文摘
Five new carboxymethyl flavonoids named 5-carboxymethyl-3′, 4′, 7-trihydroxyflavone (class="boldFont">1), (2S)- 5-carboxymethyl-3′, 4′, 7-trihydroxyflavonone (class="boldFont">2a), (2R)-5-carboxymethyl-3′, 4′, 7-trihydroxyflavonone (class="boldFont">2b), (2S)-5-carboxymethyl-4′, 7-dihydroxyflavonone (class="boldFont">3), 5- carbomethoxymethyl-4′, 7-dihydroxyflavone (class="boldFont">4), and a new chromone named 5-carboxymethyl-7-hydroxychromone (class="boldFont">5), together with two known compounds 5-carboxymethyl-4′-hydroxyflavone-7-O-β-class="smallcaps">d-glucopyranoside (class="boldFont">6), 5-carboxymethyl-4′, 7-dihydroxyflavone (class="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 class="boldFont">2a and class="boldFont">2b were identified as a pair of chiral isomers; compound class="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 class="boldFont">3 and class="boldFont">4 exhibited as potent antimicrobial agents with a broad spectrum, and compound class="boldFont">5 appeared as the most promising one to combat Gram-positives.