Sialidase Inhibitory Activity Research Articles

Sialidase Inhibitory Activity of Synthesized Biflavonoid Glycoconjugates

Sialidase Inhibitory Activity of Synthesized Biflavonoid Glycoconjugates

Testing for novel inhibitors of periodontitis-associated sialidases

The microorganisms associated with severe periodontitis are the periodontal pathogens of the red complex: Porphyromonas gingivalis, Tannerella forsythia and Treponema denticola. These organisms cleave sialic acids found at the terminal end of host glycoconjugates by hydrolysing the glycosidic linkages with their expressed sialidases, thereby affecting the integrity of the host periodontium and promoting disease progression. Both P. gingivalis (SiaPG) and T. forsythia (NanH) sialidase enzymes were purified using HisTag affinity chromatography and a range of putative synthetic and plant-based inhibitors were tested for their ability to inhibit both enzymes using a MUNANA cleavage assay. Investigation of sialidase inhibitory activity of these compounds revealed that the plant derived alkaloids: Epicatechin gallate (IC50 = 21.75μM and 120.9μM) and Berberine chloride (IC50 = 106.2μM and 125.5μM) were more effective inhibitors of both SiaPg and NanH enzymes than the anti-influenza drug Zanamivir, an FDA approved viral neuraminidase inhibitor. Finally, a range of newly synthesized sialic acid analogues were effective in the micromolar to nanomolar range against both SiaPg and NanH enzymes with compound 2e3aDFNeu5Ac9N3 having an IC50 of (3.846μM and 49.40nM) respectively. The data suggests several novel inhibitors of these enzymes that might have future use as novel drugs against diseases such as periodontitis, and which we are currently testing further in host-pathogen interaction studies.

Sialidase inhibitory activity of diarylnonanoid and neolignan compounds extracted from the seeds of Myristica fragrans

Sialidases are key virulence factors that remove sialic acid from host cell surface glycans, thus unmasking receptors to facilitate bacterial adherence and colonization. In this study, we report the isolation and characterization of novel inhibitors of the Streptococcus pneumoniae sialidases NanA, NanB, and NanC from Myristica fragrans seeds. Of the isolated compounds (1–12), malabaricone C showed the most pneumococcal sialidases inhibition (IC50 of 0.3μM for NanA, 3.6μM for NanB, and 2.9μM for NanC). These results suggested that malabaricone C and neolignans could be potential agents for combating S. pneumoniae infection agents.

Naringenin suppresses Edwardsiella tarda infection in GAKS cells by NanA sialidase inhibition

Edwardsiella tarda (E. tarda) is a gram-negative bacterium, which causes Edwardsiellosis in aquaculture. Previous studies indicate that E. tarda NanA sialidase plays crucial roles in infection through the desialylation of glycoproteins in fish cells. On the other hand, 2-deoxy-2,3-dehydro-N-acetylneuraminic acid, classic sialidase inhibitor, negatively regulates E. tarda infection of goldfish scale GAKS cells. Here, to development the suppression model of E. tarda infection for aquaculture application, the possibility of NanA inhibitory activities in citrus phytochemicals was evaluated as citrus extracts have widely been used as a supplement in fish diets for the improvement of meat quality. Some flavanones such as naringenin, hesperetin, hesperidin and naringin showed sialidase inhibitory activity toward recombinant NanA in vitro. Among them, naringenin showed the most potent inhibitory activity and its inhibitory pattern was non-competitive. Naringenin significantly suppressed E. tarda infection in GAKS cells at 200 and 400 μM without bactericidal effect on E. tarda. On the other hand, naringin, glycosylation form of naringenin, showed slight suppression of E. tarda infection toward GAKS cells, suggesting the glycosides on flavanone could be important for NanA inhibition. Fluorescence microscopy analysis verified that number of invading E. tarda in GAKS cells was declined by naringenin treatment. The present study exhibited the possibility of naringenin as an effective ingredient in fish diet for the inhibition of E. tarda infection.

A Novel Potent and Highly Specific Inhibitor against Influenza Viral N1-N9 Neuraminidases: Insight into Neuraminidase-Inhibitor Interactions.

People throughout the world continue to be at risk for death from influenza A virus, which is always creating a new variant. Here we present a new effective and specific anti-influenza viral neuraminidase (viNA) inhibitor, 9-cyclopropylcarbonylamino-4-guanidino-Neu5Ac2en (cPro-GUN). Like zanamivir, it is highly effective against N1-N9 avian and N1-N2 human viNAs, including H274Y oseltamivir-resistant N1 viNA, due to its C-6 portion still being anchored in the active site, different from the disruption of oseltamivir's C-6 anchoring by H274Y mutation. Unlike zanamivir, no sialidase inhibitory activity has been observed for cPro-GUN against huNeu1-huNeu4 enzymes. Broad efficacy of cPro-GUN against avian and human influenza viruses in cell cultures comparable to its sialidase inhibitory activities makes cPro-GUN ideal for further development for safe therapeutic or prophylactic use against both seasonal and pandemic influenza.

Synthesis and Evaluation of Influenza Virus Sialidase Inhibitory Activity of Hinokiflavone-Sialic Acid Conjugates

- The known biflavonoid, hinokiflavone (1) was isolated from the leaves of Metasequoia glyptostroboides Hu et Cheng and displayed influenza A and B virus sialidase inhibitory activity. The unnatural glycoconjugate, hinokiflavone-sialic acid (8) was synthesized and exhibited more potent inhibitory activity.

Synthesis and influenza virus sialidase inhibitory activity of analogues of 4-Guanidino-Neu5Ac2en (Zanamivir) modified in the glycerol side-chain

Analogues of 4-Guanidino-Neu5Ac2en (Zanamivir) have been prepared containing carbamate substituents at the 7-hydroxy position. (4S,5R,6R)-5-Acetylamino-6-{1R-[(6-aminohexyl)carbamoyloxy]-2R,3-dihydroxypropyl}-4-guanidino-5,6-dihydro-4H-pyran-2carboxylic acid and (4S,5R,6R)-5-Acetylamino-6-{1R-[heptylcarbamoyloxy]-2R,3-dihydroxypropyl}-4-guanidino-5,6-dihydro4H-pyran2-carboxylic acid were the two analogues possessing activity comparable to Zanamivir, showing potent inhibition of influenza virus sialidases and good antiviral activity in vitro.

Solution Phase Synthesis of Amide-Linked N-Acetyl Neuraminic Acid, α-Amino Acid, and Sugar Amino Acid Conjugates1

Peracetylated N-acetylneuraminic acid (NeuAc) was efficiently coupled to esters of glycine, alanine, and serine using BOP and HOBT in the presence of DIEA. Deprotection of the esters readied the NeuAc-α-amino acid conjugates for further elaboration. Coupling of the NeuAc-gly adduct with β-O-methoxy neuraminic acid methyl ester afforded a selectively protected glycine linked sialic acid dimer. 2-Amino-3,4-di-O-benzyl-(1→6)-anhydroglucose and alanine benzyl ester were also efficiently coupled to the bis adduct giving novel trimeric analogs. Elimination of the anomeric acetate from the NeuAc-gly dimer followed by global deprotection provided a novel saccharopeptide with modest clostridial sialidase inhibitory activity.

Synthesis and influenza virus sialidase inhibitory activity of analogues of 4-guanidino-Neu5Ac2en (GG167) with modified 5-substituents

Summary Analogues of 4-guanidino-Neu5Ac2en (GG167) have been prepared containing alternative amide and sulfonamide substituents at the 5-position. (4 S ,5 R ,6 R )-4-guanidino-5-(2,2,2-trifluoroacetylamino)-6-(1 R ,2 R , 3-trihydroxypropyl)-5,6-dihydro-4 H -pyran-2-carboxylic acid 5 and (4 S ,5 R ,6 R )-4-guanidino-5-methanesulfonylamino-6-(1 R ,2 R ,3-trihydroxypropyl)-5, 6-dihydro-4 H -pyran-2-carboxylic acid 6 were the only analogues which approached the activity of GG167, showing potent inhibition of influenza virus sialidases and good antiviral activity in vitro.

Synthesis and influenza virus sialidase inhibitory activity of the 5-desacetamido analogue of 2,3-didehydro-2,4-dideoxy-4-guanidinyl-N-acetylneuraminic acid (GG167)

The title compound 2b has been synthesised in 8 steps from 2-deoxy-D-glucose (2-DG). Key transformations were an aldolase reaction utilising 2-DG to form the 9 carbon sugar 3, and then introduction of the required unsaturation and a 4-amino substitutent in a one-pot process. The poor inhibitory activity of 2b demonstrates that the 5-acetamido substitutent in 2,3-didehydro-2,4-dideoxy-4-guanidinyl-N-acetylneuraminic acid (GG167) 1 is critical for sialidase binding.

In vivo anti-influenza virus activity of plant flavonoids possessing inhibitory activity for influenza virus sialidase

Isoscutellarein (5,7,8,4′-tetrahydroxyflavone) from the leaf of Scutellaria baicalensis non-competitively inhibited (IC 50, 20 μM) the hydrolysis of sodium p- nitrophenyl-N- acetyl-α- D - neuraminate by influenza virus sialidase with an apparent K i value of 41 μM. Negligible inhibitory activity was observed for mouse liver sialidase at a concentration of 79 μM. Isoscutellarein also inhibited the replication of influenza virus A/WSN/33 in Madin-Darby bovine kidney cells with 50% virus inhibitory dose at 16 nmol/well and influenza virus A/PR/8/34 in the allantoic sac of embryonated egg with little toxic effects. The flavone showed significant anti-influenza virus activity in vitro similar to isoscutellarein-8-methylether (F36) (Nagai, T., Miyaichi, Y., Tomimori, T., Suzuki, Y. and Yamada H., 1990, Chem. Pharm. Bull. 38, 1329–1332), and more potent virucidal activity in ovo than F36. However, F36 completely prevented proliferation of mouse-adapted influenza virus A/PR/8/34 in mouse lung by the intranasal (0.5 mg/kg) and intraperitoneal (4 mg/kg) administrations, and it was more potent than the known anti-influenza virus substance, amantadine. Intranasal administration of F36 (0.5 mg/kg) also protected mice against a lethal. influenza virus A/PR/8/34 infection. Isoscutellarein significantly inhibited lung virus proliferation when administered intranasally or orally to mice. F36 and isoscutellarein showed negligible toxic effect against mice. These results suggested that flavones, which have potent influenza virus sialidase inhibitory activity, have anti-influenza virus activity in vivo.

Inhibition of influenza virus sialidase and anti-influenza virus activity by plant flavonoids.

Flavonoids (103 species) were tested for inhibitory activity against influenza virus sialidase using sodium p-nitrophenyl-N-acetyl-alpha-D-neuraminate as substrate. 5,7,4'-Trihydroxy-8-methoxyflavone from the root of Scutellaria baicalensis showed the most potent activity (IC50, 55 microM), and this flavone appeared to be a non-competitive inhibitor of the enzyme. Whereas, negligible or weak inhibitory activities were observed for mouse liver sialidase, beta-galactosidase and alpha-mannosidase as tested. This flavone also inhibited the infection by influenza virus A/PR/8/34 of Madin-Darby canine kidney cells, and replication of the virus in the allantoic sack of embryonated egg. These results suggest that flavone, which has potent influenza virus sialidase inhibitory activity, may have anti-influenza virus activity.

Inhibition of mouse liver sialidase by the root of Scutellaria baicalensis.

Of 266 Chinese crude drugs, the hot water extract from the root of Scutellaria baicalensis showed potent mouse liver sialidase inhibitory activity; in addition, wogonin, wogonin glucuronide, baicalein, and baicalin were identified as the inhibitors. These flavonoids showed almost the same inhibitory activity when 50-125 micrograms/ml doses of the samples were used for the assay, while wogonin and baicalein showed a more potent activity than wogonin glucuronide and baicalin at the lower concentration (10 micrograms/ml). However, these flavonoids, except wogonin, showed negligible inhibitory activity against Arthrobacter ureafaciens sialidase. These results indicated that S. baicalensis extract contains the sialidase inhibitors which are specific to mouse liver sialidase.