Roméo Arago Dougué Kentsop

Green seaweeds are important and highly diffused marine biomass representing at the same time an environmental concern and a precious resource. Among these, Ulva spp. are globally widespread and characterized by the presence of ulvan as a primary constituent. Ulvan are peculiar polyanionic heteropolysaccharide revealing important features for their use in medical and high-added value applications. The ulvan extraction process generates a series of residues so far largely unexplored. In the present work, the spent solid output (SSO), still rich in organic components, has been studied and valorized by designing an innovative biomaterial. A series of transparent thermoplastic films was successfully prepared from SSO plasticized by glycerol through extrusion and moulding techniques. The biomaterial formulated with 30 wt.% of glycerol, which exhibited an elastic modulus of 300 MPa and a tensile strength of 6 MPa, was evaluated for potential agronomic applications. Preliminary experiments carried out in maize growth revealed in the treated plants a greater branching and a higher density of root hairs as well as a faster five-leaf stage achievement.

The use of natural bioactive compounds in edible coatings provides a sustainable approach to reducing food spoilage and meeting consumer demand for safer food preservation. In this study, bioactive extracts from Brassica juncea (green mustard, GM) and Raphanus sativus (radish tango, RT) sprouts were encapsulated into zein/chitosan (Z/CH) microparticles (MPs) using a complex coacervation–based encapsulation approach. The encapsulated microparticles (MPs), characterized by FTIR and UV-Vis spectroscopy, demonstrated a high loading efficiency of up to 90% and maintained their antioxidant activity for up to 168 h. TGA and SEM tests confirmed that the edible films produced by incorporating these microparticles (MPs) into polyvinyl alcohol (PVA) and chitosan (CH) matrices had a more uniform microstructure and enhanced heat stability. The Z/CH/RT6:PVA (1:2) and Z/CH/GM6:CH (1:1) formulations of the films showed significant antioxidant and antibacterial action, with up to 22.4% DPPH inhibition and a 1-log decrease in Salmonella enterica CFU, respectively. Overall, the results underscore the promise of sprout-derived microparticles as components for developing active, biodegradable packaging films with improved functional properties.

The screening of plant-derived compounds with anti-cancer properties is a promising strategy to meet the growing need for new, safe and effective anti-cancer drugs. Justicidin B is a plants secondary metabolite that displays anti-cancer properties in several tumor cells. Therefore, it represents a good candidate. We used the 3R-compliant organism Caenorhabditis elegans to evaluate the safety of justicidin B produced by in vitro-grown adventitious roots of Linum lewisii. We showed that a dose of 100 µg/mL justicidin B does not affect worm vitality in either short-term or chronic administration; in contrast, the 200 µg/mL dose induces a lifespan reduction, but only in short-term daily treatment. We attributed this effect to its accumulation in lipofuscin granules in the pharynx as observed through confocal analysis. HPLC analysis confirmed the higher accumulation justicidin B with a 200 µg/mL dose but also revealed the presence of metabolic derivatives that could be responsible for the toxicity. We also demonstrated that the 100 µg/mL dose does not affect worm fertility or development. Our results highlight the safety of justicidin B, supporting its employment in cancer therapy, and encourage the use of a C. elegans model as an appropriate tool to assess compounds’ toxicity before moving to more complex organisms.

Plant secondary metabolites have great applications in the nutritional and cosmetic aspects of human health. Terpenes, and in particular bioactive diterpenoids, represent an important group of compounds found in Salvia species. Their production in plants is often limited, and chemical synthesis is often not economically feasible. Biotechnological approaches using plant cell and tissue cultures can be routinely established under sterile conditions from explants for biomass production and the extraction of secondary metabolites. The biosynthesis and accumulation of bioactive diterpenoids in vitro in Salvia cells and tissues can be enhanced by strain improvement, techniques to select high-producing cell lines, optimisation of the growth medium, use of specific precursors or elicitors, induction of their release into the culture medium, and the overexpression of genes. This review analyses the biotechnological techniques applied to the in vitro culture of Salvia cells and tissues to enhance the production and accumulation of bioactive diterpenoids and summarises their biological activities.

Plants synthesize specific secondary metabolites for survival, reproduction, environmental resilience, and defense. Among them, lignans are a class of polyphenols with several bioactive properties: chemopreventive, anti-inflammatory, antiviral, and antioxidant. These compounds are often extracted from field-grown plants with very low yields. To overcome these constraints, in vitro tissue cultures provide a tool to optimize large-scale production. Moreover, the use of elicitation to increase secondary metabolite production is gaining importance. The aim of this work was to develop adventitious (ARL) and hairy roots (HRL) from Linum lewisi, a species able to synthesize arylnaphthalene lignans such as justicidin B. The ARL and HRL were obtained for the first time and characterized for their phenol content, antioxidant activity, and the production of justicidin B after treatments with several elicitors and precursor feeding. Through NMR spectroscopy, other four lignans were highlighted and identified in the roots extracts. A pilot-scale bioreactor was adopted to assess the suitability of the developed root cultures for future large-scale production. The ARL and HRL cultures showed a justicidin B production higher than other Linum species cultures described up to now (75.8 mg/L and 82.2 g/L), and the production more than doubled after elicitation with MeJA.

Lignans are plant phenols derived from phenylpropanoids. They play a significant role in plant defense and have features that make them appealing for pharmaceutical applications. Lignans can be obtained by plant in vitro cultures; their production by adventitious and hairy roots of Linum species seems to be a promising alternative to chemical synthesis. In the context of large-scale production, it is necessary to optimize their extraction from plants tissue by choosing the more suitable solvent and extraction procedure, paying attention to the use of green media and methods. With the aim to select the best conditions for the extraction of two interesting lignans (justicidin B and 6-methoxypodophyllotoxin) from Linum tissues, different green solvents and the method of ultrasound-assisted extraction were tested. The results showed that ethyl methyl ketone and dimethyl carbonate were the best media to extract justicidin B and 6-methoxypodophyllotoxin, respectively, in terms of purity and recovery. Moreover, we showed that ultrasound-assisted extraction presents different advantages compared to conventional methods. Finally, the optimal experimental conditions to extract justicidin B from L. austriacum hairy roots using methyl ethyl ketone were also determined by the response surface method. The models obtained are reliable and accurate to estimate the purity and recovery of justicidin B.

Quorum-sensing (QS) is a regulatory mechanism in bacterial communication, important for pathogenesis control. The search for small molecules active as quorum-sensing inhibitors (QSI) that can synergize with antibiotics is considered a good strategy to counteract the problem of antibiotic resistance. Here the antimicrobial labdane diterpenoids sclareol (1) and manool (2) extracted from Salvia tingitana were considered as potential QSI against methicillin-resistant Staphylococcus aureus. Only sclareol showed synergistic activity with clindamycin. The quantification of these compounds by LC–MS analysis in the organs and in the calli of S. tingitana showed that sclareol is most abundant in the flower spikes and is produced by calli, while manool is the major labdane of the roots, and is abundant also in the leaves. Other metabolites of the roots were abietane diterpenoids, common in Salvia species, and pentacyclic triterpenoids, bearing a γ-lactone moiety, previously undescribed in Salvia. Docking simulations suggested that 1 and 2 bind to key residues, involved in direct interactions with DNA. They may prevent accessory gene regulator A (AgrA) binding to DNA or AgrA activation upon phosphorylation, to suppress virulence factor expression. The antimicrobial activity of these two compounds probably achieves preventing upregulation of the accessory gene regulator (agr)-regulated genes.

Lignans are the main secondary metabolites synthetized by Linum species as plant defense molecules. They are also valuable for human health, in particular, for their potent antiviral and antineoplastic properties. In this study, the adventitious root cultures of three Linum species (L. flavum, L. mucronatum and L. dolomiticum) were developed to produce aryltetralin lignans. The effect of two elicitors, methyl jasmonate and coronatine, on aryltetralin lignans production was also evaluated. The adventitious root cultures from L. dolomiticum were obtained and analyzed for the first time and resulted as the best producer for all the aryltetralins highlighted in this system: Podophyllotoxin, 6-methoxypodophyllotoxin and 6-methoxypodophyllotoxin-7-O-β-glucoside, the last showing a productivity of 92.6 mg/g DW. The two elicitors differently affected the production of the 6-methoxypodophyllotoxin and 6-methoxypodophyllotoxin-7-O-β-glucoside.

Salvia corrugata Vahl. is an interesting source of abietane and abeo-abietane compounds that showed antibacterial, antitumor, and cytotoxic activities. The aim of the study was to obtain transformed roots of S. corrugata and to evaluate the production of terpenoids in comparison with in vivo root production. Hairy roots were initiated from leaf explants by infection with ATCC 15834 Agrobacterium rhizogenes onto hormone-free Murashige and Skoog (MS) solid medium. Transformation was confirmed by polymerase chain reaction analysis of rolC and virC1 genes. The biomass production was obtained in hormone-free liquid MS medium using Temporary Immersion System bioreactor RITA^®. The chromatographic separation of the methanolic extract of the untransformed roots afforded horminone, ferruginol, 7-O-acetylhorminone and 7-O-methylhorminone. Agastol and ferruginol were isolated and quantified from the hairy roots. The amount of these metabolites indicated that the hairy roots of S. corrugata can be considered a source of these compounds.

Lignans are the main secondary metabolites synthetized by Linum species as plant defense compounds but they are also valuable for human health, in particular, for novel therapeutics. In this work, Linum austriacum in vitro cultures, cells (Cc), adventitious roots (ARc) and hairy roots (HRc) were developed for the production of justicidin B through elicitation with methyl jasmonate (MeJA) and coronatine (COR). The performances of the cultures were evaluated for their stability, total phenols content and antioxidant ability. NMR was used to identify justicidin B and isojusticidin B and HPLC to quantify the production, highlighting ARc and HRc as the highest productive tissues. MeJA and COR treatments induced the synthesis of justicidin B more than three times and the synthesis of other compounds. RNA-sequencing and a de novo assembly of L. austriacum ARc transcriptome was generated to identify the genes activated by MeJA. Furthermore, for the first time, the intracellular localization of justicidin B in ARc was investigated through microscopic analysis. Then, HRc was chosen for small-scale production in a bioreactor. Altogether, our results improve knowledge on justicidin B pathway and cellular localization in L. austriacum for future scale-up processes.