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SARS-CoV-2 infects host cells by interacting its spike protein with surface angiotensin-converting enzyme 2 (ACE2) receptors, expressed in lung and other cell types. Although several risk factors could explain why some countries have lower incidence and fatality rates than others, environmental factors such as diet should be considered. It has been described that countries with high polyunsaturated fatty acid (PUFA) intake have a lower number of COVID-19 victims and a higher rate of recovery from the disease. Moreover, it was found that linoleic acid, an omega-6 PUFA, could stabilize the spike protein in a closed conformation, blocking its interaction with ACE2. These facts prompted us to perform in silico simulations to determine if other PUFA could also stabilize the closed conformation of spike protein and potentially lead to a reduction in SARS-CoV-2 infection. We found that: (a) countries whose source of omega-3 is from marine origin have lower fatality rates; and (b) like linoleic acid, omega-3 PUFA could also bind to the closed conformation of spike protein and therefore, could help reduce COVID-19 complications by reducing viral entrance to cells, in addition to their known anti-inflammatory effects.

Clerodane, Insect Growth Regulator Activity, AcetylcholinesteraseFrom the aerial parts of Gutierrezia microcephala (Asteraceae), four oxyflavones were iso lated, namely 5,7,2'-trihydroxy-3,6,8,4',5'-pentamethoxyflavone (1); 5,7,4'-trihydroxy-3,6,8-trim ethoxyflavone (2); 5,7,2',4'-tetrahydroxy-3,6,8,5'-tetramethoxyflavone (3); 5,2'-dihydroxy-3,6,7,8,4',5'-hexamethoxyflavone (4), and an ent-clerodane, bacchabolivic acid (5). Compounds 1-5, the synthetic methyl ester (6 ), «-hexane and M eOH extracts were evaluated against the fall armyworm (Spodoptera frugiperda). Gedunin, a known insect growth regulator isolated from Cedrela spp. was used as a positive control. When tested for activity on neonate larvae into the no-choice artificial diet bioassay, flavone (1), clerodane (5), its methyl ester (6 ), M eOH and «-hexane extracts caused significant larval mortality with MC50 of 3.9, 10.7, 3.46. 7.95 and 7.5 ppm at 7 days, respectively, as well as growth reduction. They also increased the developm ent time of surviving larvae and a significant delay in time to pupation and adult emergence. Acute toxicity against adults o f S. frugiperda was also found, 5, 6 , gedunin and «-hexane extract had the most potent activity with L D 50 value of 6.59, 15.05, 10.78, and 12.79 ppm, respectively. In addition, M eO H , n-hexane extracts, 5, 6 and gedunin caused acetylcholinesterase inhibition with 93.7,100,90.2,62.0 and 100% at 50.0 ppm, respectively; whereas 1 -4 exhibited only m oder ate inhibitory activity. Compounds 1 ,5 and 6 showed inhibitory activities comparable with gedu nin. These compounds could be responsible of the insect growth inhibitory activity of this plant.

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An increasing occurrence of resistance in insect pests and high mammal toxicity exhibited by common pesticides increase the need for new alternative molecules. Among these alternatives, bioinsecticides are considered to be environmentally friendly and safer than synthetic insecticides. Particularly, plant extracts have shown great potential in laboratory conditions. However, the lack of studies that confirm their mechanisms of action diminishes their potential applications on a large scale. Previously, we have reported the insect growth regulator and insecticidal activities of secondary metabolites isolated from plants of the Calceolaria genus. Herein, we report an in silico study of compounds isolated from Calceolaria against acetylcholinesterase, prophenoloxidase, and ecdysone receptor. The molecular docking results are consistent with the previously reported experimental results, which were obtained during the bioevaluation of Calceolaria extracts. Among the compounds, phenylethanoid glycosides, such as verbascoside, exhibited good theoretical affinity to all the analyzed targets. In light of these results, we developed an index to evaluate potential multitarget insecticides based on docking scores.

Argentatins, Insect Growth Regulators, Acetylcholinesterase The methanolic extract from aerial parts of Parthenium argentatum, afforded argentatin A and B. These compounds were evaluated for their effect on the fall armyworm (Spodoptera frugiperda). Toosendanin, a commercial insecticide derived from Melia azedarach was used as positive control. When tested for activity, using neonate larvae into the no-choice artificial diet bioassays, argentatin A, argentatin B and methanol extract caused significant growth inhibitory activity with GC50 of 17.8, 36.1 and 6.4 ppm at 7 days, respectively, and increased the development time of surviving larvae in a concentration-dependent manner with RGI values of 0.40, 0.60 and 0.26, at 25.0, 25.0 and 5.0 ppm. respectively. In addition, it was possible to observe in most of the treated groups a significant delay in the time of pupation, adult emergence and deformities. Acute toxicity against adults of S. frugiperda was also found, MeOH extract had the most potent activity with LD50 value of 3.10 ppm. In addition, MeOH extract and argentatin A caused acetylcholinesterase inhibition of 93.7% and 90.0%, at 5.0 and 50.0 ppm, respectively; whereas argentatin B had only slight inhibitory activity. Therefore, the MeOH extract was identified as insecticidal extract from P. argentatum with activity at concentrations above 15.0 ppm.

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