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Two novel bioactive glucosinolates from Broccoli (Brassica oleracea L. var. italica) florets

Abstract:

Two novel glucosinolates along with one known glucosinolate were isolated from Broccoli (Brassica oleracea L. var. italica) florets. Their structures were established mainly by 1D (1H and 13C NMR), 2D NMR ( 1H-1H COSY, DEPT 135°, HSQC and HMBC), and Tandem MS-MS spectrometric data as 2-mercaptomethyl sulfinyl glucosinolate [(Z)-4-(methylsulfinyl)-N-(sulfooxy)-2-((2′S,3′R,4′S, 5′S,6′R)-3′,4′,5′-trihydroxy- 6′(hydroxylmethyl)-2′-mercapto tetrahydro-2H-pyran-2-yl) butane amide] 1, (Z)-1-((2S,5S)-5-hydroxytetra-hydro-2H-pyran-2-ylthio)-2-(1H-indol-3- yl) ethylidene amino sulfate 2 and a known cinnamoyl [6′-O-trans- (4″-hydroxy cinnamoyl)4-(methylsulphinyl)butyl glucosinolate] 3. Compound 1 exhibited scavenging activity against DPPH with an inhibitory concentration IC50 of 20 mM, whereas compound 3 was a weak antioxidant when compared to the standard quercetin (5 mM) as a positive control. Both the compounds showed a significant and similar antimicrobial activity against Staphylococcus aureus with an IC50 of <625 μg/mL when compared to antibiotic duricef. Against Salmonella typhimurium the IC50 of 1 and 3 was determined as <625 μg/mL and <1250 μg/mL, respectively, when compared to ampicillin (IC50 ≤39 μg/mL) as a positive control. © 2012 Elsevier Ltd. All rights reserved.