From biosynthetic versatility to applications in therapeutics, Andrade’s team has been travelling through marine and terrestrial organisms.
Over the last two decades, the group of Pharmacognosy from the Faculty of Pharmacy at the University of Porto, have been breaking ground on the characterisation of a wide variety of natural products obtained from terrestrial and marine sources. The biosynthetic versatility of more than 300 natural sources has been capitalised with the study of plants, algae, marine invertebrates and insects, that were shown to produce active metabolites displaying biological properties. In turn, these molecules may be translated into the development of drugs, nutraceuticals and supplements. The group has been pursuing the discovery of molecules with therapeutic potential, in particular for the treatment of diseases with an inflammatory background and unbalanced redox homeostasis.
Shedding light on uninvestigated natural sources and setting new applications for the well-known
The discovery of new chemical entities from natural sources has been historically driven by the biological activity observed in crude extracts, two-thirds of the drugs placed on the pharmaceutical market being either derived from natural products or structurally similar. The development of nutraceuticals and functional foods also requires the most complete characterisation of small-molecule metabolite profiles, not only to identify active constituents, but also to assure the identity, authenticity, quality and safety of natural matrices.
In addition to samples from terrestrial and marine Portuguese ecosystems, collaboration with various research groups from Brazil, Guinea-Bissau and Thailand puts the group in a strategic position to ensure a privileged access to a large collection of biological matrices, including previously uninvestigated plants, from biodiversity-rich ecosystems in four continents. The study of various edible or medicinal plant species has allowed to detail the richness and structural complexity of several molecules with therapeutic potential, namely alkaloids, sterols and phenolic constituents, such as flavonoids and phenolic acids, frequently related with the recorded biological activities.
Combining target-based and phenotypic approaches, marine organisms from Portuguese coastal waters have been found to be prolific sources to the identification of lead structures that can be used directly or as templates for the development of new drugs. Steroidal constituents from marine macroinvertebrates and phlorotannin extracts obtained from macroalgae were found to interfere with inflammatory pathways, foreseeing potential applications in the pharmaceutical and nutraceutical industries.
Marine organisms from Portuguese coastal waters as producers of anti-inflammatory leads
Secondary metabolites play crucial roles in the chemical ecology of their producing organisms, being intrinsically encoded to be biologically active. Natural products feature privileged drug-like patterns that have evolved as preferred ligand-protein binding motifs, often correlating translationally into applications with clinical significance. Consequently, it is not surprising that many of the anti-inflammatory drugs used in clinical practice derive from natural sources. However, not only the current anti-inflammatory arsenal remains limited and associated with severe cardiovascular and gastrointestinal complications, but also epidemiological data, evidences an increase on the incidence and prevalence of chronic conditions with low-grade inflammatory status.
Normal inflammation is self-limiting, but anomalous resolution and prolonged inflammation leads to chronic disorders, the highest incidences being observed in Europe. As such, the search for new anti-inflammatory drugs has been a current preoccupation, due to the need for effective drugs, with less adverse effects than those used nowadays. Aligned with this priority, the group have been actively enrolled on the discovery of naturally-sourced anti-inflammatory agents, based on the systematic investigation of both medicinal plants and marine organisms.
Ethnopharmacological approaches allowed identifying several native medicinal plants from Thai and Guinea-Bissauan flora as sources of known anti-inflammatory phenolics, but the most notable examples of active constituents that may successfully target inflammatory mediators have been found in marine organisms from the Portuguese coastal waters. Phlorotannin extracts from Fucales were found to act upon enzymatic and non-enzymatic inflammatory targets, reducing the levels of the pro-inflammatory mediator nitric oxide in cellular models of inflammation and exerting relevant inhibitory effects upon lipoxygenase. Based on the bioassay guided-fractionation of an extract obtained from the sea slug Aplysia depilans, isolation and characterisation of an anti-inflammatory steroidal endoperoxide calls for further preclinical development.
The active constituent is able to decrease cellular nitric oxide levels in macrophages through the downregulation of the Nos2 (inducible nitric oxide synthase, iNOS) gene, also inhibiting the LPS-induced expression of cyclooxygenase-2 (COX-2), interleukin 6, and tumor necrosis factor alpha (TNF-α) at both mRNA and protein levels. Relevant anti-inflammatory properties were also noted in cellular models upon exposure to the steroid ergosta-7,22-dien-3-ol, which was shown to occur in the echinoderm Marthasterias glacialis. The mechanism of action is characterised by the downregulation of COX-2, prevention of IκB-α degradation, as well as through the reduced expression of CHOP, a common marker of endoplasmic reticulum stress which has been increasingly implied in inflammatory processes. Such findings allow to work on a new paradigm in the treatment of inflammatory-related conditions, as these metabolites may have their medicinal chemistry developed from leads to new clinical drugs.
Delivery of functional ingredients with lipid-based nanocarriers
Many bioactives extracted from plants and marine sources have low bioavailability, deterring their ability to cross cellular barriers and reach the intracellular targets. To overcome these weaknesses and improve their biological fate, several delivery systems with functional properties have been formulated over the last few years. Recently, the group set a new line of research dealing with the formulation of lipid-based nanocarriers for the delivery of functional phytochemicals. Such nano-systems are characterised by an appropriate miscibility in both aqueous and lipid environments due to their amphipathic properties, enabling a finely tuned delivery of active constituents. Rutin nanoliposomes, supported by egg yolk phospholipids, were conveniently designed and characterised, providing a proof-of-concept on their utility to act on central nervous system targets. Standardised phenolic-rich extracts obtained from pennyroyal (Mentha pulegium) were also combined with egg yolk lipids in order to enhance the extract ability to inhibit MAO-A enzyme in brain cells. Such lipid-based nanostructures are attractive tools for both oral and nasal administration, supporting the development of novel materials for the food and medical industrial practices.
Paula B Andrade
Associate Professor with habilitation
Please note, this article will appear in issue 33 of Scitech Europa Quarterly, which is available in December 2019.