In vitro degradation of 10 mono‐ and sesquiterpenes of plant origin by caprine rumen micro‐organisms

The extent of disappearance of 10 mono- and sesquiterpenes in presence of mixed rumen micro-organisms has been measured in 24-h batch cultures. The molecules that were tested are frequently found in the plants consumed by ruminants in highland pastures (limonene, β-myrcene, β-ocimene, α-pinene, sabinene, γ-terpinene and thymol) or are potential markers of the diet (camphene, β-caryophyllene and α-copaene). All terpenes were tested at 2 µL mL−1, except α-copaene and thymol, which were tested at 0.9 µL mL−1 and 2 mg mL−1, respectively. Camphene and thymol were not degraded to a significant extent. The disappearance of part of β-caryophyllene, (−)-limonene and γ-terpinene could not be attributed to the direct action of rumen micro-organisms but rather than to an effect of the extracellular medium. In contrast, a third group of one sesquiterpene (α-copaene) and four monoterpenes (myrcene, β-ocimene, α-pinene and sabinene) was extensively degraded by rumen micro-organisms, at rates of 1.6, 4.5, 3.5, 4.8 and 5.4 µmol mL−1 inoculum day−1, respectively. The preliminary exposure of rumen micro-organisms to a specific blend of essential oils compounds, containing mainly thymol, guajacol and limonene, increased the extent of disappearance of γ-terpinene only. Copyright © 2007 Society of Chemical Industry