Content of the Saponin Protodioscin in Brachiaria spp. from the Eastern Plains of Colombia

Abstract

Protodioscin is used as a marker of saponin content that could cause hepatotoxicity in ruminants. In Brachiaria spp. from two regions of the Colombian Eastern Plains (east mountain range of the Andean-"piedemonte" and Ariari River Valley) were determined this metabolite at 14 and 28 days post-cutting under different climatic conditions. No protodioscin was detected in B. dictyoneura or B. humidicola. In B. brizantha, B. decumbens and B. ruziziensis x B. decumbens x B. brizantha (hybrid), protodioscin content corresponded to an interaction between species, post-cutting time and season. Concentrations ≥1% (minimum toxic level) were recorded in B. decumbens and the hybrid, and to a lesser extent in B. brizantha. The concentration of protodioscin was higher at 28 days, when the pastures are suitable for consumption. B. brizantha accumulated the lowest saponin concentration, whereas the hybrid had the highest levels, particularly in the "piedemonte" and during drought (3.37%). Dry season favored the protodioscin concentration in B. decumbens (in river valley) and in the hybrid (in "piedemonte"). In the latter, there was a positive correlation with temperature and a negative with humidity, which are typical characteristics of dry periods. This is the first report of protodioscin content in the hybrid.

Keywords: Brachiaria spp.; Colombian eastern plains; protodioscin; saponin.

Figure 1

Protodioscin concentration in Brachiaria spp. (based on dry matter) from “piedemonte” in Colombian Eastern Plains; at 14 days (A) and 28 days (B) post-cutting. Hybrid: B. ruziziensis x B. decumbens x B. brizantha. Lowercase letters indicate statistical differences between species of the same post-cutting time at the same season. Capital letters indicate statistical differences in the same species of the same post-cutting time between seasons. n = 3. p < 0.05.

Figure 2

Protodioscin concentration in Brachiaria spp. (based on dry matter) from Ariari river valley in Colombian Eastern Plains; at 14 days (A) and 28 days (B) post-cutting. Hybrid: B. ruziziensis x B. decumbens x B. brizantha. Lowercase letters indicate statistical differences between species of the same post-cutting time at the same season. Capital letters indicate statistical differences in the same species of the same post-cutting time between seasons. n = 3. p < 0.05.

Figure 3

Linear correlation between the environmental parameters temperature (A) and relative humidity (B) and protodioscin concentration (based on dry matter) for the hybrid (B. ruzizienzis x B. decumbens x B. brizantha).

Figure 4

Precipitation in “piedemonte” and Ariari river valley during the sampling period. Points indicate the moment when the pastures were collected.

Figure 5

Chromatograms of protodioscin. (A) Standard solution of 500 μg/mL. (B) Extract of a B. decumbens sample containing protodioscin at a concentration equivalent to 2.22% in the dried grass sample.