# Antimicrobial and Odour Qualities of Alkylpyrazines Occurring in Chocolate and Cocoa Products
## 3 Antimicrobial Activity of Pyrazines
### Antifungal and Antioomycete Activity  
Multiple studies revealed how pyrazine compounds had potent antifungal and antioomycete properties. The antagonism of those substances against osmolvetes and funguses that are harmful to plants is particularly prevalent. [PERSON] et al. [43] discovered the properties of pyrazine derivatives produced by plant endophyte Pseudomonas putida BP25--2: 2,5-dimethylpyrazine; 2-methylpyrazine; 2-ethyl-5-methylpyrazine; and 2-ethyl-3,6-dimethylpyrazine. Those volatile organic compounds (VOCs) performed compelling inhibitory activity against oomycete pathogens, Phytophthoraora capsici and Pythium myri-otylum; fungal pathogens, Rhizotonia solani, Colletotrichum gloeosporoides, Athelia rolfsii, Gibberella moniliformis and Magnaporthe oryzae; bacterial pathogen, Ralstonia pseudosolanacearum and plant parasitic nematode, Radopholus similis. 2-Ethyl-3,6-dimethylpyrazine was the compound with the most impressive performance against the majority of the pathogens and its EC50 (half maximal effective concentration) values varied between 13 and 145.8 ug/mL. 2-Ethyl-5-methylpyrazine and 2-ethyl-3,6-dimethylpyrazine fully restrained bacterial growth on a CPG agar at 339 and 509 ug/mL, respectively. Against Phytophthora rot on Black pepper shoot cuttings 2,5-dimethylpyrazine, 2-ethyl-5-methylpyrazine and 2-ethyl-3,6-dimethyl-pyrazine performed a contraction of contamination at 21 ug/mL, and 2-methylpyrazine at 42 ug/mL, with no signals of toxicity. Pyrazine derivatives including 2,5-dimethylpyrazine, 2-ethyl-3-methylpyrazine, 2-ethylpyrazine and 2-methyl pyrazine were shown by [PERSON] et al. [50] in their study on  
Figure 3: Mechanism of antitubercular activity of Pyrazinamide. Black pepper root entophytic Bacillus megaterium BP17 volatiles as effective antifungal and antioomycete chemicals. At concentrations of 504 g/mL for 2,5-dimethylpyrazine, 2-ethyl-3-methylpyrazine and 2-ethylpyrazine and 672 g/mL for 2-methylpyrazine, trials on the oomycete Phytophthora capsaicin revealed the full suppression of mycelial growth. The same potent inhibition of the fungus Magnaporthe oryzae's mycelial growth was seen: total inhibition for 2-ethyl-3-methylpyrazine at 168 g/mL, total inhibition for 2-ethylpyrazine and 2-methylpyrazine at 672 g/mL and 73.68% inhibition for 2,5-dimethylpyrazine at 672 g/mL. 2-Methylpyrazine was found to be a major volatile product synthesized by four bacterial strains of Bacillus spp. and performed a strong inhibition of the Colletotrichum gloeosporoides in the concentration of 100 \(\upmu\)L/L, inhibiting mycelial growth from 8.59 cm to 1.45 cm. C. gloeosporoides is one of the most common Colletotrichum fungal plant pathogens which provokes plant disease anthracose [49]. It was found that 2,5-dimethylpyrazine, trimethylpyrazine and tetramethylpyrazine as one of the products of the metabolism of cyanogenic Pseudomonas strains are active against oomycete Phytophthora infestans, which is considered one of the harshest and widespread pathogens of Solanum tuberosum [53]. [PERSON] et al. [54] found that despite not showing a decrease in the germination of fungal spores, pyrazine and 2,5-dimethylpyrazine are formed in fungistatic soils and may contribute to the process of soil volatile fungistatication through synergistic actions. Pyrazine derivatives were identified as the primary components of bacterial metabolism in the gas chromatography-mass spectrometry (GC-MS) study of the volatiles of two bacterial strains, Bacillus pumilus and _Paenibacillus_ species. Bacillus pumilus mostly produced 2,5-dimethylpyrazine, with lower amounts of 2-ethyl-3,5-dimethylpyrazine. The _Paenibacillus_ species metabolic products contained the highest quantities of not recognized pyrazine derivative and 2,6-bis(2-methylpropyl)-pyrazine.