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. 2021 Aug 22;26(16):5081.
doi: 10.3390/molecules26165081.

Olive Trees By-Products as Sources of Bioactive and Other Industrially Useful Compounds: A Systematic Review

Valentina Lo Giudice  1 , Immacolata Faraone  2   3 , Maria Roberta Bruno  1 , Maria Ponticelli  2 , Fabiana Labanca  2 , Donatella Bisaccia  4 , Carmine Massarelli  4 , Luigi Milella  2 , Luigi Todaro  1
Affiliations

Olive Trees By-Products as Sources of Bioactive and Other Industrially Useful Compounds: A Systematic Review

Valentina Lo Giudice et al. Molecules. .

Abstract

The need to produce an ever-increasing quantity of material products and food resulting from the planet globalization process has contributed to the spread of modern agriculture based on a linear production resulting in the generation of tons of waste. This huge amount of waste is generally accumulated in landfills, causing different environmental problems. Hence, researchers moved on to study the processes used to recover agro-industrial by-products within a circular and sustainable bio-economy concept. A systematic quest on Scopus and PubMed databases was performed to identify the data available to date on recycling agro-industrial by-products of Olea europaea L. This systematic review summarizes the knowledge regarding the use of olive trees by-products for producing animal feed, biocomposites, bioethanol, cellulose pulp, activated carbon, and as a fuel source for energy production. Furthermore, the data regarding the potential biological activity of extracts from olive roots, wood, bark, and pruning were analyzed. Olive trees by-products are, indeed, rich in molecules with antioxidant, antimicrobial, cardioprotective, and anticancer activity, representing a promising candidate for treat several human diseases.

Keywords: bioactivity; circular economy; specialized metabolites.

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Conflict of interest statement

The authors declare no conflict of interest.

Figures

Figure 1
Figure 1
Flow diagram of the systematic review literature search results based on PRISMA statement.
Figure 2
Figure 2
Distribution of articles by country. Spain, 57.33%; Tunisia, 14.67%; Italy, 5.33%; India, Iran, Arabia, Algeria, Turkey, and Syria, 2.67%; Greece, Pakistan, Tanzania, USA, Poland, 1.33%.
Figure 3
Figure 3
Distribution of studies by year of publication, focusing on industrial uses (orange) and biological activity (blue).
Figure 4
Figure 4
The assessment of bias risk is based on a checklist adapted from the Cochrane Handbook for Systematic Reviews of Interventions [17] and Collaboration for Environmental Evidence (CEE) Guidelines and Standards for Evidence Synthesis in Environmental Management, in conformance to ROSES reporting standards [18,19]. The studies regarding the different biological activities and the industrial uses have been classified into high (red), medium (orange), and low (blue) risks of bias.
Figure 5
Figure 5
Graphical representation of O. europaea agro-industrial by-product biological activity. Extracts from olive roots, pruning, wood, and bark, showed antioxidant, antimicrobial, anti-platelet aggregation, and anticancer activities. These activities are related to the high content in bioactive compounds like oleuropein, hydroxytyrosol, and (+)-cycloolivil.
Figure 6
Figure 6
Graphical representation of O. europaea agro-industrial by-product recycling processes.
See this image and copyright information in PMC

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