Phenolic compounds are probably the most explored natural compounds due to their potential health benefits as demonstrated in a number of studies. Generic terms 'phenolic compounds', 'phenolics' or 'polyphenolics' refer to more than 8,000 compounds found in the plant kingdom and possessing at least an aromatic ring with one or more hydroxyl substituents, including functional derivatives like esters, methyl ethers, and glycosides. The basic structure of a phenolic compound comprises of an aromatic ring with one or more hydroxyl (–OH) groups. However, phenolic compounds found in Nature are structurally diverse from simple phenolic molecules to complex polymerized compounds. Therefore, the antimicrobial properties of phenolics can be attributed to the presence of –OH groups in their structure. The number and position of double bonds in the structure have also been reported to play a major role in determining the relative toxicity of phenolics against microorganisms.