文摘
Five new carboxymethyl flavonoids named 5-carboxymethyl-3′, 4′, 7-trihydroxyflavone (boldFont">1), (2S)- 5-carboxymethyl-3′, 4′, 7-trihydroxyflavonone (boldFont">2a), (2R)-5-carboxymethyl-3′, 4′, 7-trihydroxyflavonone (boldFont">2b), (2S)-5-carboxymethyl-4′, 7-dihydroxyflavonone (boldFont">3), 5- carbomethoxymethyl-4′, 7-dihydroxyflavone (boldFont">4), and a new chromone named 5-carboxymethyl-7-hydroxychromone (boldFont">5), together with two known compounds 5-carboxymethyl-4′-hydroxyflavone-7-O-β-d-glucopyranoside (boldFont">6), 5-carboxymethyl-4′, 7-dihydroxyflavone (boldFont">7) were isolated from Selaginella moellendorffii Hieron. Their structures including absolute configuration were elucidated by extensive spectroscopic methods and experimental electronic circular dichroism (ECD) spectra. What's worth mentioning is that a carboxymethyl substituent appeared at the C-5 position of all isolated compounds, only recently discovered in genus Selaginella. Compounds boldFont">2a and boldFont">2b were identified as a pair of chiral isomers; compound boldFont">5 was discovered as the first chromone comprising a carboxymethyl side chain. Furthermore, all compounds were evaluated for their antibacterial activities against various Gram-positives and Gram-negatives, and compared to the reference drugs amoxicillin and norfloxacin. As a result, compounds boldFont">3 and boldFont">4 exhibited as potent antimicrobial agents with a broad spectrum, and compound boldFont">5 appeared as the most promising one to combat Gram-positives.
