Enzymatic Synthesis and Characterization of Mono-, Oligo-, and Polyglucosylated Conjugates of Caffeic Acid and Gallic Acid

Effects of potential allelochemicals in a water extract of Abutilon theophrasti Medik. on germination and growth of Glycine max L., Triticum aestivum L., and Zea mays L

BACKGROUND

Velvetleaf (Abutilon theophrasti Medik.), primarily a cropland weed, exerts adverse impacts on the productivity of various crops, including soybean (Glycine max L.), wheat (Triticum aestivum L.), and maize (Zea mays L.), by hindering their vegetative growth. However, the interference mechanism of velvetleaf on the three crops remains unclear.

RESULTS

The inhibitory effect of velvetleaf water extract on the germination and growth of soybean, wheat, and maize was determined in pot experiments and field trials. Four phenolic acids were identified as allelochemicals: protocatechuic acid (PA), gallic acid (GA), chlorogenic acid (CHA), and vanillic acid (VA). These allelochemicals were detected in different parts (leaves, roots, and stems) of velvetleaf, and in the rhizosphere soil of tested crops over the range of 1.19-556.23 μm kg^-1 . These allelochemicals were administered in approximate concentrations as in velvetleaf roots and rhizosphere soil, and their effects varied with crop species and velvetleaf parts. The allelochemicals generally had low-dose stimulation and high-dose inhibition effects on the growth of soybean, wheat, and maize. Furthermore, the biomass distribution of these crops was affected by allelochemicals in the soil. In field trials, the allelochemicals significantly (P < 0.05) inhibited the growth of all tested crops over the whole growth period, and PA showed a significant (P < 0.05) inhibitory effect on the yield of soybean, wheat, and maize.

CONCLUSION

GA, PA, CHA, and VA in velvetleaf aqueous extracts were identified as allelochemicals that play an inhibitory role on three crops. © 2022 Society of Chemical Industry.

The anti-aging effects of Renshen Guben on thyrotoxicosis mice: Improving immunosenescence, hypoproteinemia, lipotoxicity, and intestinal flora

With the rapid aging of the population, the control of age-related disease susceptibility and prognosis faces greater challenges. There is an urgent need for a strategy to maintain the vitality of elderly people. In this study, the effect of Renshen Guben (RSGB) oral liquid was investigated on an accelerated aging mice model of thyrotoxicosis by conventional detection methods combined with multiomics technology. The results showed that RSGB increased the number of neutrophils and lymphocytes, enhanced the function of lymphocytes, and increased the levels of complement and antimicrobial peptides, which indicated that RSGB improved the immunity of thyrotoxicosis mice at the cellular and molecular levels. RSGB corrected malnutrition in thyrotoxicosis mice by improving anemia, hypoalbuminemia, ion transporters, and vitamin-binding proteins. RSGB significantly reduced the lipotoxicity by reducing the level of fatty acids, triglyceride, sphingolipids, and glucocorticoids, thus increasing the level of docosapentaenoic acid (DPA) and bile acids, which contributed to improve immunosenescence. The intestinal defense ability of thyrotoxicosis mice was enhanced with the increase of bile acids and lactic acid bacteria by the RSGB treatment. The plant metabolomics analysis showed that there were various active components in RSGB oral liquid and medicated serum, including terpenoids, phenolic acids, flavonoids, tannin, alkaloids, organic acids, phenolamines, amino acids, and others. They have antioxidant, immune regulation, and anti-aging effects, which was the material basis of RSGB. Totally, RSGB protected the thyrotoxicosis mice against aging by improving immunosenescence, hypoproteinemia, lipotoxicity, and the intestinal flora. It will be beneficial for improving the disease susceptibility and prognosis of the elderly.

Characterization of the (Engineered) Branching Sucrase GtfZ-CD2 from Apilactobacillus kunkeei for Efficient Glucosylation of Benzenediol Compounds

Branching sucrases, a subfamily of Glycoside Hydrolase family (GH70), display transglycosidase activity using sucrose as donor substrate to catalyze glucosylation reaction in the presence of suitable acceptor substrates. In this study, the (α1→3) branching sucrase GtfZ-CD2 from Apilactobacillus kunkeei DSM 12361 was demonstrated to glucosylate benzenediol compounds (i.e., catechol, resorcinol, and hydroquinone) to form monoglucoside and diglucoside products. The production and yield of catechol glucosylated products were significantly higher than that of resorcinol and hydroquinone, revealing a preference for adjacent aromatic hydroxyl groups in glucosylation. Amino residues around acceptor substrate binding subsite +1 were targeted for semirational mutagenesis, yielding GtfZ-CD2 variants with improved resorcinol and hydroquinone glucosylation. Mutant L1560Y with improved hydroquinone mono-glucosylated product synthesis allowed enzymatic conversion of hydroquinone into α-arbutin. This study thus revealed the high potential of GH70 branching sucrases for glucosylating noncarbohydrate molecules. IMPORTANCE Glycosylation represents one of the most important ways to expand the diversity of natural products and improve their physico-chemical properties. Aromatic polyphenol compounds widely found in plants are reported to exhibit various remarkable biological activities; however, they generally suffer from low solubility and stability, which can be improved by glycosylation. Our present study on the glucosylation of benzenediol compounds by GH70 branching sucrase GtfZ-CD2 and its semirational engineering to improve the glucosylation efficiency provides insight into the mechanism of acceptor substrates binding and its glucosylation selectivity. The results demonstrate the potential of using branching sucrase as an effective enzymatic glucosylation tool.

Caffeic Acid, an Active Ingredient in Coffee, Combines with DOX for Multitarget Combination Therapy of Lung Cancer

Adjuvant diet therapy is an important means of comprehensive treatment of cancer. It is recognized by patients for its high safety, painlessness, and ease to operate. However, the development of adjuvant dietary therapy is limited by unclear targets and unclear anticancer mechanisms. In this work, caffeic acid was found as an inhibitor of TMEM16A with an IC₅₀ of 29.47 ± 3.19 μM by fluorescence quenching and whole-cell patch-clamp experiments. Caffeic acid regulated the proliferation, migration, and apoptosis of lung cancer cells targeting TMEM16A, which was detected by CCK-8, colony formation, wound healing, and Annexin V assays. In addition, molecular docking combined with site-directed mutagenesis confirmed that the binding sites of caffeic acid to TMEM16A were D439, E448, and R753. Western blot results indicated that caffeic acid regulated the growth of lung cancer through the MAPK pathway. In vitro experiments showed that the inhibitory effect of caffeic acid combined with hydroxydaunorubicin (DOX) on lung cancer cell growth was better than a double concentration of any single dose. In vivo pharmacokinetic experiments and tumor xenograft experiments indicated that the combination of 5.4 mg/kg caffeic acid and 4.1 mg/kg DOX achieved 85.6% tumor suppression rate and offset the side effects. Therefore, caffeic acid is a safe and efficient antitumor active ingredient of food that can enhance the antitumor effect of DOX.

Enzymatic glucosylation of polyphenols using glucansucrases and branching sucrases of glycoside hydrolase family 70

Polyphenols exhibit various beneficial biological activities and represent very promising candidates as active compounds for food industry. However, the low solubility, poor stability and low bioavailability of polyphenols have severely limited their industrial applications. Enzymatic glycosylation is an effective way to improve the physicochemical properties of polyphenols. As efficient transglucosidases, glycoside hydrolase family 70 (GH70) glucansucrases naturally catalyze the synthesis of polysaccharides and oligosaccharides from sucrose. Notably, GH70 glucansucrases show broad acceptor substrate promiscuity and catalyze the glucosylation of a wide range of non-carbohydrate hydroxyl group-containing molecules, including benzenediol, phenolic acids, flavonoids and steviol glycosides. Branching sucrase enzymes, a newly established subfamily of GH70, are shown to possess a broader acceptor substrate binding pocket that acts efficiently for glucosylation of larger size polyphenols such as flavonoids. Here we present a comprehensive review of glucosylation of polyphenols using GH70 glucansucrase and branching sucrases. Their catalytic efficiency, the regioselectivity of glucosylation and the structure of generated products are described for these reactions. Moreover, enzyme engineering is effective for improving their catalytic efficiency and product specificity. The combined information provides novel insights on the glucosylation of polyphenols by GH70 glucansucrases and branching sucrases, and may promote their applications.