Could squalene be an added value to use olive by-products?

Squalene (SQ) is an intermediate hydrocarbon in the biosynthesis of phytosterols and terpenes in plants. It is widely used for applications such as skin moisturizers, vaccines, or in carriers for active lipophilic molecules. It has commonly been obtained from sharks, but restrictions on their use have created a need to find alternative sources. We present a review of studies concerning SQ in olive groves to characterize its content and to provide new aspects that may increase the circular economy of the olive tree. There is a large variation in SQ content in virgin olive oil due to cultivars and agronomic issues such as region, climate, types of soil, crop practices, and harvest date. Cultivars with the highest SQ content in their virgin olive oil were 'Nocellara de Belice', 'Drobnica', 'Souri', and 'Oblica'. An interaction between cultivar and aspects such as irrigation practices or agricultural season is frequently observed. Likewise, the production of high SQ content needs precise control of fruit maturation. Leaves represent an interesting source, if its extraction and yield compensate for the expenses of their disposal. Supercritical carbon dioxide extraction from olive oil deodorizer distillates offers an opportunity to obtain high-purity SQ from this derivative. Exploiting SQ obtained from olive groves for the pharmaceutical or cosmetic industries poses new challenges and opportunities to add value and recycle by-products.