Detection of the antiviral activity of epicatechin isolated from Salacia crassifolia (Celastraceae) against Mayaro virus based on protein C homology modelling and virtual screening.

Mayaro fever, caused by Mayaro virus (MAYV) is a sub-lethal disease with symptoms that are easily confused with those of dengue fever, except for polyarthralgia, which may culminate in physical incapacitation. Recently, outbreaks of MAYV have been documented in metropolitan areas, and to date, there is no therapy or vaccine available. Moreover, there is no information regarding the three-dimensional structure of the viral proteins of MAYV, which is important in the search for antivirals. In this work, we constructed a three-dimensional model of protein C of MAYV by homology modelling, and this was employed in a manner similar to that of receptors in virtual screening studies to evaluate 590 molecules as prospective antiviral agents. In vitro bioassays were utilized to confirm the potential antiviral activity of the flavonoid epicatechin isolated from Salacia crassifolia (Celastraceae). The virtual screening showed that six flavonoids were promising ligands for protein C. The bioassays showed potent antiviral action of epicatechin, which protected the cells from almost all of the effects of viral infection. An effective concentration (EC50) of 0.247 µmol/mL was observed with a selectivity index (SI) of 7. The cytotoxicity assay showed that epicatechin has low toxicity, with a 50% cytotoxic concentration (CC50) greater than 1.723 µmol/mL. Epicatechin was found to be twice as potent as the reference antiviral ribavirin. Furthermore, a replication kinetics assay showed a strong inhibitory effect of epicatechin on MAYV growth, with a reduction of at least four logs in virus production. Our results indicate that epicatechin is a promising candidate for further testing as an antiviral agent against Mayaro virus and other alphaviruses.

Antiviral activity of Distictella elongata (Vahl) Urb. (Bignoniaceae), a potentially useful source of anti-dengue drugs from the state of Minas Gerais, Brazil.

AIMS: To investigate the in vitro antiviral activity of Distictella elongata (Vahl) Urb. ethanol extracts from leaves (LEE), fruits (FEE), stems and their main components. METHODS AND RESULTS: The antiviral activity was evaluated against human herpesvirus type 1 (HSV-1), murine encephalomyocarditis virus (EMCV), vaccinia virus Western Reserve (VACV-WR) and dengue virus 2 (DENV-2) by the 3-(4, 5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) colorimetric assay. LEE presented anti-HSV-1 [EC(50) 142.8 ± 5.3 µg ml(-1); selectivity index (SI) 2.0] and anti-DENV-2 activity (EC(50) 9.8 ± 1.3 µg ml(-1) ; SI 1.5). The pectolinarin (1) isolated from LEE was less active against HSV-1 and DENV-2. A mixture of the triterpenoids ursolic, pomolic and oleanolic acids was also obtained. Ursolic and oleanolic acids have shown antiviral activity against HSV-1. A mixture of pectolinarin (1) and acacetin-7-O-rutinoside (2) was isolated from FEE and has presented anti-DENV-2 activity (EC(50) 11.1 ± 1.6 µg ml(-1) ; SI > 45). Besides the antiviral activity, D. elongata has disclosed antioxidant effect. CONCLUSIONS: These data shows that D. elongata has antiviral activity mainly against HSV-1 and DENV-2, besides antioxidant activity. These effects might be principally attributed to flavonoids isolated. SIGNIFICANCE AND IMPACT OF THE STUDY: Distictella elongata might be considered a promising source of anti-dengue fever phytochemicals.

Antiviral activity of Bignoniaceae species occurring in the State of Minas Gerais (Brazil): part 1.

AIMS: To evaluate the antiviral activity of Bignoniaceae species occurring in the state of Minas Gerais, Brazil. METHODS AND RESULTS: Ethanol extracts of different anatomical parts of bignoniaceous plant species have been evaluated in vitro against human herpesvirus type 1 (HSV-1), vaccinia virus (VACV) and murine encephalomyocarditis virus (EMCV) by the 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide assay. A total of 34 extracts from 18 plant species selected according to ethnopharmacological and taxonomic criteria were screened. Fifteen of the 34 extracts (44.1%) have disclosed antiviral activity against one or more of the viruses assayed with EC(50) values in the range of 23.2 ± 2.5-422.7 ± 10.9 µg ml(-1). CONCLUSIONS: Twelve of the 34 extracts (35.3%) might be considered promising sources of antiviral natural products, as they have shown EC50 ≤ 100 µg ml(-1). The present screening discloses the high potential of the Bignoniaceae family as source of antiviral agents. SIGNIFICANCE AND IMPACT OF THE STUDY: Active extracts were identified and deserve bioguided studies for the isolation of antiviral compounds and studies on mechanism of action.

Box-Behnken design: an alternative for the optimization of analytical methods.

The present paper describes fundamentals, advantages and limitations of the Box-Behnken design (BBD) for the optimization of analytical methods. It establishes also a comparison between this design and composite central, three-level full factorial and Doehlert designs. A detailed study on factors and responses involved during the optimization of analytical systems is also presented. Functions developed for calculation of multiple responses are discussed, including the desirability function, which was proposed by Derringer and Suich in 1980. Concept and evaluation of robustness of analytical methods are also discussed. Finally, descriptions of applications of this technique for optimization of analytical methods are presented.