In the current paper, we fabricated, characterized, and applied nanocomposite hydrogel based on alginate (Alg) and nano-hydroxyapatite (nHA) loaded with phenolic purified extracts from the aerial part of Linum usitatissimum (LOH) as the bone tissue engineering scaffold. nHA was synthesized based on the wet chemical technique/precipitation reaction and incorporated into Alg hydrogel as the filler via physical cross-linking. The characterizations (SEM, DLS, and Zeta potential) revealed that the synthesized nHA possess a plate-like shape with nanometric dimensions. The fabricated nanocomposite has a porous architecture with interconnected pores. The average pore size was in the range of 100–200 µm and the porosity range of 80–90%. The LOH release measurement showed that about 90% of the loaded drug was released within 12 h followed by a sustained release over 48 h. The in vitro assessments showed that the nanocomposite possesses significant antioxidant activity promoting bone regeneration. The hemolysis induction measurement showed that the nanocomposites were hemocompatible with negligible hemolysis induction. The cell viability/proliferation confirmed the biocompatibility of the nanocomposites, which induced proliferative effects in a dose-dependent manner. This study revealed the fabricated nanocomposites are bioactive and osteoactive applicable for bone tissue engineering applications.

Flax (Linum usitatissimum) is a plant grown in temperate regions either for its fiber or for its seeds, which are rich in the essential fatty acid omega-3. It is also well known as a source of medicinal compounds. The chemical composition of its leaves is currently poorly described. In order to fill this gap, we have conducted a comprehensive analysis of flax leaf metabolome. The exploration of the metabolome allowed the characterization of compounds isolated for the first time in flax leaves. These molecules were isolated by preparative HPLC and then characterized by NMR, LC-MS and standard analysis. This work extended our picture of C-glycosyl-flavonoids and coniferyl alcohol derivatives accumulated in flax. The follow-up of the content of these different metabolites via UPLC-MS revealed significant accumulation differences in spring and winter flax leaves. In particular, two methylated C-glycosylflavonoids (swertisin and swertiajaponin) were the most abundant phenolic compounds in winter flax whereas they were not detected in spring flax. This result suggests that these 2 compounds are involved in cold stress tolerance in flax.

Flavonoids have been documented to have good antioxidant activities in vitro. In recent years, reports on the antioxidant activities of flavone C-glycosides, a subclass of flavonoids, have attracted great attention. Despite the wealth of information on this subject, the correlation between structure and function is not well understood. In this work, the relationship between the structure and the antioxidant activity of 12 flavone C-glycosides extracted from the aerial part of winter linseed (Linum usitatissimum L.) was studied to fill the current gaps. Orientin, isoorientin, vitexin, isovitexin, swertisin, swertiajaponin, carlinoside, schaftoside, lucenin-1, lucenin-2, vicenin-1, and vicenin-2 were purified by preparative HPLC and by the drowning-out crystallization method. Then, the control of the purity and the confirmation of the chemical structures were assessed by LC-MS and NMR analyses. The antioxidant activity was evaluated using ABTS, CUPRAC, FRAP, and iron chelating activity in vitro assays. Luteolin and its flavone C-glycoside derivatives exhibited higher antioxidant activity than apigenin and its flavone C-glycosides derivatives. This could be attributed to the ortho-dihydroxyl groups at C-3′ and C-4′ of the B ring in the flavonoid skeleton, which seemed to play an important role in antioxidant behavior. These results indicate that the antioxidant activity of these compounds, derived from apigenin and luteolin, can be closely related to their structural characteristics, including the position and nature of the sugars, the number of hydroxyl groups, and the presence of methyl group.

Flax for oil seed is a crop of increasing popularity, but its cultivation needs technical improvement. Important agronomic traits such as productivity and resistance to stresses are to be regarded as the result of the combined responses of individual organs and their inter-communication. Ultimately, these responses directly reflect the metabolic profile at the cellular level. Above ground, the complexity of the plant phenotype is governed by leaves at different developmental stages, and their ability to synthesise and exchange metabolites. In this study, the metabolic profile of differently-developed leaves was used firstly to discriminate flax leaf developmental stages, and secondly to analyse the allocation of the metabolites within and between leaves. For this purpose, the concentration of 52 metabolites, both primary and specialized, was followed by gas chromatography (GC-) and liquid chromatography coupled to mass spectrometry (LC-MS) in alternate pairs of flax leaves. On the basis of their metabolic content, three populations of leaves in different growth stages could be distinguished. Primary and specialized metabolites showed characteristic distribution patterns, and compounds similarly evolving with leaf age could be grouped by the aid of the Kohonen self-organising map (SOM) algorithm. Ultimately, visualisation of the correlations between metabolites via hierarchical cluster analysis (HCA) allowed the assessment of the metabolic fluxes characterising different leaf developmental stages, and the investigation of the relationships between primary and specialized metabolites.