In recent years, significant progress has been made in
transdermal
drug delivery systems, but there is still a search for enhancers that
can improve the absorption of active substances through thestratum corneum. Although permeation enhancers have been
described in the scientific literature, the use of naturally occurring
substances in this role is still of particular interest, because they
can offer a high level of safety of use, with a low risk of skin irritation,
and high efficiency. In addition, these ingredients are biodegradable,
easily available, and widely accepted by consumers due to the growing
trust in natural compounds. This article provides information on the
role of naturally derived compounds in transdermal drug delivery systems
that help them penetrate the skin. The work focuses on the components
found in thestratum corneumsuch as sterols, ceramides,
oleic acid, and urea. Penetration enhancers found in nature, mainly
in plants, such as terpenes, polysaccharides, and fatty acids have
also been described. The mechanism of action of permeation enhancers
in thestratum corneumis discussed, and information
on the methods of assessing their penetration efficiency is provided.
Our review mainly covers original papers from 2017 to 2022, supplemented
with review papers, and then older publications used to supplement
or verify the data. The use of natural penetration enhancers has been
shown to increase the transport of active ingredients through thestratum corneumand can compete with synthetic counterparts.