Effect of climatic and sulphur fertilisation conditions, on phenolic compounds and vitamin C, in the inflorescences of eight broccoli cultivars

Abstract

Flavonoids, hydroxycinnamoyl derivatives (sinapic and ferulic acid derivatives+caffeoyl-quinic acid derivatives) and vitamin C were quantified by HPLC-MS in five commercial and three experimental cultivars from freshly harvested broccoli inflorescences ( Brassica oleracea L. var. italica). In order to identify differences due to genetic and agronomic factors, the broccoli cultivars were grown under different climatic and agronomic conditions, i.e. early (winter) and late (spring) seasons with poor (15 kg/ha) and rich (150 kg/ha) sulphur fertilisation. The predominant sinapic and ferulic acid derivatives in all broccoli cultivars were 1,2-diferuloylgentiobiose, 1,2,2'-trisinapoylgentiobiose and 1,2'-disinapoyl-2-feruloylgentiobiose. In addition, the compounds 1,2-diferuloylgentiobiose, 1-sinapoyl-2,2'-diferuloylgentiobiose and 1,2,2'-triferuloylgentiobiose were identified in broccoli inflorescences for the first time. Extreme agronomic and environmental conditions (late season and rich sulphur fertilisation which could induce different stress situations on the plant) enhanced the phenolic content. Thus, total flavonoids showed the highest content, followed by total sinapic and feruloyl acid derivatives and total caffeoyl-quinic acid derivatives. In general, cultivars grown under rich fertilisation and late season conditions showed higher vitamin C content than those grown under the poor and early ones. Finally, results showed that commercial cultivars rendered higher amounts of phenolic compounds and vitamin C than the experimental ones.