Abstract

BACKGROUND: Although secondary metabolites have often been studied considering their primary role as plant-defensive and their effect on consumers detrimental, their effects are usually dose-dependent, so it is important to consider their content at all phenological phases and in different plant organs. In this study the content of total phenolics (TotP), non-tannic phenolics (NTP) and proanthocyanidins (PA) was determined in natural populations of pasture species at defined phenological phases and in different plant organs and also in pathogen-infected plants.
RESULTS: Variation in TotP, NTP and PA contentwas observed in all species, phenological phases and plant organs. Leaf blades were the organs with the highest content in all species. The content of all examined compounds increased in infected leaves, reaching themaximum when 20% of plant tissues were attacked and decreasing at higher infection levels.
CONCLUSION: Delphinidin was found as an appropriate standard related to the PA structure of each plant species. PA concentrations were always in the range considered beneficial for animals, not exceeding 60 g delphinidin equivalent kg⁻¹ dry matter. The Folin–Ciocalteu and butanol/HCl/Fe³⁺ assays remain the most practical methods for screening large numbers of different plant species for TotP and PA.

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