Natural Products from Herbal Medicine Self-Assemble into Advanced Bioactive Materials

Novel biomaterials are becoming more crucial in treating human diseases. However, many materials require complex artificial modifications and synthesis, leading to potential difficulties in preparation, side effects, and clinical translation. Recently, significant progress has been achieved in terms of direct self-assembly of natural products from herbal medicine (NPHM), an important source for novel medications, resulting in a wide range of bioactive supramolecular materials including gels, and nanoparticles. The NPHM-based supramolecular bioactive materials are produced from renewable resources, are simple to prepare, and have demonstrated multi-functionality including slow-release, smart-responsive release, and especially possess powerful biological effects to treat various diseases. In this review, NPHM-based supramolecular bioactive materials have been revealed as an emerging, revolutionary, and promising strategy. The development, advantages, and limitations of NPHM, as well as the advantageous position of NPHM-based materials, are first reviewed. Subsequently, a systematic and comprehensive analysis of the self-assembly strategies specific to seven major classes of NPHM is highlighted. Insights into the influence of NPHM structural features on the formation of supramolecular materials are also provided. Finally, the drivers and preparations are summarized, emphasizing the biomedical applications, future scientific challenges, and opportunities, with the hope of igniting inspiration for future research and applications.

Recent Advances of Natural Pentacyclic Triterpenoids as Bioactive Delivery System for Synergetic Biological Applications

Bioactive compounds have drawn much attention according to their various health benefits. However, poor dissolvability, low stability and limited bioavailability largely narrow their applications. Although a variety of nontoxic ingredients have been rapidly developed as vehicles to deliver bioactive compounds in the last few years, most of them are non-bioactive. Pentacyclic triterpenoids, owing to their unique self-assembly and co-assembly behaviors and different physiological functions, can construct bioactive carriers due to their higher biodegradability, biocompatibility and lower toxicity. In this paper, the basic classification, biological activities and physicochemical properties of pentacyclic triterpenoids were summarized. Additionally, applications of self-assembled and co-assembled pentacyclic triterpenoids as bioactive delivery systems to load bioactive components and future research directions were discussed. This study emphasizes the potential of pentacyclic triterpenoids as bioactive delivery systems, offering a new perspective for constructing self- or co-assemblies for further synergetic biological applications.

Nanoparticle encapsulation using self-assembly abietic acid to improve oral bioavailability of curcumin

This research constructed composite nanoparticles (NPs) using abietic acid (AA) as a carrier for significantly enhancing the bioavailability of curcumin (CCM). CCM-loaded AA NPs were synthesized using a low-energy microemulsification method, and the obtained nanoparticles had a spherical morphology with an average diameter of 458.66 nm, a narrow size distribution and a negative surface charge of -19.13 mV. The encapsulation efficiency of CCM was 17.98 %, while its solubility was 20-fold that of free curcumin. FITR, UV, and MD revealed hydrogen bonds and hydrophobic forces between AA and CCM. Thein-vitrorelease profile showed sustainable release of CCM in simulated gastric and intestinal fluids up to 2 h at 37 °C. In cellular studies, CCM-loaded AA NPs with the same CCM concentration exhibited greater bioaccessibility and bioavailability than free CCM. These data suggested a possible utilization of AA NPs in improving water solubility, bioavailability and activity of lipophilic bioactive food factors.

Construction of a novel ursolic acid-based supramolecular gel for efficient removal of iodine from solution

Pentacyclic triterpenes is a natural amphipathic product which possess a rigid backbone and several polar functional groups such as hydroxyl, carbonyl and carboxyl groups. The amphipathic character makes it easy to realize self-assemble into complex nano structure and therefore attract extensive attention due to the simple synthetic processes and renewable raw materials. Hence, a novel Ursolic acid-based hydrogel was prepared successfully via a simple self-assembly of triterpenoid derivative in methanol by capture water molecule in air. The resulting hydrogel show a porous morphology and good elasticity including strong heat resistance. Based on the characteristic above, the hydrogel showed a good iodine adsorption capacity and can removal 75.0% of the iodine from cyclohexane solution and 66.3% from aqueous solution within 36 h. Data analysis indicate that all the iodine adsorption process are dominated by chemisorption and belongs to the multi-site adsorption on heterogenous surfaces. In addition, the obtained hydrogel also possesses a good recyclability which can maintain more than 82% of its capacity after 5 cycles. The simple preparation method and easily available raw materials endow it a great potential in future pollutant treatment.

Self-assembled renewable nano-sized pentacyclic triterpenoid maslinic acids in aqueous medium for anti-leukemic, antibacterial and biocompatibility studies: An insight into targeted proteins-compound interactions based mechanistic pathway prediction through molecular docking

Maslinic acid is a naturally occurring dihydroxy, mono-carboxy bioactive triterpenoid. Its bulky structure was the main hindrance in the path of biological activity. Sodium and potassium salts of nano-sized triterpenoid maslinic acid were prepared from maslinic acid and its self-assembly property was studied in aqueous and aqueous-organic binary liquid mixtures. Morphology of the compounds studied by Field Emission Scanning Electron Microscopy (FESEM), Atomic Force Microscopy (AFM), High Resolution Transmission Electron Microscopy (HRTEM), Optical Microscopy, Fourier Transform Infrared Spectroscopy (FTIR) and X-ray diffraction (XRD) revealed vesicular morphology of the self-assemblies. Selective cytotoxicity was performed in leukemic (K-562 and KG-1a) and PBMC cells. Among the three self-assemblies (maslinic acid 1, sodium maslinate 2 and potassium maslinate 3), sodium maslinate 2 showed better antileukemic efficacy. Sodium maslinate 2 induced apoptosis in leukemic cells by elevating ROS levels and disrupting the cellular antioxidant system. From the in-silico studies, it was confirmed that 2 interacted with extrinsic and intrinsic apoptotic proteins of leukemic cells and killed those cells by inducing apoptotic pathways. The compounds 1, 2 and 3 showed significant antibacterial efficacy against E.coli strain through binding with several periplasmic membrane fusion protein (MFP) and limiting the efflux system leading to arrestation of antimicrobial resistance.

Formation of a traditional Chinese medicine self-assembly nanostrategy and its application in cancer: a promising treatment

Traditional Chinese medicine (TCM) has been used for centuries to prevent and treat a variety of illnesses, and its popularity is increasing worldwide. However, the clinical applications of natural active components in TCM are hindered by the poor solubility and low bioavailability of these compounds. To address these issues, Chinese medicine self-assembly nanostrategy (CSAN) is being developed. Many active components of TCM possess self-assembly properties, allowing them to form nanoparticles (NPs) through various noncovalent forces. Self-assembled NPs (SANs) are also present in TCM decoctions, and they are closely linked to the therapeutic effects of these remedies. SAN is gaining popularity in the nano research field due to its simplicity, eco-friendliness, and enhanced biodegradability and biocompatibility compared to traditional nano preparation methods. The self-assembly of active ingredients from TCM that exhibit antitumour effects or are combined with other antitumour drugs has generated considerable interest in the field of cancer therapeutics. This paper provides a review of the principles and forms of CSAN, as well as an overview of recent reports on TCM that can be used for self-assembly. Additionally, the application of CSAN in various cancer diseases is summarized, and finally, a concluding summary and thoughts are proposed. We strongly believe that CSAN has the potential to offer fresh strategies and perspectives for the modernization of TCM.

Ursolic acid nanoparticles for glioblastoma therapy

BACKGROUND

Glioblastoma multiforme (GBM) is the most common and fatal primary tumor in the central nervous system (CNS). The effect of chemotherapy of GBM is limited due to the existence of blood-brain barrier (BBB). The aim of this study is to develop self-assembled nanoparticles (NPs) of ursolic acid (UA) for GBM treatment.

METHODS

UA NPs were synthesized by solvent volatilization method. Western blot analysis fluorescent staining and flow cytometry were launched to explore the anti-glioblastoma mechanism of UA NPs. The antitumor effects of UA NPs were further confirmed in vivo using intracranial xenograft models.

RESULTS

UA were successfully prepared. In vitro, UA NPs could significantly increase the protein levels of cleaved-caspase 3 and LC3-II to strongly eliminate glioblastoma cells through autophagy and apoptosis. In the intracranial xenograft models, UA NPs could further effectively enter the BBB, and greatly improve the survival time of the mice.

CONCLUSIONS

We successfully synthesized UA NPs which could effectively enter the BBB and show strong anti-tumor effect which may have great potential in the treatment of human glioblastoma.

Recent advances in natural small molecules as drug delivery systems

Drug delivery systems (DDSs) are a multidisciplinary approach toward the effective delivery of drugs to their target sites. Natural small molecule (NSM) compounds with anticancer activity, self-assembly and co-assembly functions show great potential for application as novel DDSs in the biomedical field. NSMs are widely sourced, have many modification sites, and readily form hydrogen bonds, π-π interactions, van der Waals interactions, and other non-covalent bonds in solvents, resulting in ordered structures. Moreover, their good biocompatibility and bioactivity allow compositions based on these compounds to be used in life science applications such as tissue engineering, drug delivery and cell imaging, showing the potential medical value of NSMs as DDSs. In this review, we summarise the role, assembly principles and applications of natural products such as triterpenoids, diterpenoids, sterols, alkaloids and polysaccharides in the construction of small molecule systems, which are expected to provide an important reference for the development of more active natural nanomaterials and the study of single or multi-component interactions.

Edible pentacyclic triterpenes: A review of their sources, bioactivities, bioavailability, self-assembly behavior, and emerging applications as functional delivery vehicles

Edible pentacyclic triterpenes (PTs) are a group of nutraceutical ingredients commonly distributed in human diets. Existing evidence has proven that they have various biological functions, including anticancer, antioxidant, anti-inflammatory and hypoglycemic activities, making them as "functional factor" for a long time. However, their properties of strong hydrophobicity, poor permeability, poor absorption, and rapid metabolism result in low oral bioavailability, which dramatically hinders their efficacy for use. Recently, free PTs have successively been found to self-assemble or co-assemble into self-contained nanostructures with enhanced water dispersibility and oral bioavailability, which seems to be an efficient processing method for increased oral efficacy. Of particular interest, formulating them into nanostructures can also be introduced as functional delivery carriers for bioactive compounds or drugs with various advantages, such as improved stability, controlled release, enhanced oral bioavailability, synergistic bioactivity, and targeted delivery. This review systematically summarized the chemical structures, plant sources, bioactivities, absorption, metabolism, and oral bioavailability of PTs. Notably, we emphasized their self-assembly properties and emerging role as functional delivery carriers for nutrients, suggesting that PT nanostructures are not only efficient oral forms when introduced into foods but also functional delivery materials for nutrients to expand their commercial food applications.

Carrier-free nanoplatforms from natural plants for enhanced bioactivity

BACKGROUND

Natural plants as well as traditional Chinese medicine have made outstanding contributions to the health and reproduction of human beings and remain the basis and major resource for drug innovation. Carrier-free nanoplatforms completely self-assembled by pure molecules or therapeutic components have attracted increasing attention due to their advantages of improved pharmacodynamics/pharmacokinetics, reduced toxicity, and high drug loading. In recent years, carrier-free nanoplatforms produced by self-assembly from natural plants have contributed to progress in a variety of therapeutic modalities. Notably, these nanoplatforms based on the interactions of components from different natural plants improve efficiency and depress toxicity.

AIM OF REVIEW

In this review, different types of self-assembled nanoplatforms are first summarized, mainly including nanoassemblies of pure small molecules isolated from different plants, extracellular vesicles separated from fresh plants, charcoal nanocomponents obtained from charred plants, and nanoaggregates from plants formulae decoctions. Key Scientific Concepts of Review: We mainly focus on composition, self-assembly mechanisms, biological activity and modes of action. Finally, a future perspective of existing challenges with respect to the clinical application of plant-based carrier-free nanoplatforms is discussed, which may be instructive to further develop effective carrier-free nanoplatforms from natural plants in the future.

Molecular Design, Supramolecular Assembly, and Excellent Dye Adsorption Capacity of Natural Rigid Dehydroabietic Acid-Tailored Amide Organogelators

It is very appealing to synthesize functional soft materials from natural and abundant plant diterpenes because they have conformationally rigid and chiral properties. Herein, dehydroabietic-based monoamide (DA-1) and diamide (DA-2) were designed by introducing device interactions, π-π stacking and hydrogen bonding, with an aromatic group, C═O, and N-H. DA-1 and DA-2 can be gelled in a mixed solvent and a single solvent, respectively. Several novel supramolecular organic gels including highly entangled three-dimensional networks composed of rods or fibers were constructed. Interestingly, DA-2 forms a helical structure that is right-handed under the cooperative control of the solvent and the rigid structure of rosin. Gel formation was primarily driven by hydrogen bonding, π-π stacking, and van der Waals force. Combined with Gaussian calculation and X-ray diffraction (XRD), we established pack patterns for each system, revealing the roles played by rosin and amide groups. Moreover, the carbon tetrachloride gel of DA-2 can effectively remove Congo red in an aqueous solution, and the removal rate can reach 98.4%. This research explores an efficient organic gel for adsorbing Congo red dye with the secretions of pine trees.

Supramolecular assemblies based on natural small molecules: Union would be effective

Natural products have been used to prevent and treat human diseases for thousands of years, especially the extensive natural small molecules (NSMs) such as terpenoids, steroids and glycosides. A quantity of studies are confined to concern about their chemical structures and pharmacological activities at the monomolecular level, whereas the spontaneous assemblies of them in liquids yielding supramolecular structures have not been clearly understood deeply. Compared to the macromolecules or synthetic small molecular compounds, NSMs have the inherent advantages of lower toxicity, better biocompatibility, biodegradability and biological activity. Self-assembly of single component and multicomponent co-assembly are unique techniques for designing supramolecular entities. Assemblies are of special significance due to their range of applications in the areas of drug delivery systems, pollutants capture, materials synthesis, etc. The assembled mechanism of supramolecular NSMs which are mainly driven by multiple non-covalent interactions are summarized. Furthermore, a new hypothesis aimed to interpret the integration effects of multi-components of traditional Chinese medicines (TCMs) inspired on the theory of supramolecular assembly is proposed. Generally, this review can enlighten us to achieve the qualitative leap for understanding natural products from monomolecule to supramolecular structures and multi-component interactions, which is valuable for the intensive research and application.

Phytonanomaterials as therapeutic agents and drug delivery carriers

Medicinal plants have been a major resource for drug discovery. Emerging evidence shows that in addition to pharmacologically active components, medicinal plants also contain phytochemical nanomaterials, or phytonanomaterials, which form nanoparticles for drug delivery. In this review, we examine the evidence supporting the existence of phytonanomaterials. Next, we review identification, isolation, and classification of phytonanomaterials, characteristics of phytonanomaterial-derived nanoparticles, and molecular mechanisms of phytonanomaterial assembly. We will then summarize the current progress in exploring phytonanomaterial-derived NPs as therapeutic agents and drug delivery carriers for disease treatment. Last, we will provide perspectives on future discovery and applications of phytonanomaterials.

A Close Look at Molecular Self-Assembly with the Transmission Electron Microscope

Molecular self-assembly is pervasive in the formation of living and synthetic materials. Knowledge gained from research into the principles of molecular self-assembly drives innovation in the biological, chemical, and materials sciences. Self-assembly processes span a wide range of temporal and spatial domains and are often unintuitive and complex. Studying such complex processes requires an arsenal of analytical and computational tools. Within this arsenal, the transmission electron microscope stands out for its unique ability to visualize and quantify self-assembly structures and processes. This review describes the contribution that the transmission electron microscope has made to the field of molecular self-assembly. An emphasis is placed on which TEM methods are applicable to different structures and processes and how TEM can be used in combination with other experimental or computational methods. Finally, we provide an outlook on the current challenges to, and opportunities for, increasing the impact that the transmission electron microscope can have on molecular self-assembly.

Preparation and Characterization of Oleanolic Acid-Based Low-Molecular-Weight Supramolecular Hydrogels Induced by Heating

The natural-product-based low-molecular-weight supramolecular hydrogels (LMWSHs) induced by heating are rarely reported. In this work, a simple salt of oleanolic acid (OA) and choline ([choline][OA]) was used as the natural product hydrogelator (NPHG) to form LMWSHs. Unlike common sol-gel transitions, the OA-based LMWSH displayed a unique property with which the system could undergo a phase transition from the sol state to the gel state upon heating. Moreover, the phase separation was observed in sol and gel states when the temperature was elevated with nonreversible transparent-turbid transitions. LMWSHs showed good stability and injectability and the potential to be a drug delivery vehicle for sustained release of drugs. In this regard, this work provided a facile approach to designing an OA-based NPHG for preparing heat-induced LMWSHs.

Natural pentacyclic triterpenoid acids potentially useful as biocompatible nanocarriers

The importance of natural raw materials has grown recently because of their ready availability, renewable nature, biocompatibility and controllable degradability. One such group of plant-derived substances includes the triterpenoid acids, terpenic compounds consisting of six isoprene units, a carboxyl group and other functional groups producing various isomers. Most can be easily extracted from different parts of the plant and modified successfully. By themselves or as aglycones (genins) of triterpene saponins, they have potentially useful pharmaceutical activity. This review focuses on the supramolecular properties of triterpenoid acids with regard to their subsequent use as biocompatible nanocarriers. The review also considers the current list of pentacyclic triterpene acids for which molecular self-assembly has been confirmed without the need for structural modification.

Plumeria rubra L.- A review on its ethnopharmacological, morphological, phytochemical, pharmacological and toxicological studies

ETHNOPHARMACOLOGICAL RELEVANCE

Plumeria rubra L. (Apocynaceae) is a deciduous, commonly ornamental, tropical plant grown in home premises, parks, gardens, graveyards, because of its beautiful and attractive flowers of various colours and size. The different parts of the plant are used traditionally to treat various diseases and conditions like leprosy, inflammation, diabetic mellitus, ulcers, wounds, itching, acne, toothache, earache, tongue cleaning, pain, asthma, constipation and antifertility.

AIM OF THE REVIEW

The main aim of this review is to provide an overview and critically analyze the reported ethnomedical uses, phytochemistry, pharmacological activities and toxicological studies of P. rubra and to identify the remaining gaps and thus supply a basis for further investigations. The review also focuses towards drawing attention of people and researchers about the wide spread pharmaceutical properties of the plant for its better utilization in the coming future.

MATERIAL AND METHODS

All the relevant data and information on P. rubra was gathered using various databases such as PubMed, Springer, Taylor and Francis imprints, NCBI (National Center for Biotechnology Information), Science direct, Google scholar, Chemspider, SciFinder, research and review articles from peer-reviewed journals and unpublished data such as Phd thesis, etc. Some other 'grey literature' sources such as webpages, ethnobotanical books, chapters, wikipedia were also studied.

RESULTS

More than 110 chemical constituents have been isolated from P. rubra including iridoids, terpenoids, flavonoids and flavonoid glycosides, alkaloids, glycosides, fatty acid esters, carbohydrates, animo acids, lignan, coumarin, volatile oils, etc. The important chemical constituents responsible for pharmacological activities of the plant are fulvoplumierin, plumieride, rubrinol, lupeol, oleanolic acid, stigmasterol, taraxasteryl acetate, plumieride-p-E-coumarate, rubranonoside, rubrajalellol, plumericin, isoplumericin, etc. The plant possess a wide range of pharmacological activities present namely antibacterial, antiviral, anti-inflammatory, antipyretic, antidiabetic, hepatoprotective, anticancer, anthelmintic, antifertility and many other activities.

CONCLUSION

P. rubra is a valuable medicinal source and further study in this topic can validate the traditional and ethnobotanical use of the plant. However, many aspects of the plant have not been studied yet. The pharmacological activity of active chemical constituent isolated from the plant is proven only for a couple of activities hence, lack of bio-guided isolation strategies is observed. Further studies on bioavailability, pharmacokinetics, mechanism of action and structural activity relationship studies of isolated pure compounds will contribute more in understanding their pharmacological effects. Higher doses of plant extracts are administered to experimental animals, therefore their toxicity and side effects in humans are needed to be thoroughly studied, although no side effect or toxicity is seen or observed in experimental animals. Studies are also essential to investigate the long term in vivo toxicity and clinical efficacy of the plant.

Flower- and Grass-like Self-Assemblies of an Oleanane-Type Triterpenoid Erythrodiol: Application in the Removal of Toxic Dye from Water

Erythrodiol (3β-olean-12-ene-3, 28-diol) (C30H50O2) 1 is a nanosized oleanane-type fused 6-6-6-6-6 pentacyclic triterpeneoid extractable from the dried leaves of olive (Olea europia). One step reduction of oleanolic acid extracted from Lantana camara also yields the same compound. The triterpenoid has one secondary -OH group attached at C3 of the "A" ring and one primary -OH group at C28 present at the junction of the "D" and "E" rings. Here, we report the spontaneous self-assembly of erythrodiol in different neat organic liquids and aqueous-organic liquid mixtures. The nanosized dihydroxy triterpenoid having an oleanane-type lipophilic rigid skeleton self-assembled in liquids, yielding nanosized fibrils, microsized flowers, and grass-like architectures via formation of densely assembled fibrils and petals or 2D sheets. The microstructures of the self-assemblies have been characterized by different techniques like optical microscopy, electron microscopy, atomic force microscopy, FTIR, and wide angle X-ray diffraction studies. The porous self-assemblies having a large surface area obtained from 1 were capable of adsorbing toxic fluorophores like rhodamine-B, rhodamine-6G, methylene blue, and crystal violet (CV). Moreover, removal of the aforementioned toxic pigments has also been demonstrated from their aqueous solutions by using UV-visible spectrophotometry and epifluorescence microscopy.

Self-assembled small molecule natural product gel for drug delivery: a breakthrough in new application of small molecule natural products

Natural products, as a gift of nature to humanity, have long been used as drugs or pharmacological actives to help people cure various diseases. Yet we still know comparatively little about their ability to be materials. In recent years, some small molecule natural products isolated from traditional Chinese medicines have been found to have new features, namely, self-assembly to form gels (i.e., natural product gels, NPG). However, the application development of these natural products is seriously lacking, which greatly weakens their practical value and delays the maturity of the field. Here, a series of self-assembled triterpenoid natural products are used as materials (gel scaffolds) to construct drug delivery systems. Surprisingly, these NPG not only exhibit the excellent self-healing, controlled gelation, good safety and sustained release, but also achieve synergistic treatment of tumors through bioactive natural products. Compared with non-bioactive gel scaffolds, NPG scaffolds show great advantages in tumor therapy, including optimal tumor inhibition, preferable health, better body recovery, stronger immune function, less toxic side effects and longer survival. The successful construction of NPG scaffolds not only takes full advantage of the self-assembled natural products, but also takes an important step in the development of new applications for natural products.

Terpenoids, nano-entities and molecular self-assembly

Plant metabolites being renewable in nature have tremendous significance for the development of a sustainable society. In this manuscript we show that, terpenoids having nanometric lengths, commonly having several functional groups and several centers of chirality, can be utilized as renewable Molecular Functional Nanos (MFNs). The terpenoids spontaneously self-assembled in liquids yielding different morphologies such as vesicles, tubes, flowers, petals and fibers of nano- to micro-meter dimensions and supramolecular gels. The self-assemblies were utilized for the entrapment and release of fluorophores including anticancer drug, pollutant capture, generation of hybrid materials and catalysis.

Exploration of the Natural Active Small-Molecule Drug-Loading Process and Highly Efficient Synergistic Antitumor Efficacy

The development and application of nano-drug carriers might provide an excellent opportunity for cancer therapy. However, it is still an important challenge to realize the regulation and control of drug loading by analyzing the assembly process of carrier-loaded drugs. Herein, we show a "self-contained bioactive nanocarrier" system, which is prepared from ursolic acid, one of the very promising biologically active natural products with self-assembly properties. The study decrypts the assembly process of drug-carrier interaction and achieves the regulation of drug loading by controlling the interaction force. This nanocarrier highlights the unique advantages of active natural products in therapeutic efficacy and health benefits. In antitumor experiments, the carrier and drug demonstrated synergistic therapeutic efficacy. Furthermore, the nanocarrier is biosafe and capable of reducing the risk of liver damage induced by chemotherapeutics through the upregulation of key antioxidant pathways. Taken together, this "self-contained bioactive nanocarrier" system makes up for the drawback that conventional nanocarriers have no therapeutic efficacy and health benefits and eliminates the trouble of the toxic side effects associated with chemotherapy agents and the additional toxicity caused by long-term use of nanocarriers.

Vesicular self-assembly of a natural ursane-type dihydroxy-triterpenoid corosolic acid

Corosolic acid, a natural ursane-type 6-6-6-6-6 pentacyclic dihydroxy triterpenic acid, is a well known antidiabetic compound extractable from leaves of Psidium guajava. In this manuscript we have reported the self-assembly properties of corosolic acid in different liquids. The compound undergoes self-assembly to give vesicular morphology in different aqueous organic liquids. Supramolecular gels were also obtained in some aqueous binary liquids such as ethanol–water and dimethyl formamide–water. The morphology of the self-assemblies of corosolic acid were characterized by using different microscopic techniques like optical microscopy, field emission scanning electron microscopy, transmission electron microscopy, atomic force microscopy as well as XRD and FTIR studies. We also demonstrated the application of vesicular self-assemblies for the entrapment and release of fluorophores including an anticancer drug.

Corosolic acid, a natural ursane-type 6-6-6-6-6 pentacyclic dihydroxy triterpenic acid, self-assembled in binary liquid mixtures yielding vesicles.

Green synthesis of Nerium oleander-conjugated gold nanoparticles and study of its in vitro anticancer activity on MCF-7 cell lines and catalytic activity

The phytochemicals present in the stem bark extract of Nerium oleander (commonly known as Karabi) have been utilized for the green synthesis of stable gold-conjugated nanoparticles at room temperature under very mild conditions. The green synthesized gold-conjugated nanoparticles were characterized by surface plasmon resonance spectroscopy, High resolution transmission electron microscopy, X-ray diffraction studies and dynamic light scattering. A mechanism for the synthesis and stabilization of gold-conjugated nanoparticles (AuNPs) has been proposed. Anticancer activity of the stabilized AuNPs studied against MCF-7 breast cancer cell line revealed that the stabilized AuNPs were highly effective for the apoptosis of cancer cells selectively. The antioxidant activity of the stem bark extract of Nerium oleander has also been studied against a long lived 2,2-diphenylpicrylhydrazyl radical at room temperature. Moreover, the utilization of the stabilized AuNPs as a catalyst has also been demonstrated.

Natural product gelators and a general method for obtaining them from organisms

Since the late 1980s, low molecular weight gelators (LMWGs) based on different classes of natural products have been reported. Until 2011, pure natural LMWGs (i.e., natural product gelators, NPGs) were not found. However, today only five NPGs are reported. We think that this may be due to the lack of awareness about the importance of NPGs and suitable methods to discover new NPGs. Here we illustrate the potential significance of NPGs, and present a general and efficient method for obtaining NPGs from organisms, which provides specific and important guidance to researchers for easy discovery of new NPGs from organisms in the future. Using this method, we screened a total of 64 kinds of organisms (including plants, animals and fungi), and 6 extracts with a gelation ability were tracked and isolated to yield six new NPGs. These new NPGs include new types of NPGs such as tricyclic triterpenes (1) and tetracyclic triterpenes (2), and new classes of NPGs such as steroids (4 and 5) and glycosides (6), which greatly expand the class of NPGs in the LMWG field.

Self-assembled fibrillar networks induced by two methods: a new unmodified natural product gel

The discovery of new NPGs and the study of their self-assembing properties.

First in situ vesicular self-assembly of ‘binols’ generated by a two-component aerobic oxidation reaction

Generation of vesicular self-assemblies from natural and synthetic components has been in the frontiers of research in recent years for an improved understanding of the self-assembly process and also because of its prospective and realized applications in the areas of advanced materials, biotechnology and medicine. In the present work, we report the first example of the in situ generation of vesicular self-assemblies during an aerobic coupling reaction. The two precursor 2-naphthol units, having hydrogen bond donor–acceptor groups with appended alkyl chains, yielded binol (2,2′-dihydroxy-1,1′-binaphthyl) derivatives by aerobic coupling that spontaneously self-assembled in situ, yielding vesicular self-assemblies and gels. The morphology of the self-assemblies has been characterized by various optical, electron and atomic force microscopic techniques. The vesicular self-assemblies obtained in the liquids were capable of entrapping fluorophores such as rhodamine-B and carboxy fluorescein including the anticancer drug doxorubicin. The entrapped fluorophores could also be released by sonication or by rupture of vesicles. The supramolecular gels obtained in binary solvent mixtures showed improved gelation abilities with increase in the alkyl chain lengths as reflected by their minimum gelator concentration (mgcs) values, gel to sol transition temperatures (T_gel) and rheology properties. The results described here are also the first demonstration of gelation during an aerobic coupling reaction.

Binol derivatives, obtained by aerobic coupling of two 2-naphthol derivatives having H-bond donor–acceptor groups and appended alkyl chains, spontaneously self-assembled in situ yielding vesicular self-assemblies and gels.

Spontaneous catanionic vesicles formed by the interaction between an anionic β-cyclodextrins derivative and a cationic surfactant

The present work shows the synthesis of a new type of catanionic surfactant, ModCD14–BHD, which involves an anionic amphiphilic cyclodextrin and the cationic benzyl-n-hexadecyldimethylammonium (BHD). It is obtained from the simple association of the cationic surfactant benzyl-n-hexadecyldimethylammonium chloride (BHDC) and β-cyclodextrin (β-CD) monosubstituted with an alkenyl succinate group (Mod-β-CD14). ModCD14–BHD form unilamellar vesicles spontaneously in water, while the individual components (BHDC and Mod-β-CD14) do not. The vesicles were character-ized by dynamic light scattering (DLS), transmission electron microscopy (TEM), scanning electron microscopy (SEM) and ¹H NMR techniques. We suggest that the formation of an inclusion complex between some of the cyclodextrins units and the long hydrocarbon moiety of the cationic surfactant play a crucial role in the vesicles formation. Besides, some or the cavities are available to interact with an external guest. We think that the new surfactant molecule has properties that may lead to important applications in biomedical and pharmaceutical sciences.

Catanionic vesicles containing an anionic β-cyclodextrins derivative and a cationic surfactant.