# Antimicrobial and Odour Qualities of Alkylpyrazines Occurring in Chocolate and Cocoa Products
## 3 Antimicrobial Activity of Pyrazines
### Antibacterial Activity  
Tetramethylpyrazine (TMP), as an illustrative example, revealed itself in studies as an active antibacterial agent for various strains of bacteria. TMP, also known as ligustrazine, is a bioactive compound that has been known for its antibacterial properties in Ancient Chinese medicine [45; 46]. [PERSON] et al. [47] studied the TMP effect on gut opportunistic bacteria such as Clostridium perfingens, Escherichia coli, gram-negative bacteria and Salmonella of broilers with necrotic enteritis (NE). The populations of gut opportunistic bacteria expanded in infected broilers (\(p<0.05\)), which was then diminished by the introduction of TMP (\(p<0.05\)) into the feeding scheme. Compelling linear and quadratic trends of the implication of TMP on the growth of Salmonella (\(p=0.001\)) and gram-negative bacteria (\(p=0.000\)) were spotted. Although the level of bacterial contamination was below the control, TMP also weakened the enterotoxin markers, including the level of endotoxin and diamine oxidase, which further indicated its potent antibacterial properties. They additionally detected the antioxidative and anti-inflammatory properties of TMP by reducing inflammatory factors such as tumour necrosis factor-\(\alpha\) (TNF-\(\alpha\)), Interleukin-18 (IL-18) and Interleukin-6 (IL-6); reducing oxidative products such as malondialdehydedehyde (MDA) and protein carbonyl (PCO); increasing the level of antioxidation factors; and reducing glutathione (r-GSH), glutathione peroxidase (GSH-Px) and superoxide dismutase (SOD), which could serve as an additional beneficial impact on contaminated organisms. [PERSON] et al. [48] studied the influence of TMP addition to those infected with Salmonella Typhimurium. They found a decreasing effect on Salmonella load in the ileum, spleen, mesenteric lymphoid follicles and skin, compared with the negative control (\(p<0.05\)), and S. Typhimurium was challenged (\(p<0.01\)) by 11.4% to 23.6% and 13.8% to 45.8%. TMP was found to be active against Campylobacter jejuni load in rabbits [46]. C. jejuni is a fast-spreading bacteria, which could infect humans by consuming contaminated food, particularly poultry. Treatments with different doses of TMP showed a partial inhibition of C. jejuni in rabbit caecal content, skin, liver and spleen. An increase in the dose of TMP provoked a linear (\(p<0.001\)) and quadratic (\(p\leq 0.026\)) reduction in C. jejuni loads in the liver and spleen, which may be interpreted as affecting the influence of TMP on bacterial transmission. It was discovered that a dietary addition of TMP also activates the production of endogenous antimicrobial peptides in the caecum (NP4 = defencing neutrophil peptide 4, MCP2 = macrophage cationic peptide 2, LGALS3 = galectin 3, CAMP = cathelicidin antimicrobial peptide) and skin (SEM = standard error of the mean, NP4, MCP2, LGALS3). The best results presented CAMP with a linear trend (\(p<0.001\)) and reached the control level along with LGALS3 with a linear trend (\(p<0.001\)) in the caecum. It was suggested by [PERSON] et al. [45] that TMP and other pyrazine compounds provide an antibacterial effect by purifying reactive oxygen species, which act as a suppressor of bacterial growth and inflammation. Pyrazine compounds could be exploited as antimicrobial agents against plant infections in addition to being antibacterial agents for humans and animals. Recently, volatile organic compounds (VOCs) produced by microorganisms have been evaluated as a new way of fighting plant microbial contamination [49]. 2,3-Dimethylpyrazine and 2,5-dimethylpyrazine antibacterial efficacy was tested on 10\({}^{3}\)_E. coli_ cells with 0.3%, 0.6% and 1.2% dosages incubated for 2, 4 and 6 h. Even though 2,3-dimethyl-pyrazine caused no reduction in bacterial colonies, 2,5-dimethylpyrazine showed a great decrease in _E. coli_ cell concentration. Higher doses applied and a longer incubation time boosted the effect.