Polyphenolic composition, enzyme inhibitory effects ex-vivo and in-vivo studies on two Brassicaceae of north-central Italy

Abstract

In this study, three different extracts (soxhlet, microwave and decoction) from two species of broccoli: Brassica oleracea L. convar. Italica botrytis (L.) Alef. var. cymosa Duch. (Broccolo Fiolaro) and Brassica oleracea acephala L. convar. acephala (DC.) Alef. var. sabellica L. (Cavolo Nero), which are commonly spread in north-central Italy, were tested for their enzyme inhibitory effects. Enzyme inhibitory effects were investigated against cholinesterases, tyrosinase, α-amylase and α-glucosidase. The soxhlet extracts had the highest inhibitory AChE effects with 1.08 mgGALAE/g (in Cavolo Nero) and 0.90 mgGALAE/g (in Broccolo Fiolaro). The significant tyrosinase inhibitory effect was observed in the soxhlet extract of Cavolo Nero with 11.93 mgKAE/g. In addition, we evaluated the antioxidant activity of Broccolo Fiolaro and Cavolo Nero on lipopolysaccharide (LPS)-stimulated bladder, kidney and liver specimens, ex vivo. We observed a significant reduction of both nitrite and malondialdehyde (MDA) following treatment that indicates a significant inhibitory effect on oxidative/nitrosative stress and lipoperoxidation, respectively. Additionally, the blunting effect induced by extracts on LPS-induced lactate dehydrogenase (LDH) activity further support a protective effect by both Broccolo Fiolaro and Cavolo Nero in bladder, kidney and liver. HPLC analysis revealed that catechin, epicatechin, vanillic and 3-hydroxy benzoic acids were the major components. The phenolic components may contribute to the observed enzyme inhibitory effects. in vivo tests also demonstrated that the extracts decreased the biochemical parameters in diabetic rats. Particularly, we observed the reduction of plasma glucose levels, urea and total cholesterol following oral administration, with the higher inhibitory effects exerted by Broccolo Fiolaro compared to Cavolo Nero. Overall, our results could provide new insights on the use of these Broccoli species not only as foods but also as functional and nutraceutical supplements.

Keywords: Brassica oleracea L.; Broccolo Fiolaro di Creazzo; Cavolo Nero; Enzyme inhibition; Extractions; HPLC-PDA.