Synthesis, anticancer evaluation and mechanism studies of novel indolequinone derivatives of ursolic acid

Potential Pharmacological Properties of Triterpene Derivatives of Ursolic Acid

Ursolic acid (UA) and its derivatives have garnered significant attention due to their extensive pharmacological activity. UA is a pentacyclic triterpenoid found in a variety of plants, such as apples, rosemary, thyme, etc., and it possesses a range of pharmacological properties. Researchers have synthesized various derivatives of UA through structural modifications to enhance its potential pharmacological properties. Various in vitro and in vivo studies have indicated that UA and its derivatives possess diverse biological activities, such as anticancer, antifungal, antidiabetic, antioxidant, antibacterial, anti-inflammatory and antiviral properties. This review article provides a review of the biological activities of UA and its derivatives to show their valuable therapeutic properties useful in the treatment of different diseases, mainly focusing on the relevant structure-activity relationships (SARs), the underlying molecular targets/pathways, and modes of action.

An Update on Pentacyclic Triterpenoids Ursolic and Oleanolic Acids and Related Derivatives as Anticancer Candidates

Cancer is a global health problem, with the incidence rate estimated to reach 40% of the population by 2030. Although there are currently several therapeutic methods, none of them guarantee complete healing. Plant-derived natural products show high therapeutic potential in the management of various types of cancer, with some of them already being used in current practice. Among different classes of phytocompounds, pentacyclic triterpenoids have been in the spotlight of research on this topic. Ursolic acid (UA) and its structural isomer, oleanolic acid (OA), represent compounds intensively studied and tested in vitro and in vivo for their anticancer and chemopreventive properties. Since natural compounds can rarely be used in practice as such due to their characteristic physico-chemical properties, to tackle this problem, their derivatization has been attempted, obtaining compounds with improved solubility, absorption, stability, effectiveness, and reduced toxicity. This review presents various UA and OA derivatives that have been synthesized and evaluated in recent studies for their anticancer potential. It can be observed that the most frequent structural transformations were carried out at the C-3, C-28, or both positions simultaneously. It has been demonstrated that conjugation with heterocycles or cinnamic acid, derivatization as hydrazide, or transforming OH groups into esters or amides increases anticancer efficacy.

Novel MeON-glycosides of ursolic acid: Synthesis, antitumor evaluation, and mechanism studies

Ursolic acid (UA) is a pentacyclic triterpenoid widely found in in medicinal plants, edible plants, fruits, and flowers. The great interest in this bioactive compound is related to the positive effects in human health. However, its limited solubility, moderate biological activity and poor bioavailability limit the potential and further applications of UA. Here, we explored the efficacy of MeON-Glycosides of UA in inhibiting tumor cell proliferation. A number of compounds showed significant antitumor activity against tested five cancer cell lines. Among them, compound 2a exhibited the most potent activity against HepG2 cells with IC50 values of 3.1 ± 0.5 μM. Especially, compound 2a could induce HepG2 cells apoptosis and reduce mitochondrial membrane potential. Western blot analysis showed that compound 2a up-regulated Bax, cleaved caspase-3/9, cleaved PARP levels and down-regulated Bcl-2 level of HepG2 cells. These results indicated that compound 2a could obviously induce the apoptosis of HepG2 cells. At the same time, compound 2a significantly decreased the expression of p-AKT and p-mTOR, which indicated that compound 2a might exert its cytotoxic effect by targeting PI3K/AKT/mTOR signaling pathway. Moreover, the in silico ADME predictions showed that compound 2a has improved water solubility and other properties. Thus, compound 2a may be a promising antitumor candidate, which may be potentially used to prevent or treat cancers.

Discovery of Novel Pentacyclic Triterpene Acid Amide Derivatives as Excellent Antimicrobial Agents Dependent on Generation of Reactive Oxygen Species

Developing new agricultural bactericides is a feasible strategy for stopping the increase in the resistance of plant pathogenic bacteria. Some pentacyclic triterpene acid derivatives were elaborately designed and synthesized. In particular, compound A₂₂ exhibited the best antimicrobial activity against Xanthomonas oryzae pv. oryzae (Xoo) and Xanthomonas axonopodis pv. citri (Xac) with EC₅₀ values of 3.34 and 3.30 mg L^-1, respectively. The antimicrobial mechanism showed that the compound A₂₂ induced excessive production and accumulation of reactive oxygen species (ROS) in Xoo cells, leading to a decrease in superoxide dismutase and catalase enzyme activities and an increase in malondialdehyde content. A₂₂ also produced increases in Xoo cell membrane permeability and eventual cell death. In addition, in vivo experiments showed that A₂₂ at 200 mg L^-1 exhibited protective activity against rice bacterial blight (50.44%) and citrus canker disease (84.37%). Therefore, this study provides a paradigm for the agricultural application of pentacyclic triterpene acid.

Ursolic Acid Analogs as Potential Therapeutics for Cancer

Ursolic acid (UA) is a pentacyclic triterpene isolated from a large variety of vegetables, fruits and many traditional medicinal plants. It is a structural isomer of Oleanolic Acid. The medicinal application of UA has been explored extensively over the last two decades. The diverse pharmacological properties of UA include anti-inflammatory, antimicrobial, antiviral, antioxidant, anti-proliferative, etc. Especially, UA holds a promising position, potentially, as a cancer preventive and therapeutic agent due to its relatively non-toxic properties against normal cells but its antioxidant and antiproliferative activities against cancer cells. Cell culture studies have shown interference of UA with multiple pharmacological and molecular targets that play a critical role in many cells signaling pathways. Although UA is considered a privileged natural product, its clinical applications are limited due to its low absorption through the gastro-intestinal track and rapid elimination. The low bioavailability of UA limits its use as a therapeutic drug. To overcome these drawbacks and utilize the importance of the scaffold, many researchers have been engaged in designing and developing synthetic analogs of UA via structural modifications. This present review summarizes the synthetic UA analogs and their cytotoxic antiproliferative properties reported in the last two decades.

New Betulin Derivatives with Nitrogen Heterocyclic Moiety-Synthesis and Anticancer Activity In Vitro

As part of the search for new medicinal substances with potential application in oncology, the synthesis of new compounds combining the betulin molecule and the indole system was carried out. The structure of the ester derivatives obtained in the Steglich reaction was confirmed by spectroscopic methods (¹H and ¹³C NMR, HR-MS). The obtained new 3-indolyl betulin derivatives were evaluated for anticancer activity against several human cancer cell lines (melanomas, breast cancers, colorectal adenocarcinomas, lung cancer) as well as normal human fibroblasts. The significant reduction in MCF-7 cells viability for 28-hydroxy-(lup-20(29)-ene)-3-yl 2-(1H-indol-3-yl)acetate was observed at a concentration of 10 µg/mL (17 µM). In addition, cytometric analysis showed that this compound strongly reduces the proliferation rate of breast cancer cells. For this, the derivative showing the promising cytotoxic effect on MCF-7 breast cancer cells, the pharmacokinetic profile prediction was performed using in silico methods. Based on the results obtained in the study, it can be concluded that indole-functionalized triterpene EB367 is a promising starting point for further research in the field of breast cancer therapy or the synthesis of new derivatives.

The in vitro and in vivo study of oleanolic acid indole derivatives as novel anti-inflammatory agents: Synthesis, biological evaluation, and mechanistic analysis

Oleanolic acid (OA) is a well-known natural product possessing many important pharmacological activities; however, its weak bioactivities significantly restrict the potential application in drug development. The structural modification of oleanolic acid is an effective mean to enhance its bioactivity with lower toxicity but it is challenging. In the present study, we systematically synthesized a series of new 11-oxooleanolic acid derivatives and evaluated their anti-inflammatory activities with a LPS induced BV2 cells inflammation model and a 12-O-tetradecanoyl phorbol-13-acetate (TPA) induced ear inflammation mice model. It was found that compounds 8 and 9 show more potent anti-inflammatory effects than OA and exhibit a low cytotoxicity. The possible mechanism of action was also investigated. The in vitro and in vivo results revealed that these two new 11-oxooleanolic acid derivatives may exert anti-inflammatory activities through the inhibition of NO, pro-inflammatory cytokines and chemokines (IL-1β, IL-6, IL-12, TNF-α, MCP-1 and MIP-1α) and upregulation of anti-inflammatory cytokines (IL-10), which may be caused by inhibiting the activation of NF-κB, MAPKs and PI3K/Akt related inflammatory signaling pathways and the activation of Nrf2/HO-1 signaling pathway. The results suggest that these two 11-oxooleanolic acid derivatives may be potential candidates for further anti-inflammatory drug development and our study demonstrated an important and practical strategy for drug discovery through the rational modification of natural products.