Exploration of Baicalein-Core Derivatives as Potent Antifungal Agents: SAR and Mechanism Insights.

Baicalein (BE), the major component of Scutellaria Baicalensis, exhibited potently antifungal activity against drug-resistant Candida albicans, and strong inhibition on biofilm formation. Therefore, a series of baicalein-core derivatives were designed and synthesized to find more potent compounds and investigate structure-activity relationship (SAR) and mode of action (MoA). Results demonstrate that A4 and B5 exert a more potent antifungal effect (MIC80 = 0.125 µg/mL) than BE (MIC80 = 4 µg/mL) when used in combination with fluconazole (FLC), while the MIC80 of FLC dropped from 128 µg/mL to 1 µg/mL. SAR analysis indicates that the presence of 5-OH is crucial for synergistic antifungal activities, while o-dihydroxyls and vic-trihydroxyls are an essential pharmacophore, whether they are located on the A ring or the B ring of flavonoids. The MoA demonstrated that these compounds exhibited potent antifungal effects by inhibiting hypha formation of C. albicans. However, sterol composition assay and enzymatic assay conducted in vitro indicated minimal impact of these compounds on sterol biosynthesis and Eno1. These findings were further confirmed by the results of the in-silico assay, which assessed the stability of the complexes. Moreover, the inhibition of hypha of this kind of compound could be attributed to their effect on the catalytic subunit of 1,3-ß-d-glucan synthase, 1,3-ß-d-glucan-UDP glucosyltransferase and glycosyl-phosphatidylinositol protein, rather than inhibiting ergosterol biosynthesis and Eno1 activity by Induced-Fit Docking and Molecular Dynamics Simulations. This study presents potential antifungal agents with synergistic effects that can effectively inhibit hypha formation. It also provides new insights into the MoA.

Synthesis of baicalein derivatives and evaluation of their antiviral activity against arboviruses.

Natural plant-derived baicalein which is extracted from Chinese herb Scutellaria baicalensis Georgi belongs to the flavonoid compounds and possesses multiple pharmacological activities. In this study, we designed and synthesized new series of derivatives of baicalein (BE) through catalytic coupling reactions, and screened for their antiviral activity against arboviruses including Chikungunya virus (CHIKV), West Nile virus (WNV) or Zika virus (ZIKV). Our results revealed for the first time that BE and its derivatives had potent anti-CHIKV, anti-WNV and anti-ZIKV effects. And modification of 8 or 4' position could lead to obtain potent antiviral compounds against CHIKV, WNV and ZIKV with lower cytotoxicity. Among the baicalein derivatives, C3 and F3 showed the most potent antiviral activities against CHIKV, WNV and ZIKV, which were 5-10 times more potent than baicalein. Our findings will provide research basis for the development of baicalein derivatives as effective antiviral agents.