Strategies for Evaluation of Enveloped Virus Inactivation in Red Cell Concentrates Using Hypericin

Membrane-Targeting Perylenylethynylphenols Inactivate Medically Important Coronaviruses via the Singlet Oxygen Photogeneration Mechanism

Perylenylethynyl derivatives have been recognized as broad-spectrum antivirals that target the lipid envelope of enveloped viruses. In this study, we present novel perylenylethynylphenols that exhibit nanomolar or submicromolar antiviral activity against Severe Acute Respiratory Syndrome Coronavirus-2 (SARS-CoV-2) and feline infectious peritonitis virus (FIPV) in vitro. Perylenylethynylphenols incorporate into viral and cellular membranes and block the entry of the virus into the host cell. Furthermore, these compounds demonstrate an ability to generate singlet oxygen when exposed to visible light. The rate of singlet oxygen production is positively correlated with antiviral activity, confirming that the inhibition of fusion is primarily due to singlet-oxygen-induced damage to the viral envelope. The unique combination of a shape that affords affinity to the lipid bilayer and the capacity to generate singlet oxygen makes perylenylethynylphenols highly effective scaffolds against enveloped viruses. The anticoronaviral activity of perylenylethynylphenols is strictly light-dependent and disappears in the absence of daylight (under red light). Moreover, these compounds exhibit negligible cytotoxicity, highlighting their significant potential for further exploration of the precise antiviral mechanism and the broader scope and limitations of this compound class.

In vitro screening of anti-viral and virucidal effects against SARS-CoV-2 by Hypericum perforatum and Echinacea

Hypericum perforatum and Echinacea are reported to have antiviral activities against several viral infections. In this study, H. perforatum (St. John's Wort) and Echinacea were tested in vitro using Vero E6 cells for their anti-viral effects against the newly identified Severe Acute Respiratory Syndrome Coronavirus-2 (SARS-CoV-2) through its infectious cycle from 0 to 48 h post infection. The hypericin of H. perforatum and the different parts (roots, seeds, aerial) of two types of Echinacea species (Echinacea purpurea and Echinacea angustifolia) were tested for their anti-viral activities to measure the inhibition of viral load using quantitative real-time polymerase chain reaction (qRT-PCR) on cell culture assay. Interestingly, the H. perforatum-Echinacea mixture (1:1 ratio) of H. perforatum and Echinacea was tested as well on SARS-CoV-2 and showed crucial anti-viral activity competing H. perforatum then Echinacea effects as anti-viral treatment. Therefore, the results H. perforatum and Echinacea species, applied in this study showed significant anti-viral and virucidal effects in the following order of potency: H. perforatum, H. perforatum-Echinacea mixture, and Echinacea on SARS-CoV-2 infectious cycle. Additionally, molecular simulation analysis of the compounds with essential proteins (Mpro and RdRp) of the SARS-CoV-2 revealed the most potent bioactive compounds such as Echinacin, Echinacoside, Cyanin, Cyanidin 3-(6''-alonylglucoside, Quercetin-3-O-glucuronide, Proanthocyanidins, Rutin, Kaempferol-3-O-rutinoside, and Quercetin-3-O-xyloside. Thus, based on the outcome of this study, it is demanding the setup of clinical trial with specific therapeutic protocol.

Photodynamic viral inactivation: Recent advances and potential applications

Antibiotic-resistant bacteria, which are growing at a frightening rate worldwide, has put the world on a long-standing alert. The COVID-19 health crisis reinforced the pressing need to address a fast-developing pandemic. To mitigate these health emergencies and prevent economic collapse, cheap, practical, and easily applicable infection control techniques are essential worldwide. Application of light in the form of photodynamic action on microorganisms and viruses has been growing and is now successfully applied in several areas. The efficacy of this approach has been demonstrated in the fight against viruses, prompting additional efforts to advance the technique, including safety use protocols. In particular, its application to suppress respiratory tract infections and to provide decontamination of fluids, such as blood plasma and others, can become an inexpensive alternative strategy in the fight against viral and bacterial infections. Diverse early treatment methods based on photodynamic action enable an accelerated response to emerging threats prior to the availability of preventative drugs. In this review, we evaluate a vast number of photodynamic demonstrations and first-principle proofs carried out on viral control, revealing its potential and encouraging its rapid development toward safe clinical practice. This review highlights the main research trends and, as a futuristic exercise, anticipates potential situations where photodynamic treatment can provide a readily available solution.

The Biochemical and Genetic Basis for the Biosynthesis of Bioactive Compounds in Hypericum Perforatum L., One of the Largest Medicinal Crops in Europe

Hypericum perforatum L. commonly known as Saint John's Wort (SJW), is an important medicinal plant that has been used for more than 2000 years. Although H. perforatum produces several bioactive compounds, its importance is mainly linked to two molecules highly relevant for the pharmaceutical industry: the prenylated phloroglucinol hyperforin and the naphtodianthrone hypericin. The first functions as a natural antidepressant while the second is regarded as a powerful anticancer drug and as a useful compound for the treatment of Alzheimer's disease. While the antidepressant activity of SJW extracts motivate a multi-billion dollar industry around the world, the scientific interest centers around the biosynthetic pathways of hyperforin and hypericin and their medical applications. Here, we focus on what is known about these processes and evaluate the possibilities of combining state of the art omics, genome editing, and synthetic biology to unlock applications that would be of great value for the pharmaceutical and medical industries.

Antimicrobial Photoinactivation Approach Based on Natural Agents for Control of Bacteria Biofilms in Spacecraft

A spacecraft is a confined system that is inhabited by a changing microbial consortium, mostly originating from life-supporting devices, equipment collected in pre-flight conditions, and crewmembers. Continuous monitoring of the spacecraft’s bioburden employing culture-based and molecular methods has shown the prevalence of various taxa, with human skin-associated microorganisms making a substantial contribution to the spacecraft microbiome. Microorganisms in spacecraft can prosper not only in planktonic growth mode but can also form more resilient biofilms that pose a higher risk to crewmembers’ health and the material integrity of the spacecraft’s equipment. Moreover, bacterial biofilms in space conditions are characterized by faster formation and acquisition of resistance to chemical and physical effects than under the same conditions on Earth, making most decontamination methods unsafe. There is currently no reported method available to combat biofilm formation in space effectively and safely. However, antibacterial photodynamic inactivation based on natural photosensitizers, which is reviewed in this work, seems to be a promising method.

Trends and targets in antiviral phototherapy

Photodynamic therapy (PDT) is a well-established treatment option in the treatment of certain cancerous and pre-cancerous lesions. Though best-known for its application in tumor therapy, historically the photodynamic effect was first demonstrated against bacteria at the beginning of the 20^th century. Today, in light of spreading antibiotic resistance and the rise of new infections, this photodynamic inactivation (PDI) of microbes, such as bacteria, fungi, and viruses, is gaining considerable attention. This review focuses on the PDI of viruses as an alternative treatment in antiviral therapy, but also as a means of viral decontamination, covering mainly the literature of the last decade. The PDI of viruses shares the general action mechanism of photodynamic applications: the irradiation of a dye with light and the subsequent generation of reactive oxygen species (ROS) which are the effective phototoxic agents damaging virus targets by reacting with viral nucleic acids, lipids and proteins. Interestingly, a light-independent antiviral activity has also been found for some of these dyes. This review covers the compound classes employed in the PDI of viruses and their various areas of use. In the medical area, currently two fields stand out in which the PDI of viruses has found broader application: the purification of blood products and the treatment of human papilloma virus manifestations. However, the PDI of viruses has also found interest in such diverse areas as water and surface decontamination, and biosafety.

Recent Advances in Homogeneous Metal-Catalyzed Aerobic C–H Oxidation of Benzylic Compounds

Csp3–H oxidation of benzylic methylene compounds is an established strategy for the synthesis of aromatic ketones, esters, and amides. The need for more sustainable oxidizers has encouraged researchers to explore the use of molecular oxygen. In particular, homogeneous metal-catalyzed aerobic oxidation of benzylic methylenes has attracted much attention. This account summarizes the development of this oxidative strategy in the last two decades, examining key factors such as reaction yields, substrate:catalyst ratio, substrate scope, selectivity over other oxidation byproducts, and reaction conditions including solvents and temperature. Finally, several mechanistic proposals to explain the observed results will be discussed.

Thidiazuron-induced abnormalities in plant tissue cultures

Thidiazuron (TDZ) is a proven effective and potent synthetic plant growth regulator for organogenic, regeneration, and developmental pathways, including axillary and adventitious shoot proliferation, somatic embryogenesis, and in vitro flowering. TDZ has facilitated the establishment of in vitro cultures for several plant species, especially woody and recalcitrant plants, which has enabled their genetic transformation and improvement. Despite the effectiveness and advantages of using TDZ, several drawbacks are associated with its application in plant tissue culture. This review addresses the morphological, physiological, and cytogenetic abnormalities associated with the use of TDZ in vitro, and provides a summary of these abnormalities in several plant species.

Hypericin-Enhanced Argon Laser Photocoagulation for Subfoveal Choroidal Neovascular Membrane in Age-Related Macular Degeneration: A Pilot Study

Purpose

To evaluate the efficacy and safety of hypericin-enhanced argon laser photocoagulation (H-ALP) in the treatment of subfoveal choroidal neovascular membrane (CNM) secondary to age-related macular degeneration (ARMD).

Methods

After preliminary studies for definition of parameters, argon-green laser was administered 4 hours after single dose of oral 1800 mg hypericin (Saint-John's wort tablets, 0.3%, 300 mg) with a subthreshold light fluence, 24 J/cm2 in 34 eyes (20 with subfoveal classical and 14 with subfoveal occult CNM). Additionally, histopathologic examination was done in two eyes destined for enucleation and exenteration. Maintenance therapy (one tablet, twice a day) was performed for the following 6 months. Anatomic (complete closure of CNM) and functional success (improvement of final visual acuity in three or more Snellen lines) were analyzed with minimum 6-month follow-ups.

Results

Histopathologic examinations revealed photothrombosed choriocapillaries together with minimal retinal pigment epithelial disruption in H-ALP exposed areas. One to four (mean 1.88±0.91) treatment sessions were applied in 6 to 29 months (mean 12.2±5.1 months) follow-up period. Twenty-three (67.6%) eyes had 12 months follow-up. Two eyes in each group had functional success (20% in subfoveal classical and 14.3% in subfoveal occult CNM), which had a minimum 12-month follow-up. Anatomic success was achieved in 16 of 20 (80%) eyes with subfoveal classical and 10 of 14 (71.4%) eyes with subfoveal occult CNM. Severe gastric irritation was noted in 1 (2.9%) and pigment epithelial rupture in 2 (5.9%) patients.

Conclusions

H-ALP is a novel and low-cost treatment for subfoveal CNM secondary to ARMD. It seems its efficacy depends on the photodynamic and antiproliferative properties of hypericin. Comparative studies are required to apply this new technique in ophthalmic practice.

Hypericin in the Light and in the Dark: Two Sides of the Same Coin

Hypericin (4,5,7,4',5',7'-hexahydroxy-2,2'-dimethylnaphtodianthrone) is a naturally occurring chromophore found in some species of the genus Hypericum, especially Hypericum perforatum L. (St. John's wort), and in some basidiomycetes (Dermocybe spp.) or endophytic fungi (Thielavia subthermophila). In recent decades, hypericin has been intensively studied for its broad pharmacological spectrum. Among its antidepressant and light-dependent antiviral actions, hypericin is a powerful natural photosensitizer that is applicable in the photodynamic therapy (PDT) of various oncological diseases. As the accumulation of hypericin is significantly higher in neoplastic tissue than in normal tissue, it can be used in photodynamic diagnosis (PDD) as an effective fluorescence marker for tumor detection and visualization. In addition, light-activated hypericin acts as a strong pro-oxidant agent with antineoplastic and antiangiogenic properties, since it effectively induces the apoptosis, necrosis or autophagy of cancer cells. Moreover, a strong affinity of hypericin for necrotic tissue was discovered. Thus, hypericin and its radiolabeled derivatives have been recently investigated as potential biomarkers for the non-invasive targeting of tissue necrosis in numerous disorders, including solid tumors. On the other hand, several light-independent actions of hypericin have also been described, even though its effects in the dark have not been studied as intensively as those of photoactivated hypericin. Various experimental studies have revealed no cytotoxicity of hypericin in the dark; however, it can serve as a potential antimetastatic and antiangiogenic agent. On the contrary, hypericin can induce the expression of some ABC transporters, which are often associated with the multidrug resistance (MDR) of cancer cells. Moreover, the hypericin-mediated attenuation of the cytotoxicity of some chemotherapeutics was revealed. Therefore, hypericin might represent another St. John's wort metabolite that is potentially responsible for negative herb-drug interactions. The main aim of this review is to summarize the benefits of photoactivated and non-activated hypericin, mainly in preclinical and clinical applications, and to uncover the "dark side" of this secondary metabolite, focusing on MDR mechanisms.

Aerobic oxidation at benzylic positions catalyzed by a simple Pd(OAc)2/bis-triazole system

An extremely active palladium catalyst system for the aerobic oxidation of benzyl alcohols and benzylic C–H oxidation is described.

Synthesis of ketones via organolithium addition to acid chlorides using continuous flow chemistry

An efficient method for the synthesis of ketones using organolithium and acid chlorides under continuous flow conditions has been developed.

Continuous flow synthesis of ketones from carbon dioxide and organolithium or Grignard reagents

We describe an efficient continuous flow synthesis of ketones from CO2 and organolithium or Grignard reagents that exhibits significant advantages over conventional batch conditions in suppressing undesired symmetric ketone and tertiary alcohol byproducts. We observed an unprecedented solvent-dependence of the organolithium reactivity, the key factor in governing selectivity during the flow process. A facile, telescoped three-step-one-flow process for the preparation of ketones in a modular fashion through the in-line generation of organometallic reagents is also established.

Tetraethylammonium iodide catalyzed synthesis of diaryl ketones via the merger of cleavage of C–C double bonds and recombination of aromatic groups

An efficient method for synthesizing diaryl ketones via merging oxidative cleavage of C–C double bonds and recombination of aromatic groups is developed with Et₄NI (2.5 mol%) as the catalyst and NaIO₄ as the oxidant.

Pd-catalysed ortho-C-H Acylation/cross Coupling of 2-arylbenzo[d]thiazoles with Aldehydes Using tert-butyl Hydroperoxide as Oxidant

An efficient palladium-catalysed protocol for direct C–H bond acylation by cross coupling of 2-arylbenzo[d]thiazoles and aldehydes using tert-butyl hydroperoxide as the oxidant is reported. The process provides a useful method for the synthesis of aromatic ketones directly from aldehydes. In addition, the reaction can tolerate various functional groups in good yield with high regioselectivity.

Developing pathogen reduction technologies for RBC suspensions

Numerous studies have evaluated a wide variety of photosensitizers and alkylating agents as candidates for a pathogen reduction process to be used in RBC suspensions. The methodologies that produce robust inactivation of pathogens with maintenance of RBC properties during storage involve those that specifically target nucleic acids. This has been demonstrated through in vitro studies by flexible photosensitizers, which specifically target nucleic acid but do not engage in photochemistry when free in solution and nucleic acid alkylating agents in conjunction with extracellular quencher(s) to protect against RBC membrane alkylation. The flexible photosensitizer method must be scaled up to entire units, and toxicology studies would need to be performed for further development. Clinical trials will ultimately be necessary to further develop either flexible photosensitizers or nucleic acid alkylating methods with quenchers for use in Transfusion Medicine.

Characterization of a novel alphaherpesvirus associated with fatal infections of domestic rabbits

A virus was found to be associated with a severe disease affecting rabbits on a farm near Anchorage, Alaska. Extracts from the skin of infected rabbits produced syncytia and cell lysis in cultured rabbit skin, rabbit kidney, and Vero cells. Examination of the infectious agent by electron microscopy revealed an icosahedral nucleocapsid surrounded by an envelope with a diameter of about 120 nm, suggesting that it was a herpesvirus. The viral genome was determined to be composed of double-stranded DNA of 120-130 kbp. PCR using degenerate primers to conserved herpesvirus genes was used to amplify sequences from purified viral DNA. Sequencing of these products allowed the design of specific primers so that complete sequence data for a number of genes could be determined. Analysis of these data indicated that the virus is most closely related to bovine herpesvirus 2. The next most closely related viruses are human herpesviruses 1 and 2, and a number of cercopithecine herpesviruses. Experimental exposure of domestic rabbits to the isolate resulted in severe clinical disease and necrosis in the spleen and lymph node. In addition, viral DNA was identified in a variety of tissues by PCR, consistent with a systemic infection. Taken together, these data suggest that this virus is highly pathogenic for domestic rabbits and belongs to the family Herpesviridae, subfamily Alphaherpesvirinae, genus Simplexvirus.

Evaluation of the sensitivity of red blood cell markers to detect photodynamic membrane damage

BACKGROUND

Photodynamic dyes have been used to investigate pathogen reduction methods in RBC suspensions, but treatment with sensitizers and light can produce unwanted membrane damage during routine blood bank storage. This study compares the relative sensitivity of three assays for detecting RBC membrane damage.

STUDY DESIGN AND METHODS

RBCs were treated with dimethylmethylene blue and red light-emitting diode light under four conditions differing in photodynamic stringency and subsequently stored under refrigerated conditions for up to 42 days. Hemolysis, potassium release, and the apoptosis marker annexin V binding were assayed immediately after phototreatment and following storage.

RESULTS

In terms of increasing sensitivity for detecting photodynamic RBC membrane damage was enhanced ion leakage >> hemolysis > annexin V binding.

CONCLUSION

Although very stringent photodynamic treatment conditions generate annexin V-positive RBCs, the assay will not detect more subtle membrane damage that is readily detected by other well-established methods. In addition, many RBCs destined for photo-induced hemolysis later in storage are annexin V-negative throughout the storage period, suggesting that the two measures are not directly related.

Photodynamic effect of hypericin and a water-soluble derivative on isolated crayfish neuron and surrounding glial cells

Hypericin (Hyp) has been proposed as a fluorochrome for fluorescence diagnostics and as a photosensitizer for photodynamic therapy of cancer. However, its insolubility in water is a serious drawback. A novel water-soluble hypericin derivative (Hyp-S) has been constructed, using polyvinylpyrrolidone as a carrier. We used the crayfish stretch receptor, consisting of receptor neuron and satellite glial cells, for comparison of the photodynamic effects of Hyp and Hyp-S. Hyp-S was more toxic in the dark than Hyp and inactivated the neurons at concentrations exceeding 4 microM while Hyp was toxic to the neurons only at the concentrations larger than 20 microM. Electrophysiological investigations revealed polyphasic neuron responses to photosensitization with Hyp as well as with Hyp-S (1 microM concentration, 30 min incubation; irradiation with filtered light from a lamp with an emission maximum near 600 nm and an intensity of 0.2 W/cm2). In the concentration range 1-4 microM Hyp-S was more phototoxic than Hyp. Fluorescence microscopy showed that both sensitizers were predominately localized in the glial envelope surrounding the neuron. A minor fraction of hypericin was found in the neuron perinuclear area rich in cytoplasm organelles. This suggests the potential application of Hyp and Hyp-S for visualization and selective photodynamic treatment of malignant gliomas.

[Methyl-D3]2hypericin as internal standard for quantification in human plasma

The multistep synthesis and negative ion-ESI fragmentation pattern of [methyl-D(3)](2)hypericin (1-D(6)) is described. The application of 1-d(6) as internal standard for the quantification of hypericin (1) in the ng mL(-1) range in human plasma by isotope-dilution LC-MS is demonstrated. The hypericin-containing plasma samples are spiked with 1-D(6), deproteinized and extracted with ethyl acetate. The extracts are injected into a HPLC-ESI-ion-trap system and the mass-separated negative ions from 1 and 1-D(6) are analysed. From their intensities linear standard curves over the concentration range from 1 to 10 ng mL(-1) are obtained. Accuracy, precision and recovery are discussed.

Chemical and photochemical electron transfer of new helianthrone derivatives: aspects of their photodynamic activity

Helianthrones 2-4 are a new class of synthetic photosensitizers, which have a molecular skeleton related to that of hypericin. We established that irradiation of heliantrones with visible light leads to the formation of semiquinone radicals and reactive oxygen species. The structures of the paramagnetic anion species produced by electron transfer were calculated on the density functional level and investigated by cyclovoltammetry, UV/vis, and EPR/ENDOR spectroscopy. As with hypericin, the pi system of the helianthrones was found to be considerably deviated from planarity, and, upon electron transfer, deprotonation in the bay region occurs. The structure of the semiquinone radicals was found to be identical in THF, DMF, and aqueous buffered solutions regardless of the means by which reduction was achieved. Semiquinone radicals can be formed via self-electron transfer between the excited state and the ground state or via electron transfer from an electron donor to the excited state of helianthrone. Therefore, the presence of an electron donor significantly enhanced the photogeneration of semiquinone and superoxide radical. The kinetic studies showed that no significant photochemical destruction of helianthrones occurred upon irradiation. Generation of superoxide and singlet oxygen upon irradiation of helianthrones was established by spin trapping techniques. This shows that both type I and type II mechanisms are of importance for the photodynamic action of these compounds.

Quinacrine enhances vesicular stomatitis virus inactivation and diminishes hemolysis of dimethylmethylene blue-phototreated red cells

Several photodynamic methods for virus inactivation in red blood cell (RBC) suspensions have resulted in unwanted hemolysis during extended 1-6 degrees C storage. To explore the possibility that hemolysis may be mediated by a membrane-bound dye, a molecule similar in structure to yet different in light absorption properties from the photosensitizer was used as an inhibitor for RBC membrane binding in virus photoinactivation and photohemolysis studies. The addition of 500 pM quinacrine to oxygenated RBC before treatment with 3.6 microM dimethylmethylene blue (DMMB) and 219 mJ/cm2 red light resulted in an increased extracellular concentration of the sensitizer, increased extracelluar viral inactivation kinetics, and decreased hemolysis during 1-6 degrees C storage without alteration of quinacrine absorption properties. These results collectively suggest that despite its recognized affinity for viral nucleic acid, DMMB also binds to RBC membranes and that the bound dye is, in part, responsible for photoinduced hemolysis.

Quasispecies in the 5' untranslated genomic region of bovine viral diarrhoea virus from a single individual

The variability of the 5' untranslated genomic region (5'UTR) of bovine viral diarrhoea virus (BVDV) RNA obtained from a single individual was analysed. Lung, kidney and spleen tissues from a naturally infected foetus were used as the source of viral RNA. A fragment of 288 bases of the internal ribosome entry site from the BVDV 5'UTR was amplified by RT-PCR using a proofreading DNA polymerase. PCR products were cloned into pGem and, subsequently, transformed into Escherichia coli. The single-strand conformational polymorphisms of 158 lung-derived clones were analysed; a total of 11 banding patterns was observed. DNAs corresponding to all patterns were sequenced. Of the randomly selected clones, 11 and 10 clones derived from the kidney and spleen, respectively, were also sequenced. All sequences presented differences ranging from 1 to 6 nt substitutions. Analysis of the secondary structure of the variant sequences and comparisons to variant nucleotide sites from the 5'UTR of several BVDV isolates showed that the observed changes were almost free of randomness. Clustering and phylogenetic analyses suggested the existence of low-kinetic variants. BVDV quasispecies may be involved in establishing persistent infections by means of eluding maternal antibodies. The methods described here may be adapted easily both to analyse large numbers of samples from other genomic regions and for the study of BVDV quasispecies evolution in other systems.

Hypericin in cancer treatment: more light on the way

Photodynamic therapy (PDT) has been described as a promising new modality for the treatment of cancer. PDT involves the combination of a photosensitizing agent (photosensitizer), which is preferentially taken up and retained by tumor cells, and visible light of a wavelength matching the absorption spectrum of the drug. Each of these factors is harmless by itself, but when combined they ultimately produce, in the presence of oxygen, cytotoxic products that cause irreversible cellular damage and tumor destruction. Hypericin, a powerful naturally occurring photosensitizer, is found in Hypericum perforatum plants, commonly known as St. John's wort. In recent years increased interest in hypericin as a potential clinical anticancer agent has arisen since several studies established its powerful in vivo and in vitro antineoplastic activity upon irradiation. Investigations of the molecular mechanisms underlying hypericin photocytotoxicity in cancer cells have revealed that this photosensitizer can induce both apoptosis and necrosis in a concentration and light dose-dependent fashion. Moreover, PDT with hypericin results in the activation of multiple pathways that can either promote or counteract the cell death program. This review focuses on the more recent advances in the use of hypericin as a photodynamic agent and discusses the current knowledge on the signaling pathways underlying its photocytotoxic action.

The structure of hypericin in solution. Searching for hypericin's 1,6 tautomer

Hypericin in organic solvents displays two types of electronic spectra: one type which shows a distinct solvatochromic effect, the stable form, and the other, the unstable form, which lacks this property. The latter type is formed in dry nonprotic solvents (e.g. tetrahydrofuran, EtOAc) and can be converted to the stable form on addition of protic solvents. In order to establish the tautomeric structure of the unstable form we applied conventional nuclear magnetic resonance techniques as well as two-dimensional gradient-enhanced heteronuclear multiple-quantum correlation, gradient-enhanced ROESY and one-dimensional nuclear Overhauser effect difference experiments. All these techniques pointed to the fact that the unstable form has the 7,14-diketo tautomeric structure, like the stable form, and not the 1,6-diketo structure. Electronic spectroscopy indicated that the unstable form has acidic properties and therefore possesses two free OH groups at C3 and C4 at the bay region of the molecule.

Hypericin derivatives: substituent effects on radical-anion formation

The electron-transfer properties of the hypericin derivatives, dibromo-, hexaacetyl-, hexamethyl- and desmethylhypericin, were studied. Cyclovoltammetric measurements revealed that dibromo- and desmethylhypericin have almost the same redox potentials as the parent hypericin. Substitution of the hydroxyl groups by acetoxy leads to less negative E1/2 values, whereas methoxy substitution induces more negative values. Electron paramagnetic resonance (EPR)/electron nuclear double resonance/general TRIPLE spectroscopy and quantum mechanical calculations were used to establish the structure of the one-electron reduced stages of hypericin derivatives. Proton loss in the bay region, already demonstrated for hypericin, was also found for dibromo- and desmethylhypericin. The spin and charge of the radical ions are predominately confined to the central biphenoquinone moiety of the hypericin skeleton. Generation of the radical ions by in situ electrolysis indicates that the redox potentials of hypericin, dibromo- and desmethylhypericin, containing hydroxyls at the 1, 3, 4, 6, 8 and 13 positions, largely depend on the solvent. With phosphate-buffered saline (pH 7.4)/dimethylsulfoxide (DMSO) as the solvent the EPR spectra of the corresponding radical ions appear at markedly lower potentials than in pure DMSO and N,N'-dimethylformamide. However, this effect is not observable for hexaacetyl- and hexamethyl-hypericin-lacking hydroxyl groups. In all cases the EPR data and calculations revealed the presence of 7,14 tautomers.

Pharmacokinetics, safety, and antiviral effects of hypericin, a derivative of St. John's wort plant, in patients with chronic hepatitis C virus infection

Hypericin is a natural derivative of the common St. Johns wort plant, Hypericum perforatum. It has in vitro activity against several viruses, including bovine diarrhea virus, a pestivirus with structural similarities to hepatitis C virus (HCV). We conducted a phase I dose escalation study to determine the safety and antiviral activity of hypericin in patients with chronic HCV infection. The first 12 patients received an 8-week course of 0.05 mg of hypericin per kg of body weight orally once a day; 7 patients received an 8-week course of 0.10 mg/kg orally once a day. At the end of the 8-week period of treatment, no subject had a change of plasma HCV RNA level of more than 1.0 log(10). Five of 12 subjects receiving the 0.05-mg/kg/day dosing schedule and 6 of 7 subjects receiving the 0.10-mg/kg/day dosing schedule developed phototoxic reactions. No other serious adverse events associated with hypericin use occurred. The pharmacokinetic data revealed a long elimination half-life (mean values of 36.1 and 33.8 h, respectively, for the doses of 0.05 and 0.1 mg/kg) and mean area under the curve determinations of 1.5 and 3.1 microg/ml x hr, respectively. In sum, hypericin given orally in doses of 0.05 and 0.10 mg/kg/d caused considerable phototoxicity and had no detectable anti-HCV activity in patients with chronic HCV infection.