Discovery of Cysteine and Its Derivatives as Novel Antiviral and Antifungal Agents

Synthesis, Anti-TMV Activities, and Action Mechanisms of a Novel Cytidine Peptide Compound

Cytidine has a broad range of applications in the pharmaceutical field as an intermediate of antitumor or antiviral agent. Here, a series of new cytidine peptide compounds were synthesized using cytidine and Boc group-protected amino acids and analyzed for their antiviral activities against tobacco mosaic virus (TMV). Among these compounds, the structure of an effective antiviral cytidine peptide SN11 was characterized by 1H NMR, 13C NMR, and high-resolution mass spectrometer. The compound SN11 has a molecular formula of C15H22N6O8 and is named 2-amino-N-(2- ((1- (3,4-dihydroxy-5-(hydroxymethyl) tetrahydrofuran-2-yl) -2-oxo-1,2-dihydropyrimidin-4-yl) amino) -2-oxyethyl) amino). The protection, inactivation, and curation activities of SN11 at a concentration of 500 μg/mL against TMV in Nicotiana glutinosa were 82.6%, 84.2%, and 72.8%, respectively. SN11 also effectively suppressed the systemic transportation of a recombinant TMV carrying GFP reporter gene (p35S-30B:GFP) in Nicotiana benthamiana by reducing viral accumulation to 71.3% in the upper uninoculated leaves and inhibited the systemic infection of TMV in Nicotiana tabacum plants. Furthermore, the results of RNA-seq showed that compound SN11 induced differential expression of genes involved in the biogenesis and function of ribosome, plant hormone signal transduction, plant pathogen interaction, and chromatin. These results validate the antiviral mechanisms of the cytidine peptide compound and provide a theoretical basis for their potential application in the management of plant virus diseases.

Chiral hydroxymethyl-1H,3H-pyrrolo[1,2-c]thiazoles: the search for selective p53-activating agents for colorectal cancer therapy

MANIO is an efficient p53-activating anticancer agent with remarkable selectivity to the p53 pathway and promising antitumor activity against colorectal cancer (CRC). Herein, a library of novel MANIO derivatives, including hydroxymethyl- and bis(hydroxymethyl)-1H,3H-pyrrolo[1,2-c]thiazoles, was synthesized by rational structural modulation. The antiproliferative activity of twenty derivatives was evaluated in a panel of human CRC cells with different p53 status. From this library, five compounds with R- and S-configuration and with aromatic or heteroaromatic groups at position 3, including the enantiomer of MANIO, were identified as selective towards p53-expressing cancer cells. On the other hand, two compounds with S-configuration, 6-hydroxymethyl- and 7-hydroxymethyl-5-methyl-3-phenyl-1H,3H-pyrrolo[1,2-c]thiazoles, showed high cytotoxicity against WTp53-expressing HCT116 colon cells but, unlike MANIO, exhibited p53-independent inhibitory activity in CRC. The results described provide relevant structural and pharmacophoric data for the design of new p53-activating agents for precision therapy of CRC or other p53-related cancers harboring both wild-type or mutated p53 forms.

High inhabitation activity of CMCS/Phytic acid/Zn2+ nanoparticles via flash nanoprecipitation (FNP) for bacterial and fungal infections

Plant diseases prompted by fungi and bacteria are one of the most serious threats to global crop production and food security. The destruction of these infections posed a major challenge to plant protection by chemical control. Herein, we develop CMCS/PA/Zn²⁺ nanoparticles (NPs) using carboxymethyl chitosan (CMCS), phytic acid (PA) and metal ions (Zn²⁺) via flash nanoprecipitation (FNP) strategy. Metal complexes of PA with specified antibacterial and antifungal activities are expected to hold the potential and play a significant role in antimicrobial treatment. The size and size distribution of NPs was confirmed through Dynamic and Static Light Scatterer (DSLS). In acidic-infection microenvironment, the CMCS/PA/Zn²⁺ NPs can disintegrate and release Zn²⁺ in situ thus stimulated the corresponding antimicrobial activity. These CMCS/PA/Zn²⁺ NPs showed outstanding antibacterial efficacy (98 %) against S. aureus and E. coli bacteria in vitro, as well as an impressive antifungal efficacy of 98 % and 81 % against R. solani and B. cinerea at 50 μg/mL respectively. This study contributes a prospective idea to the development of organic-inorganic hybrid NPs as environmentally-friendly and safe agricultural antimicrobials.

Natural Products for Pesticides Discovery: Structural Diversity Derivation and Biological Activities of Naphthoquinones Plumbagin and Juglone

Plant diseases and insect pests seriously affect the yield and quality of crops and are difficult to control. Natural products are an important source for the discovery of new pesticides. In this work, naphthoquinones plumbagin and juglone were selected as parent structures, and a series of their derivatives were designed, synthesized and evaluated for their fungicidal activities, antiviral activities and insecticidal activities. We found that the naphthoquinones have broad-spectrum anti-fungal activities against 14 types of fungus for the first time. Some of the naphthoquinones showed higher fungicidal activities than pyrimethanil. Compounds I, I-1e and II-1a emerged as new anti-fungal lead compounds with excellent fungicidal activities (EC₅₀ values: 11.35-17.70 µg/mL) against Cercospora, arachidicola Hori. Some compounds also displayed good to excellent antiviral activities against the tobacco mosaic virus (TMV). Compounds I-1f and II-1f showed similar level of anti-TMV activities with ribavirin, and could be used as new antiviral candidates. These compound also exhibited good to excellent insecticidal activities. Compounds II-1d and III-1c displayed a similar level of insecticidal activities with matrine, hexaflumuron and rotenone against Plutella xylostella. In current study, plumbagin and juglone were discovered as parent structures, which lays a foundation for their application in plant protection.

Discovery of Flavone Derivatives Containing Carboxamide Fragments as Novel Antiviral Agents

Plant virus diseases seriously affect the yield and quality of agricultural products, and their prevention and control are difficult. It is urgent to develop new and efficient antiviral agents. In this work, a series of flavone derivatives containing carboxamide fragments were designed, synthesized, and systematically evaluated for their antiviral activities against tobacco mosaic virus (TMV) on the basis of a structural-diversity-derivation strategy. All the target compounds were characterized by 1H-NMR, 13C-NMR, and HRMS techniques. Most of these derivatives displayed excellent in vivo antiviral activities against TMV, especially 4m (inactivation inhibitory effect, 58%; curative inhibitory effect, 57%; and protection inhibitory effect, 59%), which displayed similar activity to ningnanmycin (inactivation inhibitory effect, 61%; curative inhibitory effect, 57%; and protection inhibitory effect, 58%) at 500 μg mL-1; thus, it emerged as a new lead compound for antiviral research against TMV. Antiviral mechanism research by molecular docking demonstrated that compounds 4m, 5a, and 6b could interact with TMV CP and disturb virus assembly.

Design, synthesis and biological activities of echinopsine derivatives containing acylhydrazone moiety

Based on the broad-spectrum biological activities of echinopsine and acylhydrazones, a series of echinopsine derivatives containing acylhydrazone moieties have been designed, synthesized and their biological activities were evaluated for the first time. The bioassay results indicated that most of the compounds showed moderate to good antiviral activities against tobacco mosaic virus (TMV), among which echinopsine (I) (inactivation activity, 49.5 ± 4.4%; curative activity, 46.1 ± 1.5%; protection activity, 42.6 ± 2.3%) and its derivatives 1 (inactivation activity, 44.9 ± 4.6%; curative activity, 39.8 ± 2.6%; protection activity, 47.3 ± 4.3%), 3 (inactivation activity, 47.9 ± 0.9%; curative activity, 43.7 ± 3.1%; protection activity, 44.6 ± 3.3%), 7 (inactivation activity, 46.2 ± 1.6%; curative activity, 45.0 ± 3.7%; protection activity, 41.7 ± 0.9%) showed higher anti-TMV activity in vivo at 500 mg/L than commercial ribavirin (inactivation activity, 38.9 ± 1.4%; curative activity, 39.2 ± 1.8%; protection activity, 36.4 ± 3.4%). Some compounds exhibited insecticidal activities against Plutella xylostella, Mythimna separate and Spodoptera frugiperda. Especially, compounds 7 and 27 displayed excellent insecticidal activities against Plutella xylostell (mortality 67 ± 6% and 53 ± 6%) even at 0.1 mg/L. Additionally, most echinopsine derivatives exhibited high fungicidal activities against Physalospora piricola and Sclerotinia sclerotiorum.

Autoxidation Products of the Methanolic Extract of the Leaves of Combretum micranthum Exert Antiviral Activity against Tomato Brown Rugose Fruit Virus (ToBRFV)

Tomato brown rugose fruit virus (ToBRFV) is a new damaging plant virus of great interest from both an economical and research point of view. ToBRFV is transmitted by contact, remains infective for months, and to-date, no resistant cultivars have been developed. Due to the relevance of this virus, new effective, sustainable, and operator-safe antiviral agents are needed. Thus, 4-hydroxybenzoic acid was identified as the main product of the alkaline autoxidation at high temperature of the methanolic extract of the leaves of C. micranthum, known for antiviral activity. The autoxidized extract and 4-hydroxybenzoic acid were assayed in in vitro experiments, in combination with a mechanical inoculation test of tomato plants. Catechinic acid, a common product of rearrangement of catechins in hot alkaline solution, was also tested. Degradation of the viral particles, evidenced by the absence of detectable ToBRFV RNA and the loss of virus infectivity, as a possible consequence of disassembly of the virus coat protein (CP), were shown. Homology modeling was then applied to prepare the protein model of ToBRFV CP, and its structure was optimized. Molecular docking simulation showed the interactions of the two compounds, with the amino acid residues responsible for CP-CP interactions. Catechinic acid showed the best binding energy value in comparison with ribavirin, an anti-tobamovirus agent.