a yield of 30.0 mg was isolated as the active hepatotherapeutic compound. Stiasny and ferric chloride test of F6₁ showed the presence of tannins in the fraction. Characterization of F6₁ revealed 1, 3-di-ortho-galloyl quinic acid.

CONCLUSION

The hepatoprotective/hepatotherapeutic principle in the methanol extract of the leaves of P. santalinoides was identified as 1, 3-di-ortho-galloyl quinic acid.

Callus Culture of Scorzonera radiata as a New, Highly Productive and Stable Source of Caffeoylquinic Acids

During our ongoing efforts to investigate biotechnological sources of caffeoylquinic acid (CQA) metabolites, we discovered the plant Scorzonera radiata Fisch. (Asteraceae), which is able to produce callus cultures with high yield and extremely high stability. An actively growing callus line, designated as Sr-L1, retained the ability to produce 11 CQAs during long-term cultivation (more than 20 years). A total of 29 polyphenolic compounds were identified in the leaves and Sr-L1 callus culture of S. radiata, including CQAs, lignol derivatives, flavonoids, and dihydrostilbenes. The composition of CQAs in the Sr-L1 culture was identical to that in the S. radiata leaves. Sr-L1 calli did not produce flavonoids and dihydrostilbenes, but produced lignol derivatives, which were absent in leaves. The HPLC-UV-HRMS determination showed the presence of monoacyl derivatives of CQAs such as 5-CQA, 4-CQA, cis-5-CQA, and 5-O-p-coumaroylquinic acid in the Sr-L1 culture. Among diacyl derivatives, 3,4-diCQA, 3,5-diCQA, cis-3,5-diCQA, 4,5-diCQA, 3-O-p-coumaroyl-5-O-CQA, and 3-O-caffeoyl-5-O-p-coumaroylquinic acid were found. The content of 5-CQA reached 7.54 mg/g dry weight and the content of 3,5-diCQA was as high as 18.52 mg/g dry weight. 3,5-diCQA has been reported to be of high nutritional and pharmacological value, as it alleviates inflammatory pain, reverses memory impairment by preventing neuronal apoptosis, and counteracts excessive adipose tissue expansion, serving as an attractive treatment option for obesity. The high content of 3,5-diCQA and the exceptional stability of biosynthesis make callus cultures of S. radiata a promising source for the development of drugs and nutraceuticals.

The chemical composition of the aerial parts of Stachys spreitzenhoferi (Lamiaceae) growing in Kythira Island (Greece), and their antioxidant, antimicrobial, and antiproliferative properties

The Stachys L. genus has been used in traditional medicine to treat skin inflammations, stomach disorders, and stress. The aim of this study was to investigate the chemical profile and biological activity of the methanolic extract of Stachys spreitzenhoferi Heldr. (Lamiaceae) aerial parts, collected on the island of Kythira, South Greece. The analysis by liquid chromatography coupled with electrospray ionization and high-resolution mass spectrometry [LC-(-)ESI/HRMSⁿ] of the methanol extract revealed the occurrence of thirty-six compounds - flavonoids, phenylethanoid glycosides, iridoids, quinic acid derivatives, aliphatic alcohol glycosides, and oligosaccharides - highlighting the substantial presence, as main peaks, of the iridoid melittoside (2) along with flavonoid compounds such as 4'-O-methylisoscutellarein mono-acetyl-diglycoside/chrysoeriol mono-acetyl-diglycoside (24), trimethoxy- (35) and tetramethoxyflavones (36). This extract was tested for its antimicrobial properties against Gram-positive and negative pathogenic strains. The extract was not active against Gram-negative bacteria tested, but it possessed a good dose-dependent antimicrobial activity towards S. aureus (MIC: 1.0 mg/mL) and L. monocytogenes (MIC: 1.0 mg/mL) Gram-(+) strains. Furthermore, this extract has been tested for its possible antioxidant activity in vitro. In particular, it has been shown that these molecules cause a decrease in DPPH, ABTS, and H₂O₂ radicals. The extract of S. spreitzenhoferi exhibited anti-DPPH activity (IC₅₀: 0.17 mg/mL), anti-H₂O₂ activity (IC₅₀: 0.125 mg/mL), and promising antiradical effect with an IC₅₀ value of 0.18 mg/mL for anti-ABTS activity. S. spreitzenhoferi extract caused a decrease in ROS (at the concentration of 200 μg/mL) and an increase in the activity of the antioxidant enzymes SOD, CAT, and GPX in OZ-stimulated PMNs. Furthermore, it exhibited antiproliferative activity against acute myeloid leukemia (U937 cell), causing 50% of cell death at the 0.75 mg/mL.

[Chemical constituents from Urtica dioica fruits]

The chemical constituents in Urtica dioica fruits were investigated by silica gel chromatography, preparative HPLC, NMR, and HR-MS for the first time. As a result, 21 compounds were isolated from the fruits of U. dioica and identified 7R,8S,8'R-olivil(1), oleic acid(2), α-linoleic acid(3), palmic acid(4), methyl palmitate(5), α-linolenic acid(6), α-linolenic acid methyl ester(7), 5-O-caffeoyl-shikimic acid(8), vanillic acid(9), p-coumaric acid(10), 5-O-p-coumaroylshikimic acid(11), cinnamic acid(12), quinic acid(13), shikimic acid(14), ethyl caffeate(15), coniferyl ferulate(16), ferulic acid(17), caffeic acid(18), chlorogenic acid(19), pinoresinol(20), and quercetin(21). Compound 1 was a new compound and compounds 2-16 were isolated from U. dioica for the first time.

Two new quinic acid derivatives from the leaves of Schisandra chinensis

Two new (1-2) and three known quinic acid derivatives (3-5) were isolated from the leaves of Schisandra chinensis (Turcz) Baill. The structures of the compounds were determined by spectroscopic methods, especially the NMR techniques, and also by comparison with reported data in the literature. The cytotoxicity activities of these compounds were evaluated on human tumor cell lines LN229 and three of them showed a certain activity.

Cell-free Biosynthesis of Chlorogenic Acid Using a Mixture of Chassis Cell Extracts and Purified Spy-Cyclized Enzymes

A novel cell-free biosynthesis system based on a mixture of chassis cell extracts and purified Spy-cyclized enzymes (CFBS-mixture) was developed. As a demonstration, the CFBS-mixture was applied to chlorogenic acid (CGA) biosynthesis. The mix-and-match and Plackett-Burman experiments demonstrated that Lonicera japonica hydroxycinnamate-CoA quinate transferase and p-hydroxyphenylacetate 3-hydroxylase were the key enzymes for the production of CGA. After optimization of the concentrations of the biosynthetic enzymes in the CFBS-mixture reaction using the Plackett-Burman experimental design and the path of the steepest ascent, 711.26 ± 15.63 mg/L CGA was produced after 16 h, which is 71.1-fold the yield obtained using the conventional crude extract-based CFBS and 9.1-fold the reported yield obtained using the living cells. Based on the CFBS-mixture results, the production of CGA was further enhanced in engineered Escherichia coli. The CFBS-mixture strategy is highly effective and will be useful for high-level CFBS of natural products.

In vitro inhibition of shikimate hydroxycinnamoyltransferase by acibenzolar acid, the first metabolite of the plant defence inducer acibenzolar-S-methyl

Acibenzolar acid, the first metabolite formed in planta from the defence inducer acibenzolar-S-methyl (ASM), has been shown to be an inhibitor of the enzyme shikimate hydroxycinnamoyltransferase (HST), extracted from grapevine or tobacco cell suspension cultures. Using a purified recombinant Arabidopsis thaliana HST, the inhibition was found to be competitive, acibenzolar acid binding reversibly to the shikimate binding site of the HST:p-coumaroyl-CoA complex, with a Ki value of 250 μM. The other hydroxycinnamoyltransferases tested in the course of this study, using either hydroxypalmitic acid, putrescine, tyramine, or quinic acid as acyl acceptors were not, or only slightly, inhibited by acibenzolar acid. To understand the specificity of the interaction of acibenzolar acid with HST, we analyzed the structure-activity relationship of a series of benzoic or acibenzolar acid analogues, tested either as AtHST substrates or as inhibitors. This analysis confirmed previously published data on the substrate flexibility of HST and demonstrated that both the carboxyl group and the thiadiazole moiety of acibenzolar acid are playing an important role in the interaction with the shikimate binding site. Acibenzolar acid, which cannot form an ester bond with p-coumaric acid, was however a less potent inhibitor than protocatechuic or 3-hydroxybenzoic acids, which are used as acyl acceptors by HST. Our results show that the interaction of acibenzolar acid with HST, which is probably directly linked to the substrate promiscuity of HST, is unlikely to play a direct role in the defence-inducing properties of ASM in plants.

De Novo Biosynthesis of Chlorogenic Acid Using an Artificial Microbial Community

Engineering an artificial microbial community for natural product production is a promising strategy. As mono- and dual-culture systems only gave non-detectable or minimal chlorogenic acid (CGA) biosynthesis, here, a polyculture of three recombinant Escherichia coli strains, acting as biosynthetic modules of caffeic acid (CA), quinic acid (QA), and CGA, was designed and used for de novo CGA biosynthesis. An influx transporter of 3-dehydroshikimic acid (DHS)/shikimic acid (SA), ShiA, was introduced into the QA module-a DHS auxotroph. The QA module proportion in the polyculture and CGA production were found to be dependent on ShiA expression, providing an alternative approach for controlling microbial community composition. The polyculture strategy avoids metabolic flux competition in the biosynthesis of two CGA precursors, CA and QA, and allows production improvement by balancing module proportions. The performance of this polyculture approach was superior to that of previously reported approaches of de novo CGA production.

Characterization and quantification of hydroxycinnamate derivatives in Stevia rebaudiana leaves by LC-MSn

Stevia rebaudiana leaves are used as a zero-calorie natural sweetener in a variety of food products in Asian countries, especially in Japan. In this study, the hydroxycinnamate derivatives of S. rebaudiana have been investigated qualitatively and quantitatively by LC-MSn. Twenty-four hydroxycinnamic acid derivatives of quinic and shikimic acid were detected, and 19 of them were successfully characterized to regioisomeric levels; 23 are reported for the first time from this source. These comprise three monocaffeoylquinic acids (Mr 354), seven dicaffeoylquinic acids (Mr 516), one p-coumaroylquinic acid (Mr 338), one feruloylquinic acid (Mr 368), two caffeoyl-feruloylquinic acids (Mr 530), three caffeoylshikimic acids (Mr 336), and two tricaffeoylquinic acids (Mr 678). Cis isomers of di- and tricaffeoylquinic acids were observed as well. Three tricaffeoylquinic acids identified in stevia leaves are reported for the first time in nature. These phenolic compounds identified in stevia might affect the organoleptic properties and add additional beneficial health effects to stevia-based products.

Characterization by LC-MS(n) of four new classes of chlorogenic acids in green coffee beans: dimethoxycinnamoylquinic acids, diferuloylquinic acids, caffeoyl-dimethoxycinnamoylquinic acids, and feruloyl-dimethoxycinnamoylquinic acids

LC-MS4 has been used to detect and characterize in green coffee beans 12 chlorogenic acids not previously reported in nature. These comprise three isomeric dimethoxycinnamoylquinic acids (7-9) (Mr 382), three caffeoyl-dimethoxycinnamoylquinic acids (22, 24, and 26) (Mr 544), three diferuloylquinic acids (13-15) (Mr 544), and three feruloyl-dimethoxycinnamoylquinic acids (28, 30, and 32) (Mr 558). Structures have been assigned on the basis of LC-MS4 patterns of fragmentation and relative hydrophobicity and, in the case of the dimethoxycinnamoylquinic acids, by comparison with authentic standards. Several new structure-diagnostic fragmentations have been identified for use with diacyl-chlorogenic acids, for example, m/z 299 and 255 for C4 caffeoyl, m/z 313 and 269 for C4 feruloyl, nearly equal elimination of both cinnamoyl residues for vic-3,4-diacyl, and an increasing ratio of "dehydrated" ions to "non-dehydrated" ions at MS2 with increasing methylation of those cinnamoyl residues. Possible mechanisms have been proposed to account for the fragmentations observed. The mass spectrometric resolution of six isomeric chlorogenic acids (Mr 544) in a crude plant extract by fragment-targeted LC-MS2 and LC-MS3 experiments illustrates the analytical power and advantage of ion trap mass spectroscopy.

Site-directed Mutagenesis of the Active Site Region in the Quinate/Shikimate 5-Dehydrogenase YdiB of Escherichia coli

YdiB and its paralog AroE are members of the quinate/shikimate 5-dehdrogenase family. Enzymes from this family function in the shikimate pathway that is essential for survival of microorganisms and plants and represent potential drug targets. Recent YdiB and AroE crystal structures revealed the presence of a NAD(P)-binding and a catalytic domain. We carried out site-directed mutagenesis of 8 putative active site residues in YdiB from Escherichia coli and analyzed structural and kinetic properties of the mutant enzymes. Our data indicate critical roles for an invariant lysine and aspartate residue in substrate binding and allowed us to differentiate between two previously proposed models for the binding of the substrate in the active site. Comparison of several YdiB and AroE structures led us to conclude that, upon cofactor binding and domain closure, the 2 identified binding residues are repositioned to bind to the substrate. Although the lysine residue contributes to some extent to the stabilization of the transition state, we did not identify any residue as catalytically essential. This indicates that catalysis does not operate through a general acid-base mechanism, as thought originally. Our improved understanding of the medically and agriculturally important quinate/shikimate 5-dehydrogenase family at the molecular level may prove useful in the development of novel herbicides and antimicrobial agents.

UTILIZATION OF AROMATIC AMINO ACIDS BY HYDROGENOMONAS FACILIS

DeCicco, B. T. (Rutgers, The State University, New Brunswick, N.J.), and W. W. Umbreit. Utilization of aromatic amino acids by Hydrogenomonas facilis. J. Bacteriol. 88:1590-1594. 1964.-An auxotrophic mutant of Hydrogenomonas facilis was isolated which requires tryptophan, phenylalanine, and p-aminobenzoic acid (PABA) for growth. With glucose as the main carbon and energy source, the quantitative requirements for tryptophan and PABA were at normal microgram levels, but the requirement for phenylalanine was very large and approached substrate concentrations. The large phenylalanine requirement is due to a rapid oxidation and degradation of phenylalanine by the mutant. The utilization of both phenylalanine and glucose is adaptive, and the presence of phenylalanine partially inhibits the induction of the glucose-utilizing system. Wild-type H. facilis can utilize either phenylalanine or tyrosine for growth. Tracer studies indicated that during growth on phenylalanine, the aromatic ring is opened and degraded. Wild-type cells grown on either phenylalanine or tyrosine can oxidize phenylalanine, tyrosine, or phenylpyruvate without a lag. Another inducible pathway enables H. facilis to utilize either quinate or 3,4-dihydroxybenzoate for growth, and sequential adaptation studies revealed that quinate is converted to 3,4-dihydroxybenzoate during its degradation. Mutants may be obtained which can also utilize 2,5-dihydroxybenzoate for growth.

BIOGENESIS OF THE N-METHYL GROUP OF PYOCYANINE

L-Methionine-methyl-C14 or L-serine-3-C14 was added in substrate amount to a medium containing D-quinic acid, glycerol, L-alanine, and salts. Pseudomonas aeruginosa was grown on this medium, and the pyocyanine synthesized by the organism was isolated and degraded to give an estimate of radioactivity in the N-methyl carbon atoms. The methyl carbon atoms of methionine added to the medium supplied 66% of the N-methyl carbon atoms of pyocyanine and were not incorporated to any extent into the rest of the pyocyanine molecule. This was true even though this strain of P. aeruginosa did not require an exogenous supply of methionine to synthesize pyocyanine. The addition of unlabelled serine to the medium did not decrease the incorporation of the methyl carbon atoms of methionine into the N-methyl carbon atoms of pyocyanine. The labelled carbon atoms of serine-3-C14 were incorporated to a lesser extent and less specifically into the N-methyl carbon atoms of pyocyanine than were the methyl carbon atoms of methionine.

Molecular characterization of the qa-4 gene of Neurospora crassa

The qa-4 gene of Neurospora crassa encodes 3-dehydroshikimate dehydratase, which catalyzes the third step of the quinic acid (qa) catabolic pathway. The enzyme has previously been purified and characterized as a monomer of approx. 37 kDal. The nucleotide sequence of the qa-4 gene is presented here and the amino acid composition and tentative NH2-terminal sequence confirm the identification of the coding region within the qa-4 DNA sequence. There are no introns in the qa-4 coding region. By S1 nuclease mapping and primer extension analysis three distinct regions of transcription initiation were identified. Heterogeneity was also observed in the 3' ends of qa-4 mRNA. 5' and 3' untranslated regions of the qa-4 gene were compared with the corresponding regions in other Neurospora genes. Genomic blot analysis of twenty previously isolated qa-4 mutants revealed that two mutants, MC150 and MC191, have restriction patterns altered from wild type. In each strain the alteration occurs in the 3' half of the qa-4 coding region.

Organization of the qa gene cluster in Neurospora crassa: direction of transcription of the qa-3 gene

In Neurospora crassa, the enzyme quinate (shikimate) dehydrogenase catalyzes the first reaction in the inducible quinic acid catabolic pathway and is encoded in the qa-3 gene of the qa cluster. In this cluster, the order of genes has been established as qa-1 qa-3 qa-4 qa-2. Amino-terminal sequences have been determined for purified quinate dehydrogenase from wild type and from UV-induced revertants in two different qa-3 mutants. These two mutants (M16 and M45) map at opposite ends of the qa-3 locus. In addition, mapping data (Caseet al. 1978) indicate that the end of the qa-3 gene specified by M45 is closer to the adjacent qa-1 gene than is the end specified by the M16 mutant site. In one of the revertants (R45 from qa-3 mutant M45), the aminoterminal sequence for the first ten amino acids is identical to that of wild type. The other revertant (R1 from qa-3 mutant M16) differs from wild type at the amino-terminal end by a single altered residue at position three in the sequence. The observed change involves the substitution of an isoleucine in M16-R1 for a proline in wild type. This substitution requires a two-nucleotide change in the corresponding wild-type codon.--The combined genetic and biochemical data indicate that the qa-3 mutants M16 and M45 carry amino acid substitutions near the amino-terminal and carboxyl-terminal ends of the quinate dehydrogenase enzyme, respectively. On this basis we conclude that transcription of the qa-3 gene proceeds from the end specified by the M16 mutant site in the direction of the qa-1 gene. It appears probable that transcription is initiated from a promoter site within the qa cluster, possibly immediately adjacent to the qa-3 gene.

Genetical and biochemical characterization of QA-3 mutants and revertants in the QA gene cluster of Neurospora crassa

The qa-3 gene, one of the four genes in the qa gene cluster, encodes quinate (shikimate) dehydrogenase (quinate: NAD oxidoreductase, ER 1.1.1.24), the first enzyme in the inducible quinic acid catabolic pathway in Neurospora crassa. Genetic analyses have localized 26 qa-3 mutants at 11 sites on the aq-3 genetic map on the basis of prototroph frequencies. Certain mutants, e.g., 336-3-10 and 336-3-3, are located at opposite ends of the qa-3 gene. Data from four-point crosses (qa-1s mutant 124 X five different qa-3 mutants in triple mutants qa-3, qa-4, qa-2) indicate the following orientation of the qa-3 gene within the qa cluster; qa-1, qa-3 mutant 336-3-10 ("left" end) qa-3 mutant 336-3-3 ("right" end), qa-4, qa-2. Ultraviolet-induced revertants have been obtained from 14 of the qa-3 mutants. The revertable mutants fall into two major classes: those that revert by changes either at the same site or at a second site within the qa-3 gene, and those that revert by unlinked suppressor mutations. The intragenic revertants can be further distinguished by quantative and/or qualitative differences in their quinate dehydrogenase activities. Some revertants with activities either equivalent to or less than wild type produce a thermostable enzyme, and others an enzyme which is thermolabile in vitro at 35 degrees. A concentration of quinic acid or shikimic acid as low as 50 micron protects the enzyme markedly from heat inactivation. The genetic organization and the orientation of the qa-3 gene are discussed with respect to its direction of transcription and to the possible localization of a promoter (initiator) region(s) within the qa gene cluster.

Purification and characterization of quinate (shikimate) dehydrogenase, an enzyme in the inducible quinic acid catabolic pathway of Neurospora crassa

The bifunctional enzyme quinate (shikimate) dehydrogenase (quinate: NAD+ oxidoreductase, EC 1.1.1.24), which catalyzes the first reaction in the inducible quinic acid catabolic pathway of Neurospora crassa, has been purified to homogeneity. The enzyme is a monomer of 41000 daltons with an s20,w = 2.94 S. However, electrophoresis under non-denaturing conditions revealed three protein species, which have both quinate and shikimate dehydrogenase activities. The enzyme, with a single binding site for both substrates, has a Km of 0.37 mM for quinate and of 1.18 mM for shikimate, although the V is about 3-fold higher with shikimate. Essential sulphydryl groups which were not localized in the active site were detected. Thermal stability of the enzyme was greatly enhanced by low concentrations of quinate, shikimate, NADH, or by high ionic strength.

Quinate metabolism in Pseudomonas aeruginosa

Data obtained with the Warburg constant-volume respirometer and from enzyme analysis have demonstrated that the method of regulation of the "hydroaromatic" degradation pathway found in Pseudomonas aeruginosa is vastly different from that previously discovered in Acinetobacter calcoaceticus and perhaps also significantly different from P. putida. Two mutants have been analyzed: the first with multiple impairment of degradative abilities; the second with a single defect, i.e. a lack of quinic dehydrogenase activity. Quinic dehydrogenase has also been shown to function for shikimate utilization in P. aeruginosa, even though 5-dehydroshikimate reductase in vitro catalyzes the same reaction. The possible relationship of these findings to pyocyanine formation is discussed.

Repression of aromatic amino acid biosynthesis in Escherichia coli K-12

Mutants of Escherichia coli K-12 were isolated in which the synthesis of the following, normally repressible enzymes of aromatic biosynthesis was constitutive: 3-deoxy-d-arabinoheptulosonic acid 7-phosphate (DAHP) synthetases (phe and tyr), chorismate mutase T-prephenate dehydrogenase, and transaminase A. In the wild type, DAHP synthetase (phe) was multivalently repressed by phenylalanine plus tryptophan, whereas DAHP synthetase (tyr), chorismate mutase T-prephenate dehydrogenase, and transaminase A were repressed by tyrosine. DAHP synthetase (tyr) and chorismate mutase T-prephenate dehydrogenase were also repressed by phenylalanine in high concentration (10(-3)m). Besides the constitutive synthesis of DAHP synthetase (phe), the mutants had the same phenotype as strains mutated in the tyrosine regulatory gene tyrR. The mutations causing this phenotype were cotransducible with trpA, trpE, cysB, and pyrF and mapped in the same region as tyrR at approximately 26 min on the chromosome. It is concluded that these mutations may be alleles of the tyrR gene and that synthesis of the enzymes listed above is controlled by this gene. Chorismate mutase P and prephenate dehydratase activities which are carried on a single protein were repressed by phenylalanine alone and were not controlled by tyrR. Formation of this protein is presumed to be controlled by a separate, unknown regulator gene. The heat-stable phenylalanine transaminase and two enzymes of the common aromatic pathway, 5-dehydroquinate synthetase and 5-dehydroquinase, were not repressible under the conditions studied and were not affected by tyrR. DAHP synthetase (trp) and tryptophan synthetase were repressed by tryptophan and have previously been shown to be under the control of the trpR regulatory gene. These enzymes also were unaffected by tyrR.

Mechanism and stereochemistry of 5-dehydroquinate synthetase

3-Deoxy-D-arabino-heptulosonic acid 7-phosphate (DAHP) labeled at C-7 randomly or stereospecifically with tritium and at C-1 with (14)C was converted enzymically to 5-dehydroquinate. Tritium of all three substrates was completely retained in 5-dehydroquinate, in accord with formation of a non-ketonizing 6,7-enol intermediate. The 5-dehydroquinates were dehydrated to 5-dehydroshikimate by 5-dehydroquinate dehydratase, which is known to catalyze a cis-elimination. Only 5-dehydroquinate derived from [7-(3)H](7R)-DAHP lost its tritium in this dehydration, indicating that the configuration at C-7 was inverted in the conversion of DAHP to 5-dehydroquinate.

The urinary aromatic acids excreted by sheep given S24 perennial ryegrass cut at six stages of maturity

1. S 24 perennial ryegrass was harvested at six stages of its growth from young leafy herbage to mature grass in which the seed had shed.

2. Two sheep were offered 1kg/d of each cut and two other sheep were offered 750 g/d of each cut of grass.

3. The contents of some possible precursors of the urinary aromatic acids excreted by sheep, namely, shikimic acid, quinic acid, chlorogenic acid, total o-dihydroxyphenolic compounds, lignin and crude protein were determined in each cut of grass.

4. A gas-liquid chromatographic method for the determination of the aromatic acids present in light petroleum extracts of urine was developed.

5. The urinary excretion of creatinine, diethyl ether-soluble acids, hippuric acid, total benzoic, phenylacetic and phenylpropionic acids, and the apparent digestibilities of nitrogen, lignin and dry matter were determined with each sheep offered each cut of grass.

6. The quantity of the various aromatic acid fractions excreted by sheep decreased as the maturity of the herbage increased and was directly proportional to the amount of food consumed.

7. No relationship was found between the intake of possible benzoic acid precursors and the urinary excretion of benzoic acid. With diets of young herbage, smaller amounts of benzoic acid were excreted in the urine than would be predicted from the intakes of the precursors studied, and with mature herbage greater amounts were excreted than would be predicted.

8. Possible reasons for these results are discussed, and the nature of additional precursors of urinary aromatic acids excreted by sheep given mature herbages are considered.

9. Urinary excretion of phenylacetic acid varied with diet in a manner which closely followed the intake of apparently digestible nitrogen. A highly significant (P < 0.001) exponential relationship was found between these two variables; it was log10E = 0.05 N –0.63, where E is the urinary phenylacetic acid output (g/kg food) and N the intake of apparently digestible nitrogen (g/kg food).

Biosynthesis of scopolin in tobacco

[2-14C]Ferulic acid was fed to tobacco leaves and the radioactive products isolated after 6, 24, and 72 h of metabolism were studied. About half the fed activity was rapidly converted to water-soluble compounds. Feruloylglucose and an ester of ferulic acid glucoside were quickly formed, the former being subsequently incorporated into the fiber and the latter giving rise to scopolin. It is proposed that a ferulic acid glucoside derivative is the natural precursor of scopolin in tobacco.