RESUMO
The diverse and large-scale application of disinfectants posed potential health risks and caused ecological damage during the 2019-nCoV pandemic, thereby increasing the demands for the development of disinfectants based on natural products, with low health risks and low aquatic toxicity. In the present study, a few natural naphthoquinones and their derivatives bearing the 1,4-naphthoquinone skeleton were synthesized, and their antibacterial activity against selected bacterial strains was evaluated. In vitro antibacterial activities of the compounds were investigated against Escherichia coli and Staphylococcus aureus. Under the minimum inhibitory concentration (MIC) of ⩽ 0.125 µmol/L for juglone (1a), 5,8-dimethoxy-1,4-naphthoquinone (1f), and 7-methyl-5-acetoxy-1,4-naphthoquinone (3c), a strong antibacterial activity against S. aureus was observed. All 1,4-naphthoquinone derivatives exhibited a strong antibacterial activity, with MIC values ranging between 15.625 and 500 µmol/L and EC50 values ranging between 10.56 and 248.42 µmol/L. Most of the synthesized compounds exhibited strong antibacterial activities against S. aureus. Among these compounds, juglone (1a) showed the strongest antibacterial activity. The results from mechanistic investigations indicated that juglone, a natural naphthoquinone, caused cell death by inducing reactive oxygen species production in bacterial cells, leading to DNA damage. In addition, juglone could reduce the self-repair ability of bacterial DNA by inhibiting RecA expression. In addition to having a potent antibacterial activity, juglone exhibited low cytotoxicity in cell-based investigations. In conclusion, juglone is a strong antibacterial agent with low toxicity, indicating that its application as a bactericidal agent may be associated with low health risks and aquatic toxicity. Electronic Supplementary Material: Supplementary material is available in the online version of this article at 10.1007/s11783-023-1631-2 and is accessible for authorized users.
RESUMO
BACKGROUND: Cancer is a malignant disease that causes millions of deaths each year worldwide. As one of the cancer therapeutic strategies, chemotherapy is a means to destroy rapidly dividing cells. The main problem with cancer chemotherapy is the lack of selectivity of conventional chemotherapeutic drugs, leading to toxicity towards normal cells. Therefore, the discovery of anticancer agents with selectivity for fast-growing cancer cells was desirable. OBJECTIVE: In this study, we report the synthesis and identification of the novel 5-benzyl juglone as a potential anticancer agent with selectivity toward certain cancer cell lines. METHODS: An efficient synthetic method for 5-benzyl juglone has been established. The proliferation of cancer cell lines and a normal cell line treated by the target compound were studied using an MTT assay. In addition, the cell cycle arrest and apoptosis were determined by flow cytometry. RESULTS: Based on the Diels-Alder (D-A) reaction between 3,6-dimethoxy benzyne intermediate with furan, further acid-catalyzed intramolecular rearrangement and CAN-mediated oxidation, a convenient synthesis of 5-benzyl juglone has been achieved with high overall yield. The results from in vitro biological evaluation indicated that the juglone derivative exhibited potent antiproliferative activity against HCT-15 human colorectal cancer cells with an IC50 value of 12.27 µM. It exerted high inhibitory activity toward MCF-7 human breast cancer cells and, to a much lesser extent, to corresponding MCF-10A human breast epithelial normal cells with the IC50 ratio (IC50 in MCF-7 divided by IC50 in MCF-10A) of 0.62. CONCLUSION: The mechanistic investigations indicated that 5-benzyl juglone could induce cell cycle arrest at the G0/G1 phase and promote apoptosis of HCT-15 cells. The apoptotic effects possibly also contributed to its higher selectivity toward cancer cells than normal cell lines.