Antioxidant, antimicrobial and antiproliferative activity of Brassica oleracea varieties broccoli, cauliflower and kohlrabi under organic and conventional cropping

Although crops produced in organic cultivation are considered to be better for health and often have better sensory characteristic than conventionally produced foodstuffs, the influence of cropping practice on phytochemicals content and healing properties of plant-based food still needs clarification. This study compared nutrient quality and biological activity of Brassica oleracea vegetables grown under organic and conventional production systems. Total glucosinolate, phenolics and flavonoids concentrations, together with antioxidant capacity of vegetable juices against 1,1-diphenyl-2-picryl-hydrazyl radicals (DPPH), 2,2’-azino-bis(3-ethylbenzthiazoline-6-sulfonic acid) and cupric ion reagent were estimated. Antimicrobial activity against bacteria and fungi, together with antiproliferative activity in tumour cell lines were investigated. Organic cropping increased total glucosinolates concentration in broccoli (B. oleracea L., var. italica Plenck) and cauliflower (B. oleracea L. var. botrytis l.c.). Higher total flavonoids concentration was found in all conventionally grown vegetables. Juices of conventionally grown broccoli and cauliflower were more effective antioxidants, antimicrobials and cancer chemopreventive agents than their organically grown counterparts and those from kohlrabi (B. oleracea L. var. gongylodes l.c). Cropping system and vegetable variety together affected chemical composition and biological activity of B. oleracea vegetables. Thus, the combination of both factors must be considered when producing vegetables with health-promoting properties.