Abstract
Seven flavonoids have been isolated from the aerial parts of Halostachys caspica C. A. Mey. (Chenopodiaceae) for the first time. By means of physicochemical and spectrometric analysis, they were identified as luteolin (1), chrysin (2), chrysin 7-O-β-D-glucopyranoside (3), quercetin (4), quercetin 3-O-β-D-glucopyranoside (5), isorhamentin-3-O-β-D-glucopyranoside (6), and isorhamentin-3-O-β-D-rutinoside (7). All flavonoids were evaluated to show a broad antimicrobial spectrum of activity on microorganisms including seven bacterial and one fungal species as well as pronounced antioxidant activity. Among them, the aglycones with relatively low polarity had stronger bioactivity than their glycosides. The results suggested that the isolated flavonoids could be used for future development of antimicrobial and antioxidant agents, and also provided additional data for supporting the use of H. caspica as forage.
Highlights
The plant kingdom, with its remarkable diversity of natural compounds, has merited special interest [1]
Seven flavonoids were isolated from the ethyl acetate fraction of the crude ethanol extract of the aerial parts of H. caspica based on a bioassay-guided fractionation
The antioxidant results of flavonoids in this study showed good consistency between the two complementary DPPH radical scavenging and β-carotene-linoleic acid bleaching assays, that indicated the antioxidant activity of aglycones was better than that of their glycosides
Summary
The plant kingdom, with its remarkable diversity of natural compounds, has merited special interest [1] Among these compounds, flavonoids have received much research and development attention [2,3,4]. Our previous study showed that the ethyl acetate fraction of the crude ethanol extract of the aerial parts of H. caspica exhibited an obvious antimicrobial activity [20] In this work, this ethyl acetate fraction of the crude ethanol extract was subjected to bioassay-guided fractionation leading to the isolation of seven flavonoids, including three different flavones and four different flavonols. The antimicrobial activities of these compounds were evaluated by testing their inhibitory ability on seven bacterial and one fungal species by using the dilution-colorimetric assay In addition their antioxidant activity was tested by using two complementary systems, namely the DPPH free radical-scavenging and β-carotene-linoleic acid bleaching assays. Based on their bioactivities and structural characteristics, the structurebioactivity relations of the compounds were examined
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