Biologically active compounds available in Ceratonia siliqua L. grown in contrasting soils under Mediterranean climate

Abstract

Abstract The aim of this work was to understand how two different soil types (calcareous - C and non-calcareous soils - NC) affect carob tree nutritional performance and bioactive compounds present in the pulp of the pod. Two orchards were selected in two separately separate locations: in soil C, trees were grown under calcareous conditions, with high percentage of active lime (>9%) and a soil pH of 8.1 and in soil NC, no carbonates were present and soil pH was 6.6. Leaf mineral composition, total leaf chlorophyll and several bioactive compounds were monitored in trees of the cv. ‘Mulata’ during three years and covering two seasons in both orchards. Unripe and ripe pods were separately analyzed. Trees in the NC site were smaller and less vigorous but presented higher leaf chlorophyll, and higher N, Mg, Zn, Fe and Mn in leaves, than trees of the C site. In the latter, only Ca and K were slightly higher. Unripe pods in both orchards showed significantly higher polyphenols content and high anti-oxidant activity (expressed as DPPH). Condensed tannins content was related to leaf mineral composition (N, Zn and Mn) but among these, Mn was the most important and its accumulation in leaves is a good indicator of anti-oxidant activity. Condensed tannins content was higher in unripe pods of trees in the NC site.