Recent Progress in Oleanolic Acid: Structural Modification and Biological Activity

Nanostructures in Chinese herbal medicines (CHMs) for potential therapy

With its long clinical history, traditional Chinese medicine (TCM) has gained acceptance for its specific efficacy and safety in the treatment of multiple diseases. Nano-sized materials study of Chinese herbal medicines (CHMs) leads to an increased understanding of assessing TCM therapies, which may be a promising way to illustrate the material basis of CHMs through their processing and extraction. In this review, we provide an overview of the nanostructures of natural and engineered CHMs, including extracted CHMs, polymer nanoparticles, liposomes, micelles, and nanofibers. Subsequently, the applications of these CHM-derived nanostructures to particular diseases are summarized and discussed. Additionally, we discuss the advantages of these nanostructures for studying the therapeutic efficacy of CHMs. Finally, the key challenges and opportunities for the development of these nanostructures are outlined.

Curcumin-Triterpene Type Hybrid as Effective Sonosensitizers for Sonodynamic Therapy in Oral Squamous Cell Carcinoma

Sonodynamic therapy (SDT) is a non-invasive therapeutic modality in cancer treatment that combines low-intensity ultrasound (US) and sonosensitizers. Tumor cells are destroyed through the synergistic effects of ultrasound and a chemical sonosensitizer. This study focused on the synthesis and in vitro evaluation of the sonodynamic effect of natural curcumin, triterpene oleanolic acid, and their semi-synthetic derivatives on tongue cancer SCC-25 and hypopharyngeal FaDu cell lines. The combination of the tested compounds with sonication showed a synergistic increase in cytotoxicity. In the group of oleanolic acid derivatives, oleanoyl hydrogen succinate (6) showed the strongest cytotoxic effect both in the SCC-25 and FaDu cell lines. Comparing curcumin (4) and its pyrazole derivative (5), curcumin showed a better cytotoxic effect on SCC-25 cells, while curcumin pyrazole was more potent on FaDu cells. The highest sonotherapeutic activity, compared to its individual components, was demonstrated by a structural linker mode hybrid containing both curcumin pyrazole-oleanoyl hydrogen succinate units within one complex molecule (7). This study can be beneficial in the context of new perspectives in the search for effective sonosensitizers among derivatives of natural organic compounds.

Synthesis of Oleanolic Acid-Dithiocarbamate Conjugates and Evaluation of Their Broad-Spectrum Antitumor Activities

Efficient and mild synthetic routes for bioactive natural product derivatives are of current interest for drug discovery. Herein, on the basis of the pharmacophore hybrid strategy, we report a two-step protocol to obtain a series of structurally novel oleanolic acid (OA)-dithiocarbamate conjugates in mild conditions with high yields. Moreover, biological evaluations indicated that representative compound 3e exhibited the most potent and broad-spectrum antiproliferative effects against Panc1, A549, Hep3B, Huh-7, HT-29, and Hela cells with low cytotoxicity on normal cells. In terms of the IC₅₀ values, these OA-dithiocarbamate conjugates were up to 30-fold more potent than the natural product OA. These compounds may be promising hit compounds for the development of novel anti-cancer drugs.

Synthesis, Anti-Influenza H1N1 and Anti-Dengue Activity of A-Ring Modified Oleanonic Acid Polyamine Derivatives

A series of sixteen A-ring modified (2,3-indolo-, 2-benzylidene) oleanonic acid derivatives, holding some cyclic amines, linear polyamines and benzylaminocarboxamides at C28, has been synthesized and screened for antiviral activity against influenza A/PuertoRico/8/34 (H1N1) and Dengue virus serotypes of DENV-1, -2, -3, -4. It was found that 28-homopiperazine 2 and 3-N-phthalyl 22 amides of oleanonic acid demonstrated high potency with selectivity index SI 27 (IC₅₀ 21 μM) and 42 (IC₅₀ 12 μM). Oleanonic acid aminoethylpiperazine amide 6 and C-azepano-erythrodiol 23 appeared to be the most effective compounds against DENV-1 (IC_50's 67 and 107 μM) and -2 (IC_50's 86 and 68 μM correspondingly) serotypes.

Natural Product-Inspired Targeted Protein Degraders: Advances and Perspectives

Targeted protein degradation (TPD), a promising therapeutic strategy in drug discovery, has great potential to regulate the endogenous degradation of undruggable targets with small molecules. As vital resources that provide diverse structural templates for drug discovery, natural products (NPs) are a rising and robust arsenal for the development of therapeutic TPD. The first proof-of-concept study of proteolysis-targeting chimeras (PROTACs) was a natural polyketide ovalicin-derived degrader; since then, NPs have shown great potential to promote TPD technology. The use of NP-inspired targeted protein degraders has been confirmed to be a promising strategy to treat many human conditions, including cancer, inflammation, and nonalcoholic fatty liver disease. Nevertheless, the development of NP-inspired degraders is challenging, and the field is currently in its infancy. In this review, we summarize the bioactivities and mechanisms of NP-inspired degraders and discuss the associated challenges and future opportunities in this field.

Insights into isostructural and non-isostructural crystals of esters of oleanolic acid and its 11-oxo derivatives

Synthesis and structural characterization of new esters of oleanolic acid and its 11-oxo derivatives are reported. Compounds crystallize in four isostructural groups, each containing one to four structures. Single-crystal X-ray analysis revealed that molecules belonging to non-isostructural groups self-associate according to two schemes that describe also supramolecular architectures in crystals of glycyrrhetinic acid derivatives. Structural motifs arise as a result of van der Waals forces. Parameters introduced for the analysis of one- and two-dimensional assemblies allow the comparison of motifs in isostructural and non-isostructural crystals, including polymorphs, and a qualitative assessment of differences in molecular self-assembly. One-, two- or three-dimensional similarity has been confirmed by XPac calculations.