Fitoquímica, atividade antiviral e efeito sobre citocinas pró-inflamatórias de plantas da família Asteraceae visando à identificação de agentes ativos contra o SARS-CoV-2.

Abstract

The COVID-19 pandemic has driven an urgent quest for effective therapies against SARS-CoV-2 capable of combating both viral infection and associated inflammatory responses. Despite the use of vaccines in disease control, their reduced efficacy against new variants underscores the need for therapeutic alternatives. In this context, this study aimed to isolate and identify substances with antiviral activity against SARS-CoV-2 and activity in inhibiting the release of pro-inflammatory cytokines, through screening of plant species from the Asteraceae family. Initially, six ethanolic extracts from Baccharis and Campovassouria species and derived fractions were screened in L929 cells infected with the murine β-coronavirus MHV-3 at non-cytotoxic concentrations (10 and 30 µg/mL). Campovassouria cruciata extract, along with hexane (Hex) and dichloromethane (Dcm) fractions, showed the greatest reduction in viral load. These fractions were also tested in Calu-3 cells infected with SARS-CoV-2, with the Dcm fraction reducing viral load by 1.3 log. Additionally, the potential of extracts and fractions from C. cruciata, Baccharis stylosa, and Baccharis imbricata in inhibiting the release of pro-inflammatory cytokines in IFN-γ and TNF-stimulated A549 cells was evaluated, with dichloromethane fractions from the extracts showing the most promise and thus selected for phytochemical studies. Following successive fractionations, four substances were isolated from C. cruciata Dcm fraction: umbelliferone, 3-epi-leptocarpin, a novel sesquiterpene lactone, in addition to leptocarpin and arturin. From B. stylosa Dcm fraction, a novel flavonoid (3-O-(2-methyl-butyrate)-5,7-di-hydroxy-4'-methoxy-flavone) with a methyl-butyric group as substituent was isolated, alongside the spectral data description of two labdane-type diterpenes ((E)-13-methyl-12-(((9R,10R)-4,4,10-trimethyl-8-methylenedecahydronaphthalen-9-yl)methylene)-2(5H)dione and nicandrona) previously isolated. From B. imbricata Dcm fraction, 12-epi-nicandrodial, reported for the first time in this species, was isolated. Subsequently, all isolated substances were evaluated for their potential to inhibit the release of IL-6 and IL-8 cytokines in IFN-γ and TNF-stimulated A549 lung adenocarcinoma cells, as well as their ability to inhibit reactive oxygen species (ROS) production. All showed concentration-dependent inhibition of cytokine levels, while umbelliferone, the novel flavonoid, and the two diterpenes increased ROS levels, and sesquiterpene lactones reduced them. Finally, the antiviral potential of substances isolated from C. cruciata was demonstrated by reducing viral load in Calu-3 cells infected with SARS-CoV-2 (1.7 to 2.0 log). These findings highlight the promising potential of C. cruciata, B. stylosa, and B. imbricata extracts as valuable sources of molecules with antiviral and anti-inflammatory activities.