COVID-19, the highly contagious novel disease caused by SARS-CoV-2, has become a major international concern as it has spread quickly all over the globe. However, scientific knowledge and therapeutic treatment options for this new coronavirus remain limited. Although previous outbreaks of human coronaviruses (CoVs) such as SARS and MERS stimulated research, there are, to date, no antiviral therapeutics available that specifically target these kinds of viruses. Natural compounds with a great diversity of chemical structures may provide an alternative approach for the discovery of new antivirals. In fact, numerous flavonoids were found to have antiviral effects against SARS-and MERS-CoV by mainly inhibiting the enzymes 3-chymotrypsin-like protease (3CLpro) and papain-like protease (PLpro). In this review, we specifically focused on the search for flavonoids, polyphenolic compounds, which are proven to be effective against human CoVs. We therefore summarized and analyzed the latest progress in research to identify flavonoids for antiviral therapy and proposed strategies for future work on medicinal plants against coronaviruses such as SARS-CoV-2. We discovered quercetin, herbacetin, and isobavachalcone as the most promising flavonoids with anti-CoV potential.

Reynoutria japonica Houtt. is a critical invasive alien plant in Europe and North America with a drastic impact on native flora. However, R. japonica has medicinal potential, especially as a source of stilbenes. In order to explore the potential of simple extractions of R. japonica, we conducted qualitative and quantitative analyses of fresh R. japonica rhizome infusion, decoction, and macerates with ethanol by UHPLC-DAD-ESI-MSn and UHPLC-DAD, with a focus on major constituent groups of stilbenes and anthranoids. Since R. japonica rhizome extracts showed antimicrobial potential in the past, we also evaluated the antimycobacterial effect of raw R. japonica extracts for the first time against Mycobacterium smegmatis. Of thirty-four characterized substances, six were stilbenes and twelve anthranoids. The main constituents, four trans-stilbenes and eight anthranoids, were quantified in a validated UHPLC-DAD method. The 38% ethanol macerate showed high stilbene (155.078 mg/100 g fluid extract) and low anthranoid content (5.420 mg/100 g fluid extract), while decoction showed the highest anthranoids. Antimycobacterial testing gave good results for all macerates (MIC 256 µg/mL) and trans-resveratrol (64 µg/mL). Extraction and enrichment of stilbenes from fresh plant material by simple extraction methods with food-grade solvents might encourage consideration of wild harvest of rhizomes over classic means of eradication of R. japonica.

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Leafcutter ants live in symbiosis with fungi they grow for food and different bacteria they use for protection against fungal parasites. Some workers are covered with a layer of bacteria like Pseudonocardia, but the behavior of these workers has been the subject of little research. In order to obtain a clearer understanding of this phenomenon in Acromyrmex octospinosus, two experiments were conducted with majors, minors, workers with little bacterial layer and workers with a well-developed bacterial layer. In a first step, scan sampling was used to distinguish the preferred location of workers with bacterial coats, compared to the preferences of their nestmates. Finally, 21 behavior patterns of workers with a bacterial layer on their integument were investigated through focal observations and compared to the behavior of their nestmates. Our findings suggest that workers covered with a high amount of Pseudonocardia differ from their sisters in their preference of location, in that they significantly prefer the bottom part of the nest and cannot be found outside the fungus chamber in the feeding area or the waste area. Additionally, these ants show more fungus grooming and are groomed by nestmates more often than the other workers. These results suggest that workers with an external bacterial layer evolved behavioral specialization.