Traditional uses, phytochemicals, and biological properties of Saba senegalensis.

The fruit of Saba senegalensis is respectively known among local folks in Ghana, Senegal, and Burkina Faso as εsononantin, maad and weda. The plant has been used traditionally, ethnobotanically, and medicinally in most West African countries. The phytochemicals that have been discovered in various extracts of S. senegalensis parts include alkaloids, coumarins, anthracene glycosides, anthocyanosides, anthocyanins, coumarins, flavonoids, saponins, saponin glycosides, sterols, condensed tannins, tannins, triterpenes, and triterpenoids. Presently, isolation and characterisation of phytochemicals from various parts of S. senegalensis has not been fully explored since scientists have isolated only two steroidal alkaloids from the stem of the plant namely Irehine and Homoandrost-9-ene-17ß,17aß-diol-3ß-(methylamino)-17aα-methyl-12-one. The phytochemicals have shown biological properties such as anti-oxidant, anti-inflammatory, anthelmintic, anti-microbial, analgesic, larvicidal, ovicidal, myostimulant, hypotensive, anti-diabetic, anti-lipid peroxidation and anti-mycobacterial effects. Additionally, isolation and characterisation of medicinally beneficial phytochemicals from various parts of the plant, namely latex, leaf, stem, flower, root, fruit, and bark should be comprehensively investigated. Thus, this current review summarises the traditional uses, phytochemicals, and biological properties of various parts of the plant.

Chirality-influenced antibacterial activity of methylthiazole- and thiadiazole-based supramolecular biocompatible hydrogels.

Chiral stereochemistry is a unique and fundamental strategy that determines the interaction of bacteria cells with chiral biomolecules and stereochemical surfaces. The interaction between bacteria and material surface (molecular chirality or supramolecular chirality) plays a significant role in modulating antibacterial performance. Herein, we developed inherent chiral antibacterial hydrogels by modifying the carboxyl groups of our previously reported supramolecular gelator (LPF-left handed phenylalanine gelator and DPF- right handed phenylalanine gelator) with 2-amino-5-methylthiazole (MTZ) and 5-amino-1,3,4-thiadiazole-2- thiol (TDZ). The new L/D-gelator molecules initiate self-assembly to form hydrogels through non-covalent interactions (Hydrogen bonding and π-π interactions) verified by FTIR and CD spectroscopy. Morphological studies of the xerogels revealed left and right-handed chiral nanofibers for the gelators' L-form and D-form, respectively. The resulting hydrogels exhibited inherent antibacterial activity against Gram-positive (Bacillus subtilis, Staphylococcus aureus) and Gram-negative (Pseudomonas aeruginosa) bacteria, with TDZ hydrogels showing more significant antibacterial activity than MTZ hydrogels. Interestingly, the D-form (having right-handed nanofibers) of both hydrogels (MTZ and TDZ) exhibited higher antibacterial activities compared with the left-handed nanofibrous hydrogels (L-form) attributed to the stereoselective interaction of the chiral helical nanofiber. Moreover, the amplification of chirality moving from a molecular to a supramolecular level essentially improved the antibacterial action. Our results provide deep insight into the development of unique supramolecular chiral antimicrobial agents and hint at the potentiality of right-handed nanofibers (D-form) having enhanced antibacterial activity. STATEMENT OF SIGNIFICANCE: Chiral stereochemistry plays a significant role in many biological processes, which determines the interaction of bacteria cells with chiral biomolecules. The interaction between bacteria and material surface (molecular chirality or supramolecular chirality) plays a significant role in modulating antibacterial performance. Here, we deigned and synthesized unique inherent biocompatible supramolecular chiral hydrogel. From this study we concluded that the D-form (having right-handed nanofibers) of hydrogels exhibited higher antibacterial activities compared with the left-handed nanofibrous hydrogels (L-form) attributed to the stereoselective interaction of the chiral helical nanofiber. Additionally, this study also explored the amplification of chirality moving from a molecular to a supramolecular level essentially improved the antibacterial action.

Lectin-Glycan-Mediated Nanoparticle Docking as a Step toward Programmable Membrane Catalysis and Adhesion in Synthetic Protocells.

The spontaneous assembly of nanoscale building blocks into continuous semipermeable membranes is a key requirement for the structuration of synthetic protocells. Engineering the functionality and programmability of these building units provides a step toward more complex cell-like entities with adaptive membrane properties. Inspired by the central role of protein (lectin)-carbohydrate interactions in cellular recognition and adhesion, we fabricate semipermeable polysaccharide-polymer microcapsules (polysaccharidosomes) with intrinsic lectin-binding properties. We employ amphiphilic polysaccharide-polymer membrane building blocks endowed with intrinsic bio-orthogonal lectin-glycan recognition sites to facilitate the reversible noncovalent docking of functionalized polymer or zeolitic nanoparticles on the polysaccharidosomes. We show that the programmed attachment of enzyme-loaded nanoparticles gives rise to a membrane-gated spatially localized cascade reaction within the protocells due to the thermoresponsiveness of the polysaccharidosome membrane, and we demonstrate that extended closely packed networks are produced via reversible lectin-mediated adhesion between the protocells. Our results provide a step toward nanoscale engineering of bioinspired cell-like materials and could have longer-term applications in synthetic virology, protobiology, and microbiosensor and microbioreactor technologies.

Antimicrobial Activity with Enhanced Mechanical Properties in Phenylalanine-Based Chiral Coassembled Hydrogels: The Influence of Pyridine Hydrazide Derivatives.

Hydrazide derivatives are known to display a wide range of biological properties including antimicrobial activities, hence making them desirable candidates for soft biomaterials. Herein, we report chiral supramolecular coassembled hydrogels obtained from two phenylalanine gelators (L/DPF and B2L/D) and two dicarbohydrazide molecules (pyridine-2,6-dicarbohydrazide (PDH) and (2,2'-bipyridine)-5,5'-dicarbohydrazide (BDH)) that exhibited enhanced mechanical properties, chirality modulation, and antimicrobial activity. Four lines of coassembled hydrogels were obtained (i.e., L/DPF-PDH, L/DPF-BDH, B2L/D-PDH, and B2L/D-BDH) through hydrogen bonding and π-π stacking with some level of an interpenetrating network, as revealed by the structural characterization analysis. Mechanical properties were significantly improved, especially in the case of hybrid gels involving BDH, with improved average elastic modulus (G') values of 3430 and 3167 Pa for DPF-BDH and B2D-BDH (1:3, molar concentration) over 140 and 1680 Pa for DPF and B2D gelators, respectively. This was attributed to the improved π-π stacking and interpenetrating network due to the bipyridine group and its ease to form fibrous precipitates in the process of heating and cooling to room temperature. PDH, on the other hand, was able to modulate chirality in the L/DPF gelator due to its more planar and less bulky nature and showed antimicrobial activity against Pseudomonas aeruginosa (Gram-negative). Interestingly, when PDH was coassembled with the B2L/D gelator, the hybrid gels exhibited antimicrobial activity against Staphylococcus aureus (Gram-positive) and P. aeruginosa (Gram-negative) by virtue of a synergistic effect of the gelator and the azomethine group of PHD. Hence, by moving from bipyridine (BDH) to pyridine (PDH) as a core structure in the hydrazide molecules, the resulting hybrid hydrogels exhibited desirable properties of antimicrobial activity and improved mechanical attributes.

Achiral isomers controlled circularly polarized luminescence in supramolecular hydrogels.

Although chiral functional materials showing circularly polarized luminescence (CPL) are being widely reported, it remains a challenge to provide convenient and universal strategies for constructing controllable CPL-active materials with a high luminescence dissymmetry factor (glum). Herein, the supramolecular chirality as well as the CPL handedness of phenylalanine-based hydrogels can be effectively regulated by commercial achiral naphthylamine isomers through non-covalent interactions. Typically, the co-assembled hydrogels exhibit considerably high |glum| values in the range of 5.62 × 10-3-8.74 × 10-3. The CPL inversion is mainly facilitated by intermolecular hydrogen bonds and π-π stacking between the achiral and chiral molecules, which might be induced by the reorientations of the assembled molecules. This work may provide an alternative method to construct tunable CPL-active materials.

Mechanically Stable C2-Phenylalanine Hybrid Hydrogels for Manipulating Cell Adhesion.

Tuning of the viscoelastic properties of supramolecular hydrogels to be used as biological material substrates in tissue engineering has become significantly relevant in recent years due to their ability to influence cell fate. In the quest to enhance the stability and mechanical properties of a derived C2-phenylalanine gelator (LPF), derivatives of the polysaccharide dextran were incorporated as additives to promote hydrogen bonding and π-π stacking with the gelator. Dextran was esterified to yield carboxymethyl dextran (CMDH), which was subsequently amidated to furnish amino dextran (AD), the resulting hybrid hydrogels were denoted as LPF-ADx and LPF-CMDHx, where x represents the amount of AD and CMDH (mg). The LPF gelator interacted with the carboxyl and amino functional groups of the CMDH and AD, respectively, through hydrogen bonding and π-π stacking, resulting in mechanically stable hydrogels. Morphological studies revealed that the hybrid hydrogels were formed as a result of dense highly branched thin and broad fibers for LPF-AD and LPF-CMDH, respectively. Rheological studies confirmed the superiority of the hybrid hydrogels over the neat hydrogel, where LPF-CMDH3 exhibited the best mechanical properties with an improved elastic modulus of 11 654 Pa over 1518 and 140 Pa for LPF-AD4.5 and LPF, respectively. The adhesion and spreading behavior of NIH 3T3 fibroblast cells were significantly improved on the LPF-CMDH3 substrate owing to their enhanced mechanical properties. The tuning of the mechanical properties of the therein hydrogels via the facile incorporation of biodegradable and biocompatible functionalized additives opens up avenues for strengthening the supposed weak supramolecular gelators and hence increasing their potential of being employed largely in the field of tissue engineering.

Modulating Supramolecular Chirality in Alanine Derived Assemblies by Multiple External Stimuli.

Having control over the supramolecular chirality through multiexternal stimulators provides many possibilities in realizing functional chiral materials. Herein, the supramolecular chirality of nanotwists comprising PA centered with 1,4-phenyldicarboxamide bearing two l/d-helicogenic alanine motifs and achiral COOH at each terminus of the alanine arms is modulated by solvent, temperature, and ultrasound. The modulations are mainly due to the hydrogen bonds among gelators and solvent-gelator interactions, resulting in changes of the molecular arrangement and subsequent self-assembled nanostructures. Typically, the gel of PA in ethyl acetate prepared by ultrasonication method exhibits thixotropic property due to the participation of ethyl acetate in the self-assembly process, resulting in relatively flexible and tolerant networks. This study provides a simplistic way to control the handedness of chiral nanostructures and a rational design of the self-assembly system with multistimuli-responsive supramolecular chirality.

The Cooperative Effect of Both Molecular and Supramolecular Chirality on Cell Adhesion.

Although helical nanofibrous structures have great influence on cell adhesion, the role played by chiral molecules in these structures on cells behavior has usually been ignored. The chirality of helical nanofibers is inverted by the odd-even effect of methylene units from homochiral l-phenylalanine derivative during assembly. An increase in cell adhesion on left-handed nanofibers and weak influence of cell behaviors on right-handed nanofibers are observed, even though both were derived from l-phenylalanine derivatives. Weak and negative influences on cell behavior was also observed for left- and right-handed nanofibers derived from d-phenylalanine, respectively. The effect on cell adhesion of single chiral molecules and helical nanofibers may be mutually offset.

Analyse démographique et endoscopique des patients atteints d'ulcère gastroduodénal à Yaoundé au Cameroun : qu'est ce qui a changé depuis les années 1990 ?

Objectif : La prévalence de l'ulcère gastro-duodénal semble être en diminution marquée ces dernières années dans les pays africains. Au Cameroun en 1990, elle était de 32%. L'objectif de notre étude était d'évaluer l'évolution de la prévalence de l'ulcère gastroduodénal et d'identifier ses caractéristiques démographiques et endoscopiques à Yaoundé, 25 ans après.Patients et méthodes : Etude rétrospective de la période allant du 1er janvier 2011 au 31 décembre 2014 dans trois hôpitaux universitaires de Yaoundé. Les comptes rendus d'endoscopie de 4685 patients consécutifs référés pour une endoscopie digestive haute ont été réexaminés. Nous avons inclus 489 patients (312 hommes et 177 femmes) avec un ulcère gastro-duodénal prouvé en endoscopie. Les données démographiques et endoscopiques ont été recueillies. Résultats : L'ulcère duodénal et l'ulcère gastrique étaient identifiés respectivement chez 295 (60,3%) et 157 (32,1%) patients, la double localisation gastrique et duodénale chez 37(7,6%), faisant une prévalence globale de 10,4%. L'âge moyen des patients était de 48,9 ans (extrêmes : 4 à 90 ans). Les patients ulcéreux gastriques étaient relativement plus âgés que les patients ulcéreux duodénaux (54,4 ans vs. 45,4 ans, p < 10-5). Le ratio homme/femme était de 2,2/1 pour l'ulcère duodénal et 1,2/1 pour l'ulcère gastrique. La prévalence globale de l'infection à H. pylori à l'histologie et/ou au test rapide à l'uréase était de 63,0% (308/489). L'infection était plus fréquente dans l'ulcère duodénal que gastrique (67,8% vs. 51,0%, p = 0,0005). L'ulcère gastro-duodénal était révélé par les épigastralgies (71,8%) et l'hémorragie (31,5%). L'hémorragie était liée à l'ulcère duodénal (p = 0,07) et au sexe masculin (p = 0,01). Il n'y avait pas de différence significative selon l'âge (p = 0,16). H. pylori protégeait contre l'hémorragie, risque relatif 0,7 (IC à 95% : 0,6-0,8 ; p = 0,00006).Conclusion : La prévalence de l'ulcère gastroduodénal a significativement diminué au Cameroun par rapport à 1990. Les patients ulcéreux sont devenus plus âgés avec une tendance à l'occidentalisation de la maladie ulcéreuse

MiRNA let-7g regulates skeletal myoblast motility via Pinch-2.

Post-transcriptional regulation of gene expression by RNA-binding proteins and by small non-coding RNAs plays an important role in cell biology. Our previous results show that in murine skeletal myoblasts, the expression of Pinch-2, a focal adhesion remodeling factor that regulates cell motility, is repressed by an RNA-binding protein IMP-2/Igf2bp2. We now show that the expression of Pinch-2 is also regulated by the miRNA let-7g. Let-7g and IMP-2 repress Pinch-2 expression independently of each other. A knock-down of let-7g leads to an increase in Pinch-2 expression, and to a decrease of cell motility, which can be reversed by a simultaneous knock-down of Pinch-2. We conclude that let-7g controls the motility of mouse myoblasts in cell culture by post-transcriptionally regulating the expression of Pinch-2.