Context
Madagascar and the satellite volcanic archipelagos: the Seychelles, the Comoros, Mauritius (including Rodrigues), the Scattered Islands as well as the French Overseas Departments Reunion and Mayotte, constitute one of the hotspots of terrestrial and marine biodiversity worldwide . These tropical islands form a unique jewel, containing a biological treasure of the most precious and without equivalent on a planetary scale. The level of endemism is particularly high. However, due to the extreme vulnerability of these island ecosystems to human impacts (alteration and loss of habitat, introduction of invasive species, destructive harvesting methods and overexploitation of natural resources), flora and fauna of this Hotspot are greatly threatened. The effects of extreme natural phenomena such as cyclones or volcanic flows can also be periodically important. Moreover, the responses to environmental threats in most of the islands of this Hotspot encounter several constraints:
1- Infrastructure and technical expertise are weak;
2- The general public is not very sensitive to environmental problems because it does not understand the issues;
3- Aspects related to the environment are poorly integrated and not taken into account in the development policies put in place;
4- Information on the state of natural resources and biodiversity is insufficient.
On this last point, the contribution of scientists is paramount. Researchers can, in fact, act for a better census of biodiversity and a better understanding of the evolutionary processes of this biodiversity. This information will be made available to politico-strategic decision-makers to better integrate them into regional concerns.
Among the research organizations active in favor of biodiversity in the South-Western part of the Indian Ocean, the University of Reunion has prioritized in its research strategy "the valorization and protection of terrestrial and marine biodiversity" . Its strategic position in the heart of the West Indian Ocean is an undeniable asset; it offers exceptional research conditions for the observation and study of biodiversity. Implanted at the University of La Réunion, the Laboratory of Chemistry of Natural Substances and Food Sciences (LCSNSA), through its studies on the chemodiversity carried out on both plants and marine organisms, actively contributes to the development of this theme of privileged research.
With particular reference to marine chemistry, the LCSNSA has made its mark in the field since the early 1990s. The laboratory's researchers are involved in the extraction, isolation and identification of secondary metabolites of marine invertebrates (sponges). mainly ascidians and alcyons).
Purpose of the research
The scientific mission carried out aboard the Antsiva is part of a research project carried by the LCSNSA (Jacqueline Smadja - Anne Bialecki) and financed by Europe and the Reunion Region (ERDF: European Development Fund Regional). This project, whose acronym is BIOMOL TCN, is entitled "Therapeutic, Cosmetological and Nutracetic Activities of Molecules derived from Terrestrial, Marine and Microbial Biodiversity in the Southwest Indian Ocean" and started during the year 2012.
On board the Antsiva, we set ourselves the mission of collecting marine invertebrates (Sponges, Ascidians and Soft Corals) located near the Mitsio Islands in northern Madagascar. All these invertebrates are intended for an exhaustive study of their chemical composition with a double objective:
Objective 1: Finding new drug candidates
This research will make it possible to discover original molecules with interesting structural and / or pharmacological properties. Natural substances have in fact always been considered as the preferred source for the discovery of drugs or active substances. It is estimated that more than 60% of drugs are either natural substances, derivatives or analogues, or molecules synthesized on the model of natural substances.
Pendant de nombreuses années, la recherche s’est concentrée sur les plantes et les micro-organismes terrestres, principalement parce que ces spécimens sont facilement accessibles. Aujourd’hui, une part croissante des promesses actuelles de la recherche pharmaceutique réside dans la mer dont les profondeurs sont peuplées d’une biodiversité d’une richesse remarquable. A cette biodiversité est associée une chimiodiversité fascinante laissant entrevoir une extraordinaire multiplicité de nouvelles possibilités en matière de découvertes pharmaceutiques. Il est aujourd’hui reconnu que les produits naturels marins sont les représentants les plus originaux de la diversité moléculaire. Les organismes marins, vivant dans un milieu hautement compétitif, produisent en effet des métabolites secondaires uniques qui ont des rôles écologiques essentiels à l’équilibre des biotopes (compétition pour l’espace, colonisation des surfaces, défense contre la prédation, séduction pour la reproduction…). La spécificité et l’originalité des molécules issues des organismes marins s’expliquent également par l’ensemble des caractéristiques physico-chimiques particulières du milieu marin telles que les fortes pressions, l’absence totale de lumière, des salinités variables ou la relative abondance d’éléments comme le brome, le chlore ou l’iode. Les invertébrés marins tels que les Eponges, les Ascidies et les Coraux mous font partie des organismes les plus étudiées pour leur composition chimique. Parmi les composés isolés de ces organismes sessiles, des molécules à activités biologiques (anticancéreux, antiviral, anti-inflammatoire, antibiotique, immunosuppresseur, anti-Alzheimer…) ont été découvertes, et sont en phase d’essais précliniques ou cliniques.
Goal 2: Understand and safeguard marine biodiversity
The proposed research will contribute to the characterization of the marine biodiversity of the Southwest Indian Ocean zone through its chemical component. Chemical communication is indeed a universal mode of communication to all living beings - from unicellular plants or animals to the most complex beings. At sea even more than on land, the use of chemical mediators by living organisms is an indispensable element in establishing intra- and interspecific relations. This is especially true since among marine organisms several thousand species - this is the case for most marine invertebrates - are sessile and lack sensory organs such as vision and hearing.
Chemical ecology, with the study of the role of secondary metabolites in the mediation of biotic interactions, is at the heart of fundamental questions in evolutionary biology and functional ecology, on the functioning of ecosystems and on the dynamics and maintenance of biodiversity.
Methodology
The planned works include 4 basic steps:
1. The collection of marine invertebrates
Cette étape a été réalisée à bord de l’Antsiva au large des îles Mitsio. Les observations et prélèvements des organismes ont été réalisés en plongée autonome à l’air comprimé jusqu’à 25 m de profondeurs. Les plongeurs ont opéré en trinôme.
Les prélèvements d’invertébrés marins (Eponges, Ascidies et Alcyons) ont été effectués à la main ou à l’aide d’un couteau en fonction de la taille des organismes et de leur mode d’accrochage au substrat. Pour l’ensemble des études (taxonomie, phylogénétique, chimie, bioactivité) le but a été de récolter environ 500 g (poids mouillé) pour les éponges et coraux mous, entre 200 et 400 g pour les ascidies. Chaque organisme collecté a été photographié dans son environnement naturel.
Au retour de la plongée, pour chaque station, les récoltes ont été triées, puis, chaque taxon référencé par un code faisant apparaître la zone géographique (MAD : Madagascar), l’année de récolte 12 (2012) et un chiffre croissant (e.g. MAD13-001). Une photographie numérique a ensuite été réalisée ainsi qu’une description précise rappelant: la forme, la couleur, la consistance ainsi que toutes les caractéristiques pouvant aider ultérieurement à la détermination taxonomique.
The samples were then stored aboard the Antsiva in the freezer (at -20 ° C) and transported frozen to the Laboratory of Chemistry of Natural Substances and Food Sciences at the University of Reunion. These samples are kept frozen until chemistry studies and taxonomy and molecular phylogeny studies begin for accurate identification.
2. The selection of marine invertebrates to study
A selection of marine invertebrates to be studied is carried out in the laboratory. Each organism is subjected to standardized protocols of extraction, biological tests on defined targets (cytotoxic activities, antimalarial, anti-chikungunya ...), and first global chemical analysis (otherwise called metabolomics) by high performance liquid chromatography coupled with a mass spectrometer and nuclear magnetic resonance. The results of biological tests and chemical signatures obtained after these first treatments then allow a reasoned selection of organisms to be chemically studied. The selected marine invertebrates are then subjected to a comprehensive analysis of their chemical composition.
3. The chemical study of selected invertebrates
The secondary metabolites contained in the selected marine invertebrates are first isolated and purified by different chromatographic techniques and then identified using spectroscopic techniques such as high-resolution mass spectrometry and mono and two-dimensional nuclear magnetic resonance.
Purified and isolated, these molecules are then tested on various pharmacological targets to evaluate their biological activities: anticancer activities or antiviral (Dengue malaria, Chikungunya ...).
4. The valuation of the results
The valuation of the results will be carried out in the form of possible patent filings, scientific publications and participation in scientific congresses.
