In Vitro Anti-HIV-1 Activity of Fucoidans from Brown Algae.

Due to the developing resistance and intolerance to antiretroviral drugs, there is an urgent demand for alternative agents that can suppress the viral load in people living with human immunodeficiency virus (HIV). Recently, there has been increased interest in agents of marine origin such as, in particular, fucoidans to suppress HIV replication. In the present study, the anti-HIV-1 activity of fucoidans from the brown algae Alaria marginata, Alaria ochotensis, Laminaria longipes, Saccharina cichorioides, Saccharina gurianovae, and Tauya basicrassa was studied in vitro. The studied compounds were found to be able to inhibit HIV-1 replication at different stages of the virus life cycle. Herewith, all fucoidans exhibited significant antiviral activity by affecting the early stages of the virus-cell interaction. The fucoidan from Saccharina cichorioides showed the highest virus-inhibitory activity by blocking the virus' attachment to and entry into the host's cell, with a selectivity index (SI) > 160.

Polyphenols from Maackia amurensis Heartwood Protect Neuronal Cells from Oxidative Stress and Prevent Herpetic Infection.

Here, we continued the investigation of anti-HSV-1 activity and neuroprotective potential of 14 polyphenolic compounds isolated from Maackia amurensis heartwood. We determined the absolute configurations of asymmetric centers in scirpusin A (13) and maackiazin (10) as 7R,8R and 1″S,2″S, respectively. We showed that dimeric stilbens maackin (9) and scirpusin A (13) possessed the highest anti-HSV-1 activity among polyphenols 1-14. We also studied the effect of polyphenols 9 and 13 on the early stages of HSV-1 infection. Direct interaction with the virus (virucidal activity) was the main mechanism of the antiviral activity of these compounds. The neuroprotective potential of polyphenolic compounds from M. amurensis was studied using models of 6-hydroxydopamine (6-OHDA)-and paraquat (PQ)-induced neurotoxicity. A dimeric stilbene scirpusin A (13) and a flavonoid liquiritigenin (6) were shown to be the most active compounds among the tested polyphenols. These compounds significantly increased the viability of 6-OHDA-and PQ-treated Neuro-2a cells, elevated mitochondrial membrane potential and reduced the intracellular ROS level. We also found that scirpusin A (13), liquiritigenin (6) and retusin (3) considerably increased the percentage of live Neuro-2a cells and decreased the number of early apoptotic cells. Scirpusin A (13) was the most promising compound possessing both anti-HSV-1 activity and neuroprotective potential.

Physicochemical Properties and Antiherpetic Activity of κ-Carrageenan Complex with Chitosan.

Nanoparticles formation is one of the ways to modulate the physicochemical properties and enhance the activity of original polysaccharides. For this purpose, based on the polysaccharide of red algae, κ-carrageenan (κ-CRG), it polyelectrolyte complex (PEC), with chitosan, were obtained. The complex formation was confirmed by ultracentrifugation in a Percoll gradient, with dynamic light scattering. According to electron microscopy and DLS, PEC is dense spherical particles with sizes in the range of 150-250 nm. A decrease in the polydispersity of the initial CRG was detected after the PEC formation. Simultaneous exposure of Vero cells with the studied compounds and herpes simplex virus type 1 (HSV-1) showed that the PEC exhibited significant antiviral activity, effectively inhibiting the early stages of virus-cell interaction. A two-fold increase in the antiherpetic activity (selective index) of PEC compared to κ-CRG was shown, which may be due to a change in the physicochemical characteristics of κ-CRG in PEC.

Neuroprotective and Antiherpetic Properties of Polyphenolic Compounds from Maackia amurensis Heartwood.

In this study, we isolated a new isoflavanostilbene maackiapicevestitol (1) as a mixture of two stable conformers 1a and 1b as well as five previously known dimeric and monomeric stilbens: piceatannol (2), maackin (3), scirpusin A (4), maackiasine (5), and maackolin (6) from M. amurensis heartwood, using column chromatography on polyamide, silicagel, and C-18. The structures of these compounds were elucidated by NMR, HR-MS, and CD techniques. Maksar® obtained from M. amurensis heartwood and polyphenolics 1-6 possessed moderate anti-HSV-1 activity in cytopathic effect (CPE) inhibition and RT-PCR assays. A model of PQ-induced neurotoxicity was used to study the neuroprotective potential of polyphenolic compounds from M. amurensis. Maksar® showed the highest neuroprotective activity and increased cell viability by 18% at a concentration of 10 µg/mL. Maackolin (6) also effectively increased the viability of PQ-treated Neuro-2a cells and the value of mitochondrial membrane potential at concentrations up to 10 µΜ. Maksar® and compounds 1-6 possessed higher FRAP and DPPH-scavenging effects than quercetin. However, only compounds 1 and 4 at concentrations of 10 µM as well as Maksar® (10 µg/mL) statistically significantly reduced the level of intracellular ROS in PQ-treated Neuro-2a cells.

The Comparative Analysis of Antiviral Activity of Native and Modified Fucoidans from Brown Algae Fucus evanescens In Vitro and In Vivo.

The enzymatic depolymerization of fucoidans from brown algae allowed the production of their standardized derivatives with different biological activities. This work aimed to compare the antiviral activities of native (FeF) and modified with enzyme (FeHMP) fucoidans from F. evanescens. The cytotoxicity and antiviral activities of the FeF and FeHMP against herpes viruses (HSV-1, HSV-2), enterovirus (ECHO-1), and human immunodeficiency virus (HIV-1) in Vero and human MT-4 cell lines were examined by methylthiazolyltetrazolium bromide (MTT) and cytopathic effect (CPE) reduction assays, respectively. The efficacy of fucoidans in vivo was evaluated in the outbred mice model of vaginitis caused by HSV-2. We have shown that both FeF and FeHMP significantly inhibited virus-induced CPE in vitro and were more effective against HSV. FeF exhibited antiviral activity against HSV-2 with a selective index (SI) > 40, and FeHMP with SI ˃ 20, when they were added before virus infection or at the early stages of the HSV-2 lifecycle. Furthermore, in vivo studies showed that after intraperitoneal administration (10 mg/kg), both FeF and FeHMP protected mice from lethal intravaginal HSV-2 infection to approximately the same degree (44-56%). Thus, FeF and FeHMP have comparable potency against several DNA and RNA viruses, allowing us to consider the studied fucoidans as promising broad-spectrum antivirals.

Biologically active polyphenolic compounds from Lespedeza bicolor.

We investigated the ability of six prenylated prerocarpans, stilbenoid, and a new dimeric flavonoid, lespebicolin B, from stem bark as well as two 3-O-rutinosides and a mixture of 3-O-ß-D-glucosides of quercetin and kaempferol from flowers of Lespedeza bicolor to inhibit HSV-1 replication in Vero cells. Pretreatment of HSV-1 with polyphenolic compounds (direct virucidal effect) showed that pterocarpans lespedezol A2 (1), (6aR,11aR)-6a,11a-dihydrolespedezol A2 (2), (6aR,11aR)-2-isoprenyldihydrolespedezol A2 (4), and (6aR,11aR,3'R)-dihydrolespedezol A3 (5) significantly inhibited viral replication, with a selective index (SI) ≥10. Compound 4 possessed the lowest 50% - inhibiting concentration (IC50) and the highest SI values (2.6 µM and 27.9, respectively) in this test. (6aR,11aR)-2-Isoprenyldihydrolespedezol A2 (4) also had a moderate effect under simultaneous treatment of Vero cells with the tested compound and virus (IC50 and SI values were 5.86 µM and 12.4, respectively). 3-O-rutinosides of quercetin and kaempferol and a mixture of 3-O-ß-D-glucosides of quercetin and kaempferol (10 and 12) also showed significant virucidal activity, with SI values of 12.5, 14.6, and 98.2, respectively, and IC50 values of 8.6, 12.2, and 3.6, respectively. We also performed a quantitative structure-activity relationship (QSAR) analysis of data on the virucidal activity of polyphenolics with 4 < pIC50 < 6. It was found that the virucidal activity of these compounds depended on both the structure of the aromatic part and the conformation of geranyl and isoprenyl side chains of their molecules. These findings are correlated with the largest value of the principal moment of inertia (pmi) descriptor describing the geometry of molecules.

Molecular Mechanisms of Interaction Between Human Immune Cells and Far Eastern Tick-Borne Encephalitis Virus Strains.

Although studies have established that immune mechanisms are important in controlling tick-borne encephalitis virus (TBEV) infection, the interactions of different TBEV strains with cells of innate and adaptive immunity are not well understood. In this study, the ability of two Far Eastern subtype TBEV strains (Dal'negorsk and Primorye-183) with various degrees of pathogenicity for humans to modulate the expression of membrane molecules differently on human immune cells were investigated using a whole-blood flow cytometry-based assay. The whole-blood samples (from 10 healthy donors) were infected with TBEV strains and analyzed for the virus binding to the blood cells, as well as expression of adhesion (CD11b and ICAM-1) and activation (CD69, CD25, CD95) molecules on the surfaces of monocytes, granulocytes, natural killer (NK) cells, and T-lymphocytes (CD4+, CD8+) at selected times (3, 6, and 24 h post-infection). It was found that the highly pathogenic Dal'negorsk strain penetrated rapidly and was actively replicated in the blood cells, inducing downregulation of CD11b, ICAM-1, and CD69 on monocytes and a significant decrease of NK cells expressing CD69, CD25, CD95, and CD8 T-lymphocytes expressing CD69 compared with the mock-infected cells. The nonpathogenic Primorye-183 strain penetrated slowly and was replicated in the blood cells, but caused a significant increase in the adhesion and activation of molecule expression to trigger innate defense mechanisms and enable the rapid elimination of the virus from the organism. Thus, TBEV-induced activation or suppression of adhesion and activation receptors expression form an essential part of fundamental virus properties, that is, virulence and pathogenicity.