Three new terpenes with potential antibacterial and anti-COVID-19 activities from the stems of Eurya chinensis R. Br.

The extract of the stems of Eurya chinensis R. Br. yielded three new terpenes (1-3) including two diterpenes and one triterpene, named euryachins C-E, as well as three known diterpenes (4-6). The structures of these novel compounds were elucidated via spectroscopic analysis, especially IR, NMR spectroscopy and HRESIMS data. Besides, all the isolated compounds were evaluated for antibacterial activity against Escherichia coli, Bacillus cereus, Staphylococcus aureus and Methicillin-resistant S. aureus (MRSA). Additionally, the inhibitive activity of the isolated compounds against COVID-19 was studied in vitro. As a result, compounds 1-6 were endowed with profound antibacterial activity. Especially, the MIC values of compounds 3 and 5 both were 0.78 µg/mL, the same antibacterial activity as Vancomycin. In the anti-COVID-19 assay, the IC50 values of compounds 3-5 were ranging from 4 to 8 µM, which were equivalent to the positive control.