Tylvalosin, a derivative of tylosin's component A, differs crucially in the introduction of an isovaleryl group. This structure imparts lipophilicity, enabling it to easily cross cell membranes and accumulate efficiently in the cytoplasm. In contrast, tylosin has difficulty entering cells and, therefore, lacks antiviral efficacy.
In addition, tylosin's metabolite, 3-O-acetyltylosin, also exhibits potent antibacterial activity. However, tylosin's metabolites lack antibacterial activity.
