Methane reduction by plant pigments and antioxidants in rumen fluid involves modifications, e.g. hydrogenatioor degradation of the active compoundsn,

Methane is a major greenhouse gas, and ruminants cause about a quarter of all anthropogenic methane emissions. The objective of this study was to testplant secondary products in terms of their effects on methane production, and to follow active compounds analytically during incubation. In a simplifi ed model of ruminal methane production, a glycerol tripolylactate served as a central metabolites-generating and hydrogen-releasing substrate for rumen prokaryotes. The experimental additives, tested for their interfering potential with methane production, comprised bilberry fruit extract, tomato paste, paprika powder, grape seed extract, turmeric powder, curcumin, catechin, ferulic acid, ferulic acid ethyl ester and resveratrol. Being an unsaturated compound, fumarate, a competing electron acceptor to methane precursors, served as a well-described methane-reducing compound among the experimental additives in the in vitro tests. Methanemitigating effi ciencies were calculated by subtraction of the methane quantity produced in fl asks with the interfering additives from the quantity measured without any additive. Grape seed extract, bilberry fruit extract, turmeric powder, ferulic acid, catechin, and resveratrol reduced the production of methane in vitro. Grape seed extract, bilberry fruit extract, catechin, and resveratrol decreased methane formation to a higher extent than fumarate when added at comparable concentrations. Analysis of the secondary compounds in the assays by means of HPLC and revealed a considerably and in most cases significant (p