Re: How do antiseptics kill bacteria?

Thymol belongs to a group of compounds called phenolics. This group is so-called beacuse all of its members are based on the group's simplest chemical, phenol. Phenol's antiseptic properties were first brought to attention by Lister (he called it carbolic acid), who is now immortalized by the product he first concocted, Listerine.

The problem with phenol is that it is very caustic and, as every molecular biologist knows, has a very strong and displeasing odor. So microbiologist looked for similar chemicals that were less caustic yet retained the antiseptic properties of phenol.

Phenolics are very strong denaturants (i.e.make inactive) of proteins. This may be do to some oxidative properties of phenolics. In fact, the more oxidized a phenolic compound is, the more potent it generally becomes.

But the main antiseptic effect of phenolics like thymol is due to the disruption of cellular membranes. Phenolics are lipophilic compounds. That means they like lipid molecules like those found in cellular membranes. To the best of my knowledge, the exact chemistry behind the disruption of the membrane is not well understood. But phenolics essentially punch holes in the membrane allowing essential ions and chemicals to leak out of the cell. The holes in the membrane may also allow the phenolic compounds to more easily enter the cell where they can denature proteins and inhibit a variety of essential cellular processes.