Antiviral activity in vitro of two preparations of the herbal medicinal product Sinupret® against viruses causing respiratory infections

Abstract

Sinupret(®), a herbal medicinal product made from Gentian root, Primula flower, Elder flower, Sorrel herb, and Verbena herb is frequently used in the treatment of acute and chronic rhinosinusitis and respiratory viral infections such as common cold. To date little is known about its potential antiviral activity. Therefore experiments have been performed to measure the antiviral activity of Sinupret(®) oral drops (hereinafter referred to as "oral drops") and Sinupret(®) dry extract (hereinafter referred to as "dry extract"), in vitro against a broad panel of both enveloped and non-enveloped human pathogenic RNA and DNA viruses known to cause infections of the upper respiratory tract: influenza A, Chile 1/83 (H1N1) virus (FluA), Porcine Influenza A/California/07/2009 (H1N1) virus (pFluA), parainfluenza type 3 virus (Para 3), respiratory syncytial virus, strain Long (RSV), human rhinovirus B subtype 14 (HRV 14), coxsackievirus subtype A9 (CA9), and adenovirus C subtype 5 (Adeno 5). Concentration-dependent antiviral activity (EC(50) between 13.8 and 124.8 μg/ml) of Sinupret(®) was observed against RNA as well as DNA viruses independent of a viral envelope. Remarkable antiviral activity was shown against Adeno 5, HRV 14 and RSV in which dry extract was significantly superior to oral drops. This could be ascertained with different assays as plaque-reduction assays in plaque forming units (PFU), the analyses of a cytopathogenic effect (CPE) and with enzyme immunoassays (ELISA) to determine the amount of newly synthesised virus. Our results demonstrate that Sinupret(®) shows a broad spectrum of antiviral activity in vitro against viruses commonly known to cause respiratory infections.

Graphical abstract

Fig. 1

Antiviral activity of two Sinupret^® preparations against a broad panel of viruses. To test the efficacy of the two Sinupret^® preparations – oral drops and dry extract – on virus replication, virus susceptible cells (MDCK, HEp-2, HeLa and BGM) were infected with a multiplicity of infection (M.O.I.) of 0.0004 (FluA, Para 3, RSV, HRV and CA9) or 0.008 (Adeno 5), without or in presence of five descending non-cytotoxic concentrations of the test substances oral drops (open squares) and dry extract (closed triangles). The antiviral activity (y-axis, % virus inhibition) of the test candidates (x-axis, concentration in μg/ml) was determined in plaque-reduction assays (PFU) for FluA, Para 3, RSV, HRV 14, and CA9 or in analyses of a cytopathogenic effect (CPE) for Adeno 5. The relative inhibitions (% inhibition, ordinate) were calculated by analysing the number of plaques or lesions of the viral CPE of the respective groups and standardised by the virus control representing 100% infectivity (0% inhibition). Positive controls confirmed the procedure (FluA, 5 μg/ml amantadine, 58% inhibition; Para 3, laboratory standard 10 μg/ml, 57% inhibition; HRV 14, laboratory standard 20 μg/ml, 54% inhibition; Adeno 5, laboratory standard 7.5 μg/ml, 57% inhibition; RSV, 6 μg/ml ribavirin, 60% inhibition). All data represent means and SEM from two independent experiments with two (Adeno 5, RSV) or three (FLuA, Para 3, HRV 14 and CA9) replicates. Stars indicate statistically significant differences for the EC₅₀ values between dry extract and oral drops (***p < 0.001).

Fig. 2

Ascertainment of antiviral activity of two Sinupret^® preparations with different assays. To test the efficacy of the two Sinupret^® preparations – oral drops and dry extract – HEp-2 cells were infected with RSV (M.O.I. of 0.0004) or with Adeno 5 (M.O.I. of 0.008). After infection, cell monolayers were incubated without (medium-control) or in the presence of five descending non-cytotoxic concentrations (x-axis, μg/ml) of the test substances oral drops and dry extract. The antiviral activity of Sinupret^® against the viruses was determined with plaque reduction assays in plaque forming units (PFU) for RSV or by analyses of a cytopathogenic effect (CPE) for Adeno 5 (open columns) and with the quantification of the amount of newly synthesised virus by enzyme immunoassays (ELISA; striped columns). The relative inhibition (y-axis, % inhibition) was calculated by analysing the number of plaques, the lesions of the viral CPE or the amount of the viral proteins of the respective groups and standardised by the virus control representing 100% infectivity (0% inhibition). The results of the antiviral activity against RSV are shown in the upper, against Adeno 5 in the lower panels. Positive controls confirmed the procedure (Adeno 5, laboratory standard 7.5 μg/ml, CPE 57% and ELISA 53% inhibition; RSV 6 μg/ml Ribavirin, PFU 60% and ELISA 57% inhibition). All data represent means and SEM from two independent experiments with two (PFU and CPE) to three (ELISA) replicates.

Fig. 3

Antiviral activity of a Sinupret^® preparation against human and porcine influenza virus. To test the efficacy of one Sinupret^® preparation – dry extract – on virus replication, virus susceptible cells (MDCK) were infected with a multiplicity of infection (M.O.I.) of 0.0004 (FluA) or 0.0008 (pFluA), without or in presence of six descending non-cytotoxic concentrations of the test substance dry extract. The antiviral activity (y-axis, % virus inhibition) of the test candidate (x-axis, concentration in μg/ml) was determined in plaque-reduction assays (PFU) for FluA (closed triangles) and pFluA (closed circles). The relative inhibitions (% inhibition, ordinate) were calculated by analysing the number of plaques of the respective groups and standardised by the virus control representing 100% infectivity (0% inhibition). Positive controls confirmed the procedure (FluA, amantadine 5 μg/ml, 58% inhibition; pFluA, amantadine 6 μg/ml, 65% inhibition). All data represent means and SEM from two independent experiments with two to three replicates.