Mangiferin: A promising natural xanthone from Mangifera indica for the control of acyclovir - resistant herpes simplex virus 1 infection.

Mangiferin is found in many plant species as the mango tree (Mangifera indica) with ethnopharmacological applications and scientific evidence. The emergence of resistant herpes simplex virus (HSV) strains to Acyclovir (ACV) has encouraged the search for new drugs. We investigated the in vitro and in vivo activity of mangiferin obtained from M. indica against ACV-resistant HSV-1 (AR-29) and sensitive (KOS) strains. The in vitro activity was performed under varying treatment protocols. The substance showed a CC50 > 500 µg/mL and IC50 of 2.9 µg/mL and 3.5 µg/mL, respectively, for the AR-29 and KOS strains. The in vivo activity was performed in Balb/c mice treated with 0.7% topical mangiferin formulation. This formulation inhibited most effectively the AR-29 strain, attenuated the lesions, postponed their appearance or enhanced healing, in comparison to control group. We demonstrated the potentiality of mangiferin from M. indica to control HSV replication with emphasis to ACV-resistant infection.

Co-encapsulation of acyclovir and curcumin into microparticles improves the physicochemical characteristics and potentiates in vitro antiviral action: Influence of the polymeric composition.

The present study developed and characterized microparticles formulations containing acyclovir and curcumin co-encapsulated in order to overcome the biopharmaceutical limitations and increase the antiviral effect of both drugs. The microparticles were prepared by a spray drying methodology following the ratio 1:3 (drug:polymer), which were made by hydroxypropylmethylcellulose (HPMC) and/or Eudragit® RS100 (EUD). The MP-1 formulation was composed of HPMC and EUD (1:1), MP-2 formulation was composed only of HPMC and MP-3 formulation was composed only of EUD. All formulations showed yielding around 50% and acceptable powder flowability. Drug content determination around 82.1-96.8% and 81.8-87% for acyclovir and curcumin, respectively. The microparticles had spherical shape, size within 11.5-15.3 µm, unimodal distribution and no chemical interactions among the components of the formulations. Of particular importance, the polymeric composition considerably influenced on the release profile of the drugs. The in vitro release experiment demonstrated that the microencapsulation provided a sustained release of acyclovir as well as increased the solubility of curcumin. Besides, mathematical modeling indicated that the experimental fit biexponential equation. Importantly, drugs microencapsulation promoted superior antiviral effect against BoVH-1 virus in comparison to their free form, which could be attributed to the improvement in the aforementioned physicochemical parameters. Therefore, these formulations could be promising technological drug carriers for acyclovir and curcumin, which highlight the great offering a potential alternative treatment for viral herpes.

Ball-milled solid dispersions of BCS Class IV drugs: Impact on the dissolution rate and intestinal permeability of acyclovir.

Acyclovir, an analog of 2'-deoxyguanosine, is one of the most important drugs in the current approved antiviral treatment. However, it's biopharmaceutical properties, contribute to acyclovir's poor oral bioavailability, which restricts the clinical use of the drug. In this view, the aim of this work was to improve the dissolution rate and intestinal permeability of acyclovir through the development of ball milling solid dispersions with the hydrophilic carriers Pluronic F68®, hydroxypropylmethyl cellulose K100M® and chitosan. Solid dispersions were obtained and completely characterized through different solid state techniques. The solid state data demonstrated a decrease in the crystallinity (amorphous phase and defects) and the presence of hydrogen bonds for SD HPMC and SD CTS. The enhancement of dissolution rates was observed for all SDs developed. In addition, no detrimental effects over the in vitro antiviral activity were detected. The solid dispersions with Pluronic F68® significantly improved the intestinal permeability of acyclovir across Caco-2 cells. In summary, the SDs developed in this study could be considered as potential systems for solid dosage forms containing acyclovir with superior biopharmaceutical properties.

Stability of valacyclovir: implications for its oral bioavailability.

The absolute bioavailability of the prodrug valacyclovir, the l-valyl ester of acyclovir, after oral administration is approximately 54.5%. Since premature hydrolysis of this prodrug in the intestinal lumen may be a possible reason for its incomplete bioavailability and the chemical and enzymatic stability of the valacyclovir has been investigated. Release rates were investigated in both phosphate buffers with varying pH as well as in human and dog gastrointestinal fluids. The stability of the prodrug was found to be dependent on pH. This prodrug is chemically stable along the acidic pH side (under 4), while the prodrug degrades in alkaline medium through a base-catalyzed pseudo-first-order kinetics. The degradation of the prodrug valacyclovir progressed faster in intestinal fluid than in phosphate buffer at the same pH. There was no appreciable release of valacyclovir neither in the human and dog stomach contents nor in phosphate buffers at pHs fewer than 4, although its degradation was fastest in the human and dog stomach contents. In light of this result, we can conclude that the degradation of the valacyclovir in the upper intestinal lumen is probably one of the causes of its poor bioavailability.

Crystal structure of human purine nucleoside phosphorylase complexed with acyclovir.

In human, purine nucleoside phosphorylase (HsPNP) is responsible for degradation of deoxyguanosine and genetic deficiency of this enzyme leads to profound T-cell mediated immunosuppression. PNP is therefore a target for inhibitor development aiming at T-cell immune response modulation and has been submitted to extensive structure-based drug design. This work reports the first crystallographic study of human PNP complexed with acyclovir (HsPNP:Acy). Acyclovir is a potent clinically useful inhibitor of replicant herpes simplex virus that also inhibits human PNP but with a relatively lower inhibitory activity (K(i)=90 microM). Analysis of the structural differences among the HsPNP:Acy complex, PNP apoenzyme, and HsPNP:Immucillin-H provides explanation for inhibitor binding, refines the purine-binding site, and can be used for future inhibitor design.

Comparison of the antiviral activity and toxicity of a protein magnesium ammonium phospholinoleate anhydride polymer with other antiviral drugs.

1. SB-73, a magnesium ammonium phospholinoleate anhydride aggregate, exhibited antiviral action in vitro in the concentration range of 50 to 100 micrograms/ml against herpes simplex type 1, stomatitis vesicular virus, adenovirus type 5, and in vivo in the dose range of 0.7 to 1.3 mg/kg against canine parvovirus and distemper virus. 2. The lethal dose (LD50) was 2.71 +/- 1.55 g/kg body weight in mice inoculated intraperitoneally. Oral ingestion of the aggregate up to 30 g/kg body weight by mice had no lethal effects during the 14 days of observation. 3. In in vitro cytotoxicity experiments with fibroblasts (V-79 Chinese hamster cell line), no toxic effects were observed with SB-73 concentrations (120 micrograms/ml) having antiviral activity. 4. In a cellular proliferation experiment using hamster V-79 cells, we observed 72% proliferation after treatment of the cells with a high concentration (500 micrograms/ml) of SB-73. 5. Compound SB-73 showed no genotoxicity for human lymphocytes at concentrations of 100 micrograms/ml. 6. When the cytotoxicity and genotoxicity of SB-73 were compared with those of acyclovir, idoxuridine and AZT at 500 micrograms/ml concentrations the compound was found to have effects similar to those of acyclovir.

Comparison of the antiviral activity and toxicity of a protein magnesium ammonium phospholinoleate anhydride polymer with other antiviral drugs

1. SB-73, a magnesium ammonium phospholinoleate anhydride aggregate, exhibited antiviral action in vitro in the concentration range of 50 to 100 µg/ml against herpes simplex type 1, stomatitis vesicular virus, adenovirus type 5, and in vivo in the dose range of 0.7 to 1.3 mg/Kg against canine parvovirus distemper virus. 2. The lethal dose (LD50) was 2.71 ñ 1.55 g/Kg body weight in mice inoculated intraperitoneally. Oral ingestion of the aggregate up to 30 g/Kg body weight by mice had no lethal effects during the 14 days of observation. 3. In in vitro cytotoxicity experiments with fibroblasts (V-79 Chinese hamster cell line), no toxic effects were observed with SB-73 concentrations (120 µg/ml) having antiviral activity. 4. In a cellular proliferation experimental using hamster V-79 cells, we observed 72% proliferation after treatment of the cells with a high concentration (500 µg/ml) of SB-73. 5. Compound SB-73 showed no genotoxicity for human lymphocytes at concentrations of 100 µg/ml. 6. When the cytoxicity and genotoxicity of SB-73 wee compared with those of acyclovir, idoxuridine and AZT at 500µg/ml concentration the compound was found to have effects similar to those of acyclovir