The objective was to study the effect of the typical plant extracts of the Brazilian Cerrado on in vitro rumen microbial fermentation under a high concentrate diet. Two separate trials were conducted to evaluate 4 doses (0, 30, 300 and 3,000 mg/L) of trunk oil from Copaifera langsdorffii (Trial 1; 21.3% β-caryophyllene – essential oil) and fruit oil from Pterodon emarginatus (Trial 2; 5.3% β-caryophyllene – essential oil). The trials were analyzed as a randomized block design with 5 repetitions, treating incubation as the blocking factor. Treatments were evaluated using a TE-150 incubator ((Tecnal) in a batch culture of rumen fluid with a 10:90 forage:concentrate diet (15% crude protein, 20% neutral detergent fiber) incubated using filter bags of non-woven textile for 2, 4, 8, 12, 24, and 48 h (triplicates each time) to fit the disappearance of dry matter (DM). volatile fatty acids (VFA), pH, and ammonia nitrogen (NH₃-N) were evaluated after 48 h of incubation. The inclusion of 3,000 mg/L of oil C. langsdorffi reduced (84.7 vs 63.8%) the potential degradability (a + b) of DM and tended to decrease (P < 0.10) the VFA (76.6 vs 60.6 mM), acetate (52.27 vs 42.11 mM) and NH₃-N (119.12 vs. 101.47 mg/dL) concentration. Acetate:propionate ratio (C₂:C₃) was significantly reduced (3.55 vs 2.81) at a dose 300 mg/L of C. langsdorffi. The proportion of isovalerate was affected (P < 0.05) at a dose 300 (1.93 vs 1.88 mM) and 3,000 mg/L (1.9 vs 1.6mM). No effect (P > 0.10) of P. emarginatus on the kinetics of disappearance of rumen DM was detected. However, the addition of 30 and 300 mg/L of P. emarginatus oil increased (P < 0.05) the total VFA concentration by an average of 28.3%. The 3,000 mg/L dose significantly decreased C2:C3 ratio (3.77 vs 2.76 mM) due to a 27.9% reduction in the proportion of acetate. The results indicated that Cerrado plant oil are potential modifiers of rumen fermentation under a high concentrate diet.