Secondary metabolites (SMs), usually of complex structure and low
molecular weight, have remarkable biological activities and, unlike the primary
metabolites, are presented in low concentrations and in certain groups of plants.
These, in turn, arouse great interest, not only for the biological activities exerted by
plants in response to environmental stimuli, but also for the immense pharmacological
activity they possess. Many are of commercial importance, not only in the
pharmaceutical area, but also in the food, agronomy, perfumery, and other important
sectors. In general, secondary metabolites are natural compounds produced in plants
with the main objective of protection against abiotic and biotic stresses, besides
having important nutritional and pharmacological aspects in human nutrition, they
are also sources of aromatic additives, dyes, antioxidants and exert numerous
functions. There are many ways to extract these compounds, but green chemistry
can generate economic benefits in industrial chemical processes, such as reducing
the need for investments in storage and effluent treatment, as well as the payment of
compensation for any environmental damage. In addition, the use of bioresidues as
promising sources of secondary metabolites is a promising way to promote the
circular economy and take advantage of these by-products through bioactive compounds
and their application as additives in new food sources. Currently one of the
challenges is to produce sources of secondary metabolites from domesticated plants,
since these have differences from wild ones, and the domestication process could
preserve defense traits, such as changing the significantly, in addition to
domestication-related climate changes, which may also attribute other characteristics
to the secondary metabolites. Moreover, another interesting biotechnology applied
to obtain large-scale SMs naturally produced by fungi is heterologous expression,
which consists in the transcription of one or more genes from the cluster data gene of the fungi producing the target compound in a secondary host, which in most studies
are yeasts or filamentous fungi.
The use of these compounds in turn must be in force within the parameters
allowed by legislation for food incorporation and in the industry in general, since
they differ according to the sources, uses, toxicological levels, and the regulations
regarding their certifications. However, secondary metabolites emerge as a promising
source for new opportunities of application, emphasizing their potential to act as
strong and natural additives for several industrial purposes.
The authors are grateful to the Foundation for Science and Technology (FCT,
Portugal) for financial support through national funds FCT/MCTES to CIMO (UIDB/00690/2020).
L. Barros thanks the national funding by FCT through the institutional scientific employment
program-contract for her contract, while S. A. Heleno thanks FCT through the individual scientific
employment program-contracts (CEECIND/03040/2017). I. Oliveira and B. Albuquerque also
thank FCT for their PhD grants (BD/06017/2020 and BD/136370/2018, respectively).
