It is known that plant secondary metabolites are bioactive phytochemicals, both through important vital roles which have the plant producing it, and through their effects on human and animal body at its exogenous application. Different phytochemical compounds, representatives of different phytochemicals classes exogenously applied in different systems shows stimulants plant growth, antioxidants, cells membranoprotectives, tissues regenerators and other activities. These manifestations of secondary metabolites plant bioactivity inspired the research described in this paper on stimulating activity of methanogenic microorganisms in the biochemical anaerobic fermentation processes on organic substrates with emission of biogas as an energy source. Were tested, in special conditions of a laboratory anaerobic digester (Covaliov V., Nenno V. and coauthors design) [1], biologically active substances from different phytochemicals classes: saponins, flavonoids, tannins, alkaloids, steroids, cumarins etc. A manifest intensification of anaerobic fermentation process occurred with the application of gypsoside (triterpenoid saponin), sclareol (bicyclic diterpenoid) and squalene (acyclic triterpenoid) as fermentation phytostimulators. As a substrate was used the mixture of pulp obtained after alcohol distillation and animal manure in weight ratio 3:1. The concentrations of the test compounds ranged from 10-3 - 10-5% by weight of the substrate. It is evident (Table 1) that addition of these three compounds in the reaction mixture increase biogas emission over a period of 220 hours by two times compared with control test - without addition of phytostimulator. Table 1. Emission dynamics and total biogas volume (ml) produced under the experiment conditionstabelIt is known that plant secondary metabolites are bioactive phytochemicals, both through important vital roles which have the plant producing it, and through their effects on human and animal body at its exogenous application. Different phytochemical compounds, representatives of different phytochemicals classes exogenously applied in different systems shows stimulants plant growth, antioxidants, cells membranoprotectives, tissues regenerators and other activities. These manifestations of secondary metabolites plant bioactivity inspired the research described in this paper on stimulating activity of methanogenic microorganisms in the biochemical anaerobic fermentation processes on organic substrates with emission of biogas as an energy source. Were tested, in special conditions of a laboratory anaerobic digester (Covaliov V., Nenno V. and coauthors design) [1], biologically active substances from different phytochemicals classes: saponins, flavonoids, tannins, alkaloids, steroids, cumarins etc. A manifest intensification of anaerobic fermentation process occurred with the application of gypsoside (triterpenoid saponin), sclareol (bicyclic diterpenoid) and squalene (acyclic triterpenoid) as fermentation phytostimulators. As a substrate was used the mixture of pulp obtained after alcohol distillation and animal manure in weight ratio 3:1. The concentrations of the test compounds ranged from 10-3 - 10-5% by weight of the substrate. It is evident (Table 1) that addition of these three compounds in the reaction mixture increase biogas emission over a period of 220 hours by two times compared with control test - without addition of phytostimulator. Table 1. Emission dynamics and total biogas volume (ml) produced under the experiment conditions