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.

Influence of the Structural Features of Carrageenans from Red Algae of the Far Eastern Seas on Their Antiviral Properties.

The structural diversity and unique physicochemical properties of sulphated polysaccharides of red algae carrageenans (CRGs), to a great extent, determine the wide range of their antiviral properties. This work aimed to compare the antiviral activities of different structural types of CRGs: against herpes simplex virus type 1 (HSV-1) and enterovirus (ECHO-1). We found that CRGs significantly increased the resistance of Vero cells to virus infection (preventive effect), directly affected virus particles (virucidal effect), inhibited the attachment and penetration of virus to cells, and were more effective against HSV-1. CRG1 showed the highest virucidal effect on HSV-1 particles with a selective index (SI) of 100. CRG2 exhibited the highest antiviral activity by inhibiting HSV-1 and ECHO-1 plaque formation, with a SI of 110 and 59, respectively, when it was added before virus infection. CRG2 also significantly reduced the attachment of HSV-1 and ECHO-1 to cells compared to other CRGs. It was shown by molecular docking that tetrasaccharides-CRGs are able to bind with the HSV-1 surface glycoprotein, gD, to prevent virus-cell interactions. The revealed differences in the effect of CRGs on different stages of the lifecycle of the viruses are apparently related to the structural features of the investigated compounds.

Antiherpetic Activity of Carrageenan Complex with Echinochrome A and Its Liposomal Form.

Herpes simplex virus (HSV) infections, the incidence of which is still widespread throughout the world, are actualizing the search and development of new, more effective antiherpetic drugs. The development of multifunctional drug delivery systems, including liposome-based ones, has become a relevant and attractive concept in nanotechnology. The ability of complexes of κ- and Σ-carrageenans (CRGs)-sulfated polysaccharides of red algae, with echinochrome A (Ech), as well as the liposomal form of the Σ-CRG/Ech complex-to inhibit different stages of HSV-1 infection in Vero cells was studied. By quantum chemical calculations, it was shown that CRG forms stable complexes with Ech. We have shown that complexes of κ-CRG/Ech and Σ-CRG/Ech exhibit highest virucidal activity with a selectivity index (SI) of 270 and 350, respectively, and inhibition of virus-cell interaction (SI of 83 and 32, respectively). The liposomal form of the Σ-CRG/Ech complex after virus adsorption and penetration to cells effectively reduced the HSV-1 plaque formation. The virus-inhibiting activity of the liposomal form of the Σ-CRG/Ech complex was three times higher than that of the Σ-CRG/Ech complex itself. Obtaining CRGs/Ech complexes and their liposomal forms can become the basis of a successful strategy for the development of promising antiherpetic drugs.

In Vitro Anti-Orthohantavirus Activity of the High-and Low-Molecular-Weight Fractions of Fucoidan from the Brown Alga Fucus evanescens.

The Hantaan orthohantavirus (genovariant Amur-AMRV) is a rodent-borne zoonotic virus; it is the causative agent of haemorrhagic fever with renal syndrome in humans. The currently limited therapeutic options require the development of effective anti-orthohantavirus drugs. The ability of native fucoidan from Fucus evanescens (FeF) and its enzymatically prepared high-molecular-weight (FeHMP) and low-molecular-weight (FeLMP) fractions to inhibit different stages of AMRV infection in Vero cells was studied. The structures of derivatives obtained were determined using nuclear magnetic resonance (NMR) spectroscopy. We found that fucoidan and its derivatives exhibited significant antiviral activity by affecting the early stages of the AMRV lifecycle, notably virus attachment and penetration. The FeHMP and FeLMP fractions showed the highest anti-adsorption activity by inhibiting AMRV focus formation, with a selective index (SI) > 110; FeF had an SI of ~70. The FeLMP fraction showed a greater virucidal effect compared with FeF and the FeHMP fraction. It was shown by molecular docking that 2O-sulphated fucotetrasaccharide, a main component of the FeLMP fraction, is able to bind with the AMRV envelope glycoproteins Gn/Gc and with integrin ß3 to prevent virus-cell interactions. The relatively small size of these sites of interactions explains the higher anti-AMRV activity of the FeLMP fraction.

Antiviral Potential of Sea Urchin Aminated Spinochromes against Herpes Simplex Virus Type 1.

Herpes simplex virus type 1 (HSV-1) is one of the most prevalent pathogens worldwide requiring the search for new candidates for the creation of antiherpetic drugs. The ability of sea urchin spinochromes-echinochrome A (EchA) and its aminated analogues, echinamines A (EamA) and B (EamB)-to inhibit different stages of HSV-1 infection in Vero cells and to reduce the virus-induced production of reactive oxygen species (ROS) was studied. We found that spinochromes exhibited maximum antiviral activity when HSV-1 was pretreated with these compounds, which indicated the direct effect of spinochromes on HSV-1 particles. EamB and EamA both showed the highest virucidal activity by inhibiting the HSV-1 plaque formation, with a selectivity index (SI) of 80.6 and 50.3, respectively, and a reduction in HSV-1 attachment to cells (SI of 8.5 and 5.8, respectively). EamA and EamB considerably suppressed the early induction of ROS due to the virus infection. The ability of the tested compounds to directly bind to the surface glycoprotein, gD, of HSV-1 was established in silico. The dock score of EchA, EamA, and EamB was -4.75, -5.09, and -5.19 kcal/mol, respectively, which correlated with the SI of the virucidal action of these compounds and explained their ability to suppress the attachment and penetration of the virus into the 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.

Antiviral and Antioxidant Properties of Echinochrome A.

The aim of this study was to examine the in vitro antioxidant and antiviral activities of echinochrome A and echinochrome-based antioxidant composition against tick-borne encephalitis virus (TBEV) and herpes simplex virus type 1 (HSV-1). The antioxidant composition, which is a mixture of echinochrome A, ascorbic acid, and α-tocopherol (5:5:1), showed higher antioxidant and antiviral effects than echinochrome A. We suppose that echinochrome A and its composition can both directly affect virus particles and indirectly enhance antioxidant defense mechanisms in the hosting cell. The obtained results allow considering the echinochrome A and the composition of antioxidants on its basis as the promising agents with the both antioxidant and antiviral activities.

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.

Hemorrhagic Fever With Renal Syndrome in Vladivostok City, Russia.

Hemorrhagic fever with renal syndrome (HFRS) is a public health problem in Vladivostok city, Russia. From 1997 to 2019, a study of hantaviruses in Norway rats (Rattus norvegicus), a natural reservoir of Seoul virus (SEOV), and in HFRS patients was conducted. We demonstrated the presence of SEOV in the local population of Norway rats and detected SEOV in 10, Amur virus (AMRV) in 4 and Hantaan virus (HTNV) in 1 out of 15 HFRS patients. Genetic analysis based on partial S, M and L segment sequences revealed that the Russian SEOV strains were related most closely to strains from Cambodia and Vietnam. We postulate that the SEOV strains found in the port city of Vladivostok have been spread from South-East Asia as a result of distribution of rats during standard shipping trade activities. Moreover, we suggest that city residents may have acquired AMRV and HTNV infection during visits to rural areas.