Screening of antioxidant phenolic compounds produced by in vitro shoots of Brassica oleracea L. var. costata DC

Brassica oleracea L. var. costata DC, commonly known as tronchuda cabbage, is a unique vegetable, very important for Portuguese horticulture, owing to its excellent adaptation to a wide range of climatic conditions and good integration in the traditional small farming cropping systems. Among phytochemicals possessing antioxidant capacity, phenolic compounds are one of the most important groups. The accumulation of phenolics by in vitro cultures is known to be influenced by hormonal supplementation. As consequence, the phenolic composition can be modulated in order to achieve the best antioxidative properties. The phenolic compounds produced by in vitro shoots of B. oleracea var. costata were screened by HPLC-DAD-MS/MS. Thirty seven compounds were characterized, which included chlorogenic acids, flavonoids (the majority of them were hydroxycinnamic acid esters of kaempferol and quercetin glycosides) and hydroxycinnamic acyl glycosides (with predominance of synapoyl gentiobiosides). The antioxidant capacity of the shoots was assessed against DPPH radical and two reactive oxygen species (superoxide radical and hypochlorous acid). A strong concentration-dependent antioxidative capacity was verified in the DPPH and superoxide radicals assays, but a reduced effect was noticed against hypochlorous acid. The results obtained indicate that the production of B. oleracea var. costata shoots can become important in the obtainment of a noticeable dietary source of compounds with health protective potential.

Acknowledgements: Fundação Calouste Gulbenkian, Patrícia Valentão. Fundação para a Ciência e a Tecnologia (PTDC/AGR-AAM/64150/2006), David M. Pereira.