Glucosinolates, Glycosidically Bound Volatiles and Antimicrobial Activity of Brassica oleraceae Var. Botrytis, (Soultany Cultivar)

Abstract

Background: Egyptian cauliflower Brassica oleracea, L. var. Botrytis L. Soultany cultivar, is an important edible plant in Mediterranean countries. Only a few researches were focused on antimicrobial activity of its volatiles and glucosinolates. Objective: To evaluate the antimicrobial activity of volatiles and glucosinolates of Egyptian Cauliflower and identify them by GC/MS and HPLC/MS designs. Materials and Methods: The semi-volatile and volatile constituents of were extracted by hydrodistillation from leaves, stems and inflorescences, using a Likens –Nickerson-type apparatus. The extracts from fresh and frozen vegetables were investigated by GC/MS and HPLC/MS. the volatile samples containing glucosinolate degradation products were evaluated for antimicrobial activity using the disc diffusion method. Results: From the fresh leaves extract, a total of 49 compounds were identified, representing 98.79% of the oil. The major constituent was found to be hex-3(Z)-enol (18.86%). From fresh disrupted inflorescence tissues of Egyptian cauliflower 45 compounds were detected, representing 93.37% of the extract. Nonacosane and 11-methoxy   benz(a)anthracene-7,12-dione   were   identified  as  major constituents   of   the hydrodistillation products, representing, respectively, 17.7 and 8.31% of the volatiles.   From frozen inflorescence tissues, dimethyl trisulfide and butylated hydroxy toluene were detected as predominant components representing 15.88 and 9.69% respectively. In the latter, hex-3(Z)-enol was not found to be the major constituent as happened in fresh leaves, but representing 3.88%. From fresh stem tissues, dimethyl trisulphide was detected as major constituent representing a percentage (24.06%) more than present in frozen inflorescence tissues. Twenty two compounds were identified by triple quad HPLC/MS. Volatile samples expressed a wide range of growth inhibition activity against both Gram-positive and Gram-negative bacteria and fungi, showing the highest inhibitory effects against E .coli and K. pneumonia strains. Conclusion: Hydrodistilled compounds present in the stems, leaves and inflorescence tissues of this cultivar has a highly promising antimicrobial activity.

Keywords: Cauliflower, Brassica oleraceae, Glucosinolates, GC/MS, HPLC/MS, Antimicrobial activity.