Antibacterial furan derivatives from the flowers of Chrysanthemum indicum L.

Furan derivatives are recognized for their diverse biological activities, particularly their antimicrobial properties. In this study, three new furan derivatives were isolated from acid-treated Chrysanthemum indicum flowers. The structures were elucidated using spectroscopic techniques and identified as methyl (E)-3-((5-(methoxymethyl)furan-2-yl)methylene)-4-oxopentanoate (1), methyl (Z)-3-((5-(methoxymethyl)furan-2-yl)methylene)-4-oxopentanoate (2), and methyl (E)-3-(furan-2-ylmethylene)-4-oxopentanoate (3). These compounds were evaluated for antibacterial activity against Vibrio spp. and Microcystis aeruginosa. Compound 3 showed the highest inhibition (63.5%) against M. aeruginosa at 50 μg/mL, with compounds 1 and 2 demonstrating lower activities (36.1% and 58.3%, respectively). The structural difference between compounds 1 and 2, limited to the double bond geometry, likely contributes to their varying efficacies. These findings indicate that furan derivatives from C. indicum could be promising candidates for antimicrobial applications, particularly in aquaculture.