Avian infectious bronchitis (IB) is a disease that can result in huge economic losses in the poultry industry. The high level of mutations of the IB virus (IBV) leads to the emergence of new serotypes and genotypes, and limits the efficacy of routine prevention. Medicinal plants, or substances derived from them, are being tested as options in the prevention of infectious diseases such as IB in many countries. The objective of this study was to investigate extracts of 15 selected medicinal plants for anti-IBV activity. Extracts of S. montana, O. vulgare, M. piperita, M. officinalis, T. vulgaris, H. officinalis, S. officinalis and D. canadense showed anti-IBV activity prior to and during infection, while S. montana showed activity prior to and after infection. M. piperita, O. vulgare and T. vulgaris extracts had > 60 SI. In further studies no virus plaques (plaque reduction rate 100%) or cytopathogenic effect (decrease of TCID50 from 2.0 to 5.0 log10) were detected after IBV treatment with extracts of M. piperita, D. canadense and T. vulgaris at concentrations of extracts ≥0.25 cytotoxic concentration (CC50) (P < 0.05). Both PFU number and TCID50 increased after the use of M. piperita, D. canadense, T. vulgaris and M. officinalis extracts, the concentrations of which were 0.125 CC50 and 0.25 CC50 (P < 0.05). Real-time PCR detected IBV RNA after treatment with all plant extracts using concentrations of 1:2 CC50, 1:4 CC50 and 1:8 CC50. Delta cycle threshold (Ct) values decreased significantly comparing Ct values of 1:2 CC50 and 1:8 CC50 dilutions (P < 0.05). Many extracts of plants acted against IBV prior to and during infection, but the most effective were those of M. piperita, T. vulgaris and D. canadense .

The aim of this study was to evaluate the impact of forest clear-cutting on the phenolic compounds and antiradical activity of Vaccinium myrtillus, Vaccinium vitis-idaea, and forest litter collected during the vegetation stages in 2 forests types (Pinetum vacciniosumand Pinetum vaccinio-myrtillosum). The Folin-Ciocalteu method, aluminum trichloride colorimetric assay, and 2,2-diphenyl-1-picrylhydrazyl (DPPH) test were applied to perform the total phenolic content (TPC), total flavonoid content (TFC), and antiradical activity analyses of the extracts of the underground and aboveground parts of the plants and forest litter. The TPC content varied from 35.87 to 229.76 mg/g (expressed as rutin equivalents) and 120.03 to 309.64 mg/g in the aboveground extracts of V. myrtillus and V. vitis-idaea, respectively. Remarkably lower amounts of phenolic compounds were determined in the underground extracts of the tested shrubs. The TPC content in the forest litter ranged from 3.12 to 11.89 mg/g. The radical scavenging activity (RSA) varied from 3.12 to 434.68 mg/g; the lowest antiradical activity was determined in the underground extracts, while the highest was in the aboveground extracts of V. myrtillus. The TFC was dependent on the vegetation phase, forest type, and clear-cutting, and varied from 7.97 to 40.18 mg/g in the aboveground extracts of the tested plants. Flavonoids were not detected in the underground extracts of the samples or in the forest litter. The chemometric analysis revealed statistically significant trends of environmental impact on V. myrtillus and V. vitis-idaea at the different vegetation stages. Hypotheses testing showed that the TPC, TFC and RSA expressed statistically significant (α ≤ 0.05) changes in 68%, 60% and 71% of the tested samples after clear-cutting, respectively.

Medicinal plants are reported to possess antiviral activity, but finding the substances that are responsible for antiviral activity in the complex mixture of the plant extract is an extremely difficult task. In this paper a methodology related to the determination of the antiviral properties of medicinal plant extracts and based on phytochemical analysis, antiviral tests and machine learning methods is described. 16 potentially antiviral medicinal plants were selected, and their chemometric characteristics and antiviral properties were investigated. Three different analytical methods were used for chemical analysis: (i) spectrophotometry, (ii) capillary electrophoresis with contactless conductivity detection, and (iii) gas chromatography-mass spectrometry. 14 attributes were obtained describing the composition of the plant extracts. Viral growth inhibition properties were investigated and 8 candidate plant extracts were selected as being active against viruses. Infectious bronchitis virus was used as a model virus. Machine learning techniques including deep neural network classification, classification and regression tree induction and hierarchical clusterization were used for mining the factors that are responsible for antiviral effects. It was determined that (i) phenolic compounds providing high radical scavenging activity and fractions containing high content of phenolic compounds are positively related to antiviral activity in plant extracts, (ii) hydrophilic compounds that are positively charged (pK_a > 4.7) in acidic media and possess medium and low electrophoretic mobility properties are negatively related to antiviral activity in medicinal plants, (iii) phenolic acids with pK_a lower than 4.7 are not related to antiviral activity in the extracts, and (iv) volatile compounds in the extracts, including diversity, quantity and different volatility properties, do not affect the antiviral activity of plant extracts. Following the proposed methodological approach, it is possible to confirm which chemometric attributes are responsible for antiviral activity in medicinal plant extracts.