Triterpenoid Building Blocks for Functional Nanoscale Assemblies: A Review

Abstract

Naturally abundant, renewable, and sustainable plant triterpenoids have gained considerable attention in biological application, including antitumor activities. However, due to their lipophilic nature, natural triterpenoids display limited solubility in aqueous media. Notably, the rigid backbone and the presence of functional groups also offer the possibilities toward a strategic design of a class of conformationally rigid amphiphiles. Such derivatives may improve their bioavailability, and they display unique self-assembly properties relevant for soft functional materials. In recent years, a formation of nano-assemblies has been studied with plant triterpenoids and their semisynthetic derivatives to investigate ways of their applications in materials science. For example, naturally amphiphilic glycyrrhizic acid has been shown to form hydrogels. Similarly, other natural triterpenoid-based phosphates or heterocyclic-based quaternary conjugates have also been studied for supramolecular gelation. Triterpenoid-based supramolecular gels are important types of soft materials, displaying rapid self-healing, thixotropic behaviors, aging-induced transition, and self-assemblyinduced anticancer and antimicrobial properties. In this review, we will provide a summary of (i) unique structural and functional properties of natural triterpenoids, (ii) self-assembly and gelation properties of natural triterpenoids, (iii) gelation properties of rationally designed triterpenoid derivatives, (iv) structural transition in aqueous media, and (v) their biological effects.

Saponins of Selected Triterpenoids as Potential Therapeutic Agents: A Review

“…It is expected that the number of practically successful triterpenoid derivatives will gradually increase. Our recent results dealing with different derivatives of plant triterpenoids, not including their glycoconjugates, displayed the high potential of these compounds as antimicrobial, antiviral, and cytotoxic agents [ 26 , 27 , 28 ]. Some of them showed their capability of acting as chemodynamic and photodynamic therapy agents [ 80 , 81 ] or coordinating metal ions, such as radioisotopic 64 Cu(II) salts, for potential positron emission tomography (PET) imaging and radiotherapy in combination with cytotoxicity [ 27 ].…”

“…Some of them showed their capability of acting as chemodynamic and photodynamic therapy agents [ 80 , 81 ] or coordinating metal ions, such as radioisotopic 64 Cu(II) salts, for potential positron emission tomography (PET) imaging and radiotherapy in combination with cytotoxicity [ 27 ]. Due to the important potential of plant triterpenoids and their semisynthetic derivatives, they have been intensively studied as functional nanoscale assemblies with an impact in the areas of nanomedicine and drug delivery, but also in dye removal or catalysis in different chemical processes, and this importance will be even increasing in the forthcoming time [ 28 ].…”

“…Self-assembly was also observed with other natural products, e.g., sterols and their derivatives, including derivatives of steryl saponins [ 23 ]. Later on, different derivatives of natural triterpenoids have also been subjected to a similar investigation resulting in the findings that a number of those compounds also display the analogous ability to self-assemble, and the formed nanosized materials exhibited important physicochemical and pharmacological characteristics, making those triterpenoid-based materials attractive for a more detailed investigation of their physicochemical properties and pharmacological effects [ 24 , 25 , 26 , 27 , 28 ]. Nanosized materials of this origin often display amphiphilic properties, which are important for pharmacological and medicinal applications.…”

Precision nanoengineering for functional self-assemblies across length scales

“…In molecular-level building blocks, conformationally rigid surfactants have been shown to display similar self-assembly patterns to that of peptides. 105 Importantly, the rigid surfactants and peptides are chemically dissimilar, still producing similar structures. Similarly, identifying the structural features in nanoparticle building blocks that mimic virus capsid proteins and capsids may offer routes for precision structures other than routinely observed 3D crystals.…”

Nano-assembly of cytotoxic amides of moronic and morolic acid

“…Plant triterpenoids and their derivatives have been studied for their self-assembly behaviour mainly in organic solvents, 18,19 while studies under aqueous conditions have been quite rare so far. 11,19 Due to the rigid backbone of triterpenoids, their conjugates have been attractive candidates for designing a new class of conformationally rigid amphiphiles. 11,18,19…”