Synthesis and Antifungal Activity of 2-(2-Benzoxazolyl)-1-arylethanone and 2-(2-Benzoxazolyl)-1-alkylethanone Derivatives.

To discover more effective antifungal candidates, 33 benzoxazole derivatives, were designed, synthesized, and evaluated for their antifungal activity against seven phytopathogenic fungi by the mycelium growth rate method. Among 33 benzoxazole derivatives had thirteen derivatives no reported, and new derivatives C17 exhibited good inhibitory activity against Phomopsis sp. with EC50 values of 3.26 µM. Structure-activity relationship (SAR) of these derivatives analysis indicated that the substituent played a key role in antifungal activity in ortho-, meta- and para- substituted acetophenones. The preliminary mechanistic exploration demonstrated that C17 might exert its antifungal activity by targeting the mycelia cell membrane, which was verified by the observed changes in mycelial morphology, the formation of extracellular polysaccharides, cellular contents, cell membrane permeability and integrity, among other effects. Furthermore, C17 had potent curative effect against Phomopsis sp. in vivo, which indicated that C17 may be as a novelty potent antifungal agent.

Isolating Antipathogenic Fungal Coumarins from Coriaria nepalensis and Determining Their Primary Mechanism In Vitro.

Through bioassay-guided isolation, eight undescribed coumarins (1-8), along with six reported coumarins (9-14), were obtained from Coriaria nepalensis. The new structures were determined by using IR, UV, NMR, HRESIMS, and ECD calculations. The results of the biological activity assays showed that compound 9 exhibited broad spectrum antifungal activities against all tested fungi in vitro and a significant inhibitory effect on Phytophthora nicotianae with an EC50 value of 3.00 µg/mL. Notably, compound 9 demonstrated greater curative and protective effects against tobacco balack shank than those of osthol in vivo. Thus, 9 was structurally modified to obtain new promising antifungal agents, and the novel derivatives (17b, 17j, and 17k) exhibited better effects on Sclerotinia sclerotiorum than did lead compound 9. Preliminary mechanistic exploration illustrated that 9 could enhance cell membrane permeability, destroy the morphology and ultrastructure of cells, and reduce the exopolysaccharide content of P. nicotianae mycelia. Furthermore, the cytotoxicity results revealed that compound 9 exhibited relatively low cytotoxicity against HEK293 cell lines with an inhibition rate of 33.54% at 30 µg/mL. This research is promising for the discovery of new fungicides from natural coumarins with satisfactory ecological compatibility.

Preventive agents for neurodegenerative diseases from resin of Dracaena cochinchinensis attenuate LPS-induced microglia over-activation.

Our previous research revealed resin of Dracaena cochinchinensis as a candidate for therapy of neurodegenerative diseases. In the present study, the material basis of Chinese Dragon's blood and the primary mechanism of the effective components are discussed. Multiple chromatography and spectra analysis were utilized to identify effective constituents. The production of NO was determined using nitrite assay in BV-2 microglial cells stimulated with lipopolysaccharide (LPS). Cell viability was tested using MTT assay. The mRNA level of inducible nitric oxide synthase (iNOS) was investigated by quantitative real-time PCR (qRT-PCR), and the production of IL-6 and TNF-α in the cell supernatants was tested by ELISA. The bioassay-directed separation of the effective extract of D. cochinchinensis afforded two new compounds, a stilbene-flavane dimer (2) and a quinoid flavonoid (11), in addition to 25 known compounds. The evaluation of their anti-neuroinflammatory activities showed that 5, 9, 12, 13, and 14 could exhibit significant anti-neuroinflammatory effects without cytotoxities at the tested concentration, compared to a positive control, minocycline (21.87 ± 2.36 µM). A primary mechanistic study revealed that the effective components could inhibit over-activation of microglial through decreasing the expressions of iNOS, proinflammatory cytokines IL-6 and TNF-α in LPS- induced BV2 microglial cells. Chalcone 9, homoisoflavane 5 and flavone 12-14 are considered to be responsible for the anti-neuroinflammatory effects of Chinese Dragon's blood. These could inhibit neuroinflammation by reducing the expressions of iNOS, IL-6 and TNF-α in over-activated microglial. Furthermore, the SAR is briefly discussed.