ABSTRACT
ABSTRACT Equisetum arvense, a fern species possesses a number of pharmaceutical prospective. In the present study, a total of 103 endophytic bacteria isolated from E. arvense and were evaluated for their anticandidal property against five Candida species, two C. albicans, C. glabrata, C. saitoana and C. geochares. Out of them fifty one were identified as per the morphological and molecular characterisation using 16S rRNA gene sequencing and among them, ten promising endophytic bacteria were mentioned in the present study. Among ten endophytic bacteria, Psychrobacillus insolitus and Curtobacterium oceanosedimentum exerted highest anticandidal effect against C. albicans KACC 30062 and C. glabrata KBNO6P00368, with diameter of inhibition zones of 21.30±0.41 and 18.24±0.12 mm, respectively. When the endophytic bacteria cultures were successively fractionated using different solvents, only the butanol fraction of Psychrobacillus insolitus and Curtobacterium oceanosedimentum had anticandidal activity, with inhibition zones of 20.12±0.28 mm and 12.33±0.11 mm, respectively. The minimum inhibitory concentration (MIC) and minimum fungicidal concentration (MFC) values of the butanol fractions ranged from 250 to 500 and 500 to 1,000 µg/mL, respectively. Scanning electron microscope (SEM) analysis showed impaired membrane of C. albicans and C. glabrata at the MIC, indicating that butanol extract lysed the cell membrane and caused cell death. The endophytic bacteria derived from E. arvense can be a valuable resource for the development of natural anticandidal agents to manage candidiasis.
ABSTRACT
Objective:To evaluate inhibitory potential of sevenKorean thistles against the advanced glycation endproducts(AGE) formation as well as to identify responsible compounds from the most active species.Methods:We used anin vitroAGE inhibition assay to evaluate the anti-diabetic complication potential of the methanol extracts of the selectedKorean thistles.Results:Among the sevenKorean thistles, the leaves ofCirsium maackii(C. maackii) exhibited the most significant inhibitory activity againstAGE formation.By means of bioassay-directed fractionation, a lignan, chlorogenic acid and14 flavonoids were isolated from the active ethyl acetate soluble fraction of a methanol extract fromC. maackii leaves.Luteolin and its5-O-glucoside have been previously isolated; however, a lignan and13 known compounds were isolated for the first time fromC. maackiileaves in this study.Most of the isolated compounds exhibited inhibitory activities against potentialAGE formation.Among them, cernuoside was shown to be the most potentAGE inhibitor with anIC50 value of21.21 μmol/L.Most importantly, two major flavonoids, luteolin and its5-O-glucoside, also significantly inhibitedAGE formation, withIC50 values of 36.33 and37.47 μmol/L, respectively.Structure activity relationship revealed that the presence of free3' and4' dihydroxyl group in flavonoids skeleton played an important role inAGE inhibition. Conclusions:These results indicate thatC. maackii andC. maackii-derived flavonoids might be explored further to develop therapeutic agents for the prevention of diabetic complications due to their significant inhibitory activity againstAGE formation.