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.

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.

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.