Antioxidant and Cytotoxic Activities of Usnea barbata (L.) F.H. Wigg. Dry Extracts in Different Solvents

Lichens represent a significant source of antioxidants due to numerous metabolites that can reduce free radicals. Usnea barbata (L.) F.H. Wigg. has been recognized and used since ancient times for its therapeutic effects, some of which are based on its antioxidant properties. The present study aims to analyze the phytochemical profile and to evaluate the antioxidant and cytotoxic potential of this lichen species. Five dry extracts of U. barbata (UBDE) in different solvents (acetone, ethyl acetate, ethanol, methanol, water) were prepared by refluxing at Soxhlet to achieve these proposed objectives and to identify which solvent is the most effective for the extraction. The usnic acid content (UAC) was quantified by ultra-high performance liquid chromatography (UHPLC). The total polyphenols content (TPC) and tannins content (TC) were evaluated by spectrophotometry, and the total polysaccharides (PSC) were extracted by a gravimetric method. The 2,2-diphenyl-1-picryl-hydrazyl-hydrate (DPPH) free radical method was used to assess the antioxidant activity (AA) and the Brine Shrimp Lethality (BSL) assay was the biotest for cytotoxic activity evaluation. The ethyl acetate extract had the highest usnic acid content, and acetone extract had the highest content of total polyphenols and tannins. The most significant antioxidant effect was reported to methanol extract, and all the extracts proved high cytotoxicity. The water extract has the lowest cytotoxicity because usnic acid is slightly soluble in this solvent, and it was not found at UHPLC analysis. All extracts recorded a moderate correlation between the content of usnic acid, polyphenols, tannins, and AA; furthermore, it has been observed that the cytotoxicity varies inversely with the antioxidant effect.

Discovery of Dithioacetal Derivatives Containing Sulfonamide Moiety of Novel Antiviral Agents by TMV Coat Protein as a Potential Target

Tobacco mosaic virus coat protein (TMV CP) plays an important role in viral replication, translation, and intracellular and intercellular movements. Thus, TMV CP could be regarded as a potential target for antiviral agents. In this study, in order to find out whether dithioacetal derivatives act on the CP target, a series of dithioacetal derivatives containing sulfonamide moiety was first designed and synthesized. Bioassay results demonstrated that Y14, Y18, and Y21 exhibited excellent activities against TMV, with half-maximal effective concentrations (EC₅₀) of the curative, protective, and inactivate activities being 183.0 ± 3.2, 252.3 ± 2.6, and 63.8 ± 1.2 μg/mL, 270.6 ± 3.7, 249.7 ± 3.5, and 57.7 ± 1.4 μg/mL, and 329.5 ± 1.5, 269.2 ± 3.7, and 48.1 ± 2.0 μg/mL for Y14, Y18, and Y21, respectively, which were higher than those for the control agents ningnanmycin (331.0 ± 2.8, 271.0 ± 2.8, and 77.4 ± 1.3 μg/mL, respectively) and d2 (471.5 ± 1.4, 447.2 ± 2.1, and 91.7 ± 1.8 μg/mL, respectively). Transmission electron microscopy showed that the particle morphology of TMV was destroyed by Y21, and microscale thermophoresis (MST) showed that Y21 bonded to CP with a dissociation constant (K _d) of 9.7 ± 1.7 μM. Then, molecular docking and MST further illustrated that Y21 had a weak binding affinity with the TMV mutant protein (K _d = 561.3 ± 83.2 μM). Thus, we deduced that the dithioacetal derivative Y21 may inhibit TMV activity by binding TMV CP. This work provides some new insights for the design and optimization of novel anti-TMV agents.

Curdepsidone A, a Depsidone from the Marine-Derived Endophytic Fungus Curvularia sp. IFB-Z10

A new depsidone, curdepsidone A (1), was isolated form the culture extracts of curvularia sp. IFB-Z10, a white croaker associated fungus. The structure of 1 was elucidated on the basis of extensive spectroscopic analyses (HRESIMS, 1D and 2D NMR). Compound 1 showed significant cytotoxicity against human hepatoma cell lines BEL7402 and BEL7402/5- FU with IC50 values of 9.85 μM and 2.46 μM, respectively.