The time of existence of ozone in gaseous form in the presence of biological systems is extremely short because these substrates are rich in easily oxidizable substances.

The double bonds present react very quickly and therefore the systemic and local effects of ozone are to be found in the reaction of ozone itself, i.e. in its metabolites.

These prevent breaking of the unsaturated fatty acid chains; they are shorter and have a smaller molecular weight so they can penetrate more easily the cellular membrane exerting their action inside the cell itself.

Penetration ability and absence of toxicity are justified by the similarity of these metabolites with lipid peroxides endogenous to living biological systems.

The instability of ozone is what drove researchers to create the conditions needed to store gas in a biological tank, so that it could be used at the required moment.

The affinity of the gas to unsaturated fatty acids has been employed by absorbing and bonding ozone with vegetable oils which, under suitable reaction conditions, give rise to the so called ozonides, compounds that are able to store oxygen in a readily transferable form.

Figure 1 shows the general reaction of ozonide formation: the ozone molecule electrophilically adds the double bond of the fatty acid yielding a compound called primary ozonide.

This very unstable intermediate decomposes rapidly through heterolysis of the O-O and C-C bond to form a carbonylic compound and zwitterion.

In the absence of reactive solvents, the carbonylic compound is then added rapidly to form normal ozonide, while in the presence of water or other reactive solvents it produces hydroperoxides and peroxides