Antiviral effect and mode of action of methanolic extract of Verbascum thapsus L. on pseudorabies virus (strain RC/79).

The methanolic extract of Verbascum thapsus was evaluated for its antiviral activity against the pseudorabies virus strain RC/79 (PrV), and also for its cytotoxic activity on Vero cells. The extract showed CC50 values of 1100 µg mL⁻¹ and 1426 µg mL⁻¹ by NRU and MTT assays, respectively. The 50% inhibitory concentration of the extract for PrV plaque formation was determined at 35 µg mL⁻¹, and selectivity indices were 31.4 (NRU) and 40.7 (MTT). When cells were pre-treated with the extract prior to virus infection, the inhibition in plaque formation was 70%. PrV was highly inhibited when it was incubated with plant extract or when the extract was added during the adsorption phase (99%). However, no inhibitory effect was observed when the extract was added to the cells after the adsorption period. Thus, these results suggest that the methanolic extract of Verbascum thapsus may contain bioactive compound(s) that affect PrV mostly in the adsorption phase.

Evaluation of antiviral activity of aqueous extracts from Achyrocline satureioides against Western equine encephalitis virus.

Achyrocline satureioides (Asteraceae) is a medicinal plant traditionally used in Argentina for the treatment of intestinal infections and various digestive disorders. Its infusion is widely utilised for respiratory problems and viral infections. The objective of this study was to investigate cytotoxicity, virucidal and antiviral properties of the cold aqueous extract (CAE) and hot aqueous extract (HAE) of this plant against Western equine encephalitis virus (WEEV). Cytotoxicity in Vero cells was evaluated by maximum non-cytotoxic concentration (MNCC), neutral red (NR) uptake and MTT reduction methods. To study the antiviral activity of aqueous extracts, plaque reduction assay was performed after pre-treatment of host cells, adsorption, penetration and post-penetration of the virus. Extracellular virus inactivation was also analysed by the same method. Extracts showed strong inhibitory activity after virus penetration with selective index values of 32 (NR) and 63.3 (MTT) for the CAE, and 16.2 (NR) and 24.3 (MTT) for the HAE. Both extracts exhibited virucidal action with lower efficacy than their antiviral properties. The present results demonstrate that aqueous extracts of A. satureioides are active against WEEV. Further studies are needed in order to identify which compounds could be responsible for this effect, and how they exert antiviral action.

Antibacterial Efficacy of Dihydroxylated Chalcones in Binary and Ternary Combinations with Nalidixic Acid and Nalidix Acid-Rutin Against Escherichia coli ATCC 25 922.

In order to determine the existence of synergism, the bacteriostatic action of flavonoids against Escherichia coli ATCC 25 922 between dihydroxylated chalcones and a clinically interesting conventional antibiotic, binary combinations of 2',3-dihydroxychalcone, 2',4-dihydroxychalcone and 2',4'-dihydroxychalcone with nalidixic acid and its ternary combinations with rutin (inactive flavonoid) were assayed against this Gram negative bacterium. Using a kinetic-turbidimetric method, growth kinetics were monitored in broths containing variable amounts of dihydroxychalcone alone, combinations of dihydroxychalcone variable concentration-nalidixic acid constant concentration and dihydroxychalcone variable concentration-nalidixic acid constant concentration-rutin constant concentration, respectively. The minimum inhibitory concentrations of dihydroxychalcones alone and its binary and ternary combinations were evaluated. All chalcones, and their binary and ternary combinations showed antibacterial activity, being rutin an excellent synergizing for the dihydroxychalcone-nalidixic acid binary combination against E. coli ATCC 25 922. Thus, this synergistic effect is an important way that could lead to the development of new combination antibiotics against infections caused by E. coli.

Genotoxic evaluation of a methanolic extract of Verbascum thapsus using micronucleus test in mouse bone marrow.

Verbascum thapsus L. is a medicinal plant and has been used to treat numerous pulmonary diseases, asthma, inflammatory disease, spasmodic coughs and migraine headaches. Several studies have demonstrated that different extracts of V. thapsus present antimicrobial activity. Thus, the goal of this study was to evaluate the genotoxic and cytotoxic activities of a methanolic extract of Verbascum thapsus, using micronucleus test in mouse bone marrow. No toxicity in bone marrow was detected in the extract-treated groups. The methanolic extract of V. thapsus at doses of 100, 300 and 500 mg/kg, did not produce a significant increase in the frequency of MNPCE in bone marrow and neither altered the relationship PCE/NCE respect to negative control. These cytogenotoxic findings contribute the preclinical knowledge of methanolic extract of V. thapsus and provide security in its use as herbal medicine.