Triterpenoids

Kaguacidine A: a novel spirohydantoin-containing cucurbitane glycoside from vines of Momordica charantia L

The spirohydantoin-containing cucurbitane-type triterpenoid, kaguacidine A (1), was isolated and purified from 95% ethanol extract of vines of Momordica charantia L. (Cucurbitaceae). Its unprecedented chemical structure, a spirohydantoin substituent at C-23 of cucurbitane, was elucidated by extensive spectroscopic analyses, including HRESIMS, IR, optical rotation, 1 D- and 2 D-NMR spectra. The possible biosynthetic pathway is deduced and may be attributed to the metabolic activity of microbial symbionts in M. charantia L. Compound 1 was evaluated for anti-inflammatory activity against LPS-induced NO production in RAW 264.7 cells and anti-proliferative activity against four cancer cell lines, including HEp-2, MCF-7, Hep-G2, and WiDr. Compound 1 showed moderate anti-inflammatory activity with an IC50 value of 18.5 ± 0.4 μg/mL and weak anti-proliferative activity against MCF-7, HEp-2, Hep-G2, and WiDr with IC50 values of >40, 33.8 ± 0.6, 31.0 ± 0.7, and 27.0 ± 0.7 μM, respectively.

Extraction, purification and anticancer activity studies on triterpenes from pomegranate peel

Pomegranate peel is the by-product of pomegranate processing, which contains a lot of triterpene compounds. In this study, the total triterpenes of pomegranate peel (TPP) were extracted using an ultrasonic-assisted ethanol extraction method under optimal conditions, purified using D-101 macroporous resin to obtain a purity of 75.28%. The triterpenes in TPP were mainly pentacyclic triterpenes determined by LC-MS/MS. Network pharmacological analysis predicted that the anticancer targets were closely related to the MAPK pathway. The in vitro results showed that TPP could inhibit cell proliferation, promote apoptosis, reduce mitochondrial membrane potential and increase ROS levels. The western blot results indicated that the expression levels of the apoptotic proteins Bax, Bcl-2, cytochrome C, cleaved caspase-3 and cleaved caspase-9 were increased. In addition, the protein expression of the MAPK pathway predicted by network pharmacology also changed significantly. These results provided that TPP has potential for adjuvant therapy of tumors.

Naturally Occurring Norsteroids and Their Design and Pharmaceutical Application

The main focus of this review is to introduce readers to the fascinating class of lipid molecules known as norsteroids, exploring their distribution across various biotopes and their biological activities. The review provides an in-depth analysis of various modified steroids, including A, B, C, and D-norsteroids, each characterized by distinct structural alterations. These modifications, which range from the removal of specific methyl groups to changes in the steroid core, result in unique molecular architectures that significantly impact their biological activity and therapeutic potential. The discussion on A, B, C, and D-norsteroids sheds light on their unique configurations and how these structural modifications influence their pharmacological properties. The review also presents examples from natural sources that produce a diverse array of steroids with distinct structures, including the aforementioned A, B, C, and D-nor variants. These compounds are sourced from marine organisms like sponges, soft corals, and starfish, as well as terrestrial entities such as plants, fungi, and bacteria. The exploration of these steroids encompasses their biosynthesis, ecological significance, and potential medical applications, highlighting a crucial area of interest in pharmacology and natural product chemistry. The review emphasizes the importance of researching these steroids for drug development, particularly in addressing diseases where conventional medications are inadequate or for conditions lacking sufficient therapeutic options. Examples of norsteroid synthesis are provided to illustrate the practical applications of this research.

An unexpected conversion of 2E-furfurylidene-3-oxo-24-nor-allobetulin to 23-nor-allobetulins

A series of 2E-furfurylidene-23-nor- and 24-nor-allobetulins has been synthesized by the Claisen-Schmidt condensation and conditions of their formation were studied in detail. It was found that among an expected 2E-furfurylidene-3-oxo-24-nor-allobetulin 4 two byproducts holding 3-oxo-4α-hydroxy- 5 and 3β,4α-dihydroxy- 6 substituents were formed, which could become the main products under the change of reaction time and amount of the base solution. Moreover, a conversion of individual 2E-furfurylidene-23-nor-3-oxo-4α-hydroxy- 5 into 2E-furfurylidene-23-nor-3β,4α-dihydroxy-derivative 6 under the treatment with the base solution was observed. An inversion of the configuration at C4 from 24-nor- to 23-nor-allobetulins for compounds 5 - 7 was proved by the NMR spectra. The probable explanation of compound 5 formation includes oxidation by atmospheric oxygen to 4-hydroperoxide, which was further transformed into 4-hydroxy-group. In the presence of the base the reduction C3(=O)-function of compound 5 occurs like Meerwein- Ponndorf-Verley reaction to give compound 6. As a result, a difference in the reactivity of native allobetulin scaffold and 24-nor-allobetulin in the Claisen-Schmidt condensation was observed and a first case of conversion 24-nor- to 23-nor-allobetulin derivatives was described.

Design and synthesis of novel hederagonic acid analogs as potent anti-inflammatory compounds capable of protecting against LPS-induced acute lung injury

Acute lung injury (ALI) presents a significant clinical challenge due to its high mortality rates and the lack of effective treatment strategies. The most effective approaches to treating ALI include disrupting inflammatory cascades and associated inflammatory damage within the lung. Hederagenin was utilized as a core skeleton to design and synthesize 33 hederagonic acid derivatives. Among these derivatives, compound 29 demonstrated potent anti-inflammatory activity without inducing cytotoxicity, inhibiting nitric oxide (NO) release by 78-86 %. Detailed structure-activity relationship studies and the reverse virtual screening of ALI-related targets revealed that compound 29 exhibits a high affinity for the STING protein. Mechanistic studies revealed that compound 29 suppresses macrophage activation, inhibits the nuclear translocation of IRF3 and p65, and disrupts the STING/IRF3/NF-κB signaling pathway, thereby attenuating the inflammatory response. The in vivo administration of compound 29 was sufficient to protect against lipopolysaccharide (LPS)-induced ALI by suppressing the production of inflammatory mediators, including IL-6, TNF-α, and IFN-β, thereby preserving lung tissue integrity. These results substantiate the anti-inflammatory efficacy of compound 29, both in vitro and in vivo, indicating its potential as a promising lead compound in ALI treatment strategies.

An updated review of the genus Rhododendron since 2010: Traditional uses, phytochemistry, and pharmacology

Rhododendron, the largest genus of Ericaceae, consists of approximately 1000 species that are widely distributed in Europe, Asia, and North America but mainly exist in Asia. Rhododendron plants have not only good ornamental and economic value but also significant medicinal potential. In China, many Rhododendron plants are used as traditional Chinese medicine or ethnic medicine for the treatment of respiratory diseases, pain, bleeding and inflammation. Rhododendron is known for its abundant metabolites, especially diterpenoids. In the past 13 years, a total of 610 chemical constituents were reported from Rhododendron plants, including 222 diterpenoids, 122 triterpenoids, 103 meroterpenoids, 71 flavonoids and 92 other constituents (lignans, phenylpropanoids, phenolic acids, monoterpenoids, sesquiterpenoids, coumarins, steroids, fatty acids). Moreover, the bioactivities of various extracts and isolates, both in vitro and in vivo, were also investigated. Our review summarized the research progress of Rhododendron regarding traditional uses, phytochemistry and pharmacology in the past 13 years (2010 to December 2022), which will provide new insight for prompting further research on Rhododendron application and drug development.

Onygenaleosides A-F, 6/5 Bicyclic Ring Skeleton Triterpene Glycosides with Insecticidal Activity from Onygenales sp. YX1425

Six new squalene derived polyether glycosides, onygenaleosides A-F (1-6), that possess a 6/5 bicyclic fused ring skeleton were isolated from the cultures of Onygenales sp. YX1425, along with two known analogues (7 and 8). The planar structures of the new compounds were elucidated based on analysis of NMR and MS spectroscopy data, and the absolute configuration of 1 was determined by the advanced Mosher method and quantum chemical calculations. Compound 2 was active against Spodoptera frugiperda with an LC50 value of 193.4 ± 1.1 μg/mL.

Esterification with a Long-Chain Fatty Acid Elevates the Exposure Toxicity of Tigliane Diterpenoids from Euphorbia fischeriana Roots against Nematodes

In this study, two tigliane diterpenoids, 12-deoxyphorbol-13-hexadecanoate and 12-deoxyphorbol-13-acetate (prostratin), were identified from the methanol extract of the roots of Euphorbia fischeriana and were found to have the ability to significantly reduce the survival of Caenorhabditis elegans. It was determined that exposure to these two compounds had toxic effects on the growth, reproduction, locomotion behavior, and accumulation of lipids and lipofuscin of the nematodes. Moreover, the transcription levels of the genes associated with lipid accumulation, apoptosis, insulin, and nuclear hormone synthesis in C. elegans were significantly influenced. Interestingly, 12-deoxyphorbol-13-hexadecanoate produced exposure toxicity at lower concentrations than that of prostratin. Pearson correlation analysis indicates that the elevated exposure toxicity of 12-deoxyphorbol-13-hexadecanoate may be the result of differing transcription levels, which result from the differential expression of fat-6, egl-38, and cep-1. These results reveal that esterification with a long-chain fatty acid elevates the exposure toxicity of this tigliane diterpenoid, thus providing a basis for the application of tigliane diterpenoids in plant-derived nematicides.

Antiproliferative and cell cycle arrest potentials of 3-O-acetyl-11-keto-β-boswellic acid against MCF-7 cells in vitro

INTRODUCTION

Cancer is a major issue in medical science with increasing death cases every year worldwide. Therefore, searching for alternatives and nonorthodox methods of treatments with high efficiency, selectivity and less toxicity is the main goal in fighting cancer. Acetyl-11-keto-β-boswellic acid (AKBA), is a derivative pentacyclic triterpenoid that exhibited various biological activities with potential anti-tumoral agents. In this research, AKBA was utilized to examine the potential cytotoxic activity against MCF-7 cells in vitro and monitor the cellular and morphological changes with a prospective impact on apoptosis induction.

METHODS

The cytotoxic activity of AKBA was measured by 3(4,5dimethylthiazole- 2-yl)-2,5 diphyneltetrazolium bromide (MTT) assay. A dose-dependent inhibition in MCF-7 cell viability was detected. The clonogenicity of MCF-7 cells was significantly suppressed by AKBA increment in comparison with untreated cells.

RESULT

Morphologically, exposure of MCF-7 cells to high AKBA concentrations caused changes in cell nuclear morphology which was indicated by increasing in nuclear size and cell permeability intensity. The mitochondrial membrane potential (ΔΨm) was reduced by increasing AKBA concentration with a significant release of cytochrome c. Acridine orange/ethidium bromide dual staining experiment confirmed that MCF-7 cells treated with AKBA (IC50 concentration) displayed a late stage of apoptosis indicated by intense and bright reddish colour.

CONCLUSION

A significant increase in reactive oxygen species formation was observed. Caspase 8 and caspase 9 activities were estimated and AKBA activated the production of caspase 8 and caspase 9 in a dose-dependent pattern. Finally, the cell phase distribution analysis was conducted, and flow cytometric analysis showed that AKBA at 200 μg mL-1 significantly arrest MCF-7 cells at the G1 phase and triggered apoptosis.

Total Synthesis and Structure Revision of (+)-Lancilactone C

Lancilactone C is a tricyclic triterpenoid that inhibits human immunodeficiency virus (HIV) replication in H9 lymphocytes with no cytotoxicity. Its tricyclic skeleton comprises trans-dimethylbicyclo[4.3.0]nonane and 7-isopropylenecyclohepta-1,3,5-triene. The latter unique structure, in which all carbon atoms are sp² hybridized, is not found in other triterpenoids and needs to be verified synthetically. Herein, we have accomplished the first total synthesis of lancilactone C (proposed structure) by developing a new domino [4 + 3] cycloaddition reaction involving oxidation, Diels-Alder reaction, elimination, and electrocyclization. We have also revised the structure based on the total synthesis of lancilactone C according to its plausible biosynthetic pathway.

Triterpenoids from Uncaria macrophylla as ferroptosis inhibitors

Seven undescribed triterpenoids were obtained from the ethanol extract of the dried stems of Uncaria macrophylla Wall. (Rubiaceae).All of the isolates were urs-28-oic acid or olean-28-oic acid skeletons, including three triterpenoids with rare 3β,23-(1R-4-hydroxy-butyl-1,1-dioxy) or 23-(2R-tetrahydrofuran-2-oxy) substituents. Five triterpenoids showed promising inhibitory activity against erastin-induced ferroptosis in PC12 cells, while 3β,6α,23-trihydroxy-olean-12-en-28-oic acid was the most significant inhibitor to resist ferroptosis by activating the Nrf2/SLC7A11/GPx4 axis with an EC₅₀ value of 4.2 ± 0.7 μM.

Naturally occurring dimeric triterpenoids: Occurrence, chemistry and bioactivities

The triterpenes represent one of the most reported subclasses of specialized metabolites from the plant kingdom. They play a key role in the protection of plants and their metabolism in addition to displaying a high structural diversity and large scale of biological activities. The scaffold can undergo several reactions like oxidation or substitution at different positions of the skeleton leading to the formation of several types of compounds. More specifically, triterpene dimer is a small group of compounds found in nature (from plants precisely). Until 2021, the chemical and pharmacological works reported in the literature indicated the identification of 90 natural dimeric triterpenes and 11 synthetic derivatives from 19 plants species and very few of them have been biologically evaluated for their antibacterial, antioxidant, antiproliferative or molluscicide activities. This review aims to compile the literature on the occurrence, chemistry and biological activities of the triterpenoid dimers. To attend this goal, a literature survey has been done in a number of online libraries including Scifinder, PubMed, Web of Science and Google Scholar using keywords terpene, triterpene, dimer, celastroloid without language restriction. This paper provides the easiest access to the information on triterpene dimers for readers and researchers in view to enhancing the continuity of research works on this topic.

CRISPR-Cas system in microbial hosts for terpenoid production

Terpenoids represent the largest group of secondary metabolites with variable structures and functions. Terpenoids are well known for their beneficial application in human life, such as pharmaceutical products, vitamins, hormones, anticancer drugs, cosmetics, flavors and fragrances, foods, agriculture, and biofuels. Recently, engineering microbial cells have been provided with a sustainable approach to produce terpenoids with high yields. Noticeably, the clustered regularly interspaced short palindromic repeats (CRISPR)-associated (Cas) system has emerged as one of the most efficient genome-editing technologies to engineer microorganisms for improving terpenoid production. In this review, we summarize the application of the CRISPR-Cas system for the production of terpenoids in microbial hosts such as Escherichia coli, Saccharomyces cerevisiae, Corynebacterium glutamicum, and Pseudomonas putida. CRISPR-Cas9 deactivated Cas9 (dCas9)-based CRISPR (CRISPRi), and the dCas9-based activator (CRISPRa) have been used in either individual or combinatorial systems to control the metabolic flux for enhancing the production of terpenoids. Finally, the prospects of using the CRISPR-Cas system in terpenoid production are also discussed.

A post processing strategy to score and rank the annotation confidence of saponins in natural products by integrating MS2 spectral similarity and fragment interpretation

Tandem mass spectrometry-spectra-based annotation in natural products challenges a lot because of ambiguous structural characterization. It still lacks an efficiency method to score and rank the annotation confidence. Herein, we develop a novel approach to rank the annotation confidences of saponins. Annotations were accomplished according to fragmentation patterns. The corresponding diagnostic fragments and their abundances were recorded. Average abundances were taken as a reference spectrum, and the cosine similarity score (CSS) was calculated to measure how well the spectral matched. According to CSS values, statistic description for confidence levels can be effectively provided. Next, the fragment interpretation score (FIS) was proposed to investigate the deviators' characteristic fragmentation. FIS offset the effect from the deviators' unique fragments. Suspicious annotations involving low CSS and high FIS, may derived from the MS² spectral background interferences or co-elution. Annotations with low CSS and FIS rank as low confidences, as these annotations need more attention. Using this method, novel saccharide sequences, specific fragmentation preferences, undistinguished precursors, even new structures can also be well traced. By proposed new scoring system, confidence evaluations can be ranked, resulting in significantly enhanced annotation reliability.

Substituted dienes prepared from betulinic acid - Synthesis, cytotoxicity, mechanism of action, and pharmacological parameters

A set of new substituted dienes were synthesized from betulinic acid by its oxidation to 30-oxobetulinic acid followed by the Wittig reaction. Cytotoxicity of all compounds was tested in vitro in eight cancer cell lines and two noncancer fibroblasts. Almost all dienes were more cytotoxic than betulinic acid. Compounds 4.22, 4.30, 4.33, 4.39 had IC₅₀ below 5 μmol/L; 4.22 and 4.39 were selected for studies of the mechanism of action. Cell cycle analysis revealed an increase in the number of apoptotic cells at 5 × IC₅₀ concentration, where activation of irreversible changes leading to cell death can be expected. Both 4.22 and 4.39 led to the accumulation of cells in the G0/G1 phase with partial inhibition of DNA/RNA synthesis at 1 × IC₅₀ and almost complete inhibition at 5 × IC₅₀. Interestingly, compound 4.39 at 5 × IC₅₀ caused the accumulation of cells in the S phase. Higher concentrations of tested drugs probably inhibit more off-targets than lower concentrations. Mechanisms disrupting cellular metabolism can induce the accumulation of cells in the S phase. Both compounds 4.22 and 4.39 trigger selective apoptosis in cancer cells via intrinsic pathway, which we have demonstrated by changes in the expression of the crucial apoptosis-related protein. Pharmacological parameters of derivative 4.22 were superior to 4.39, therefore 4.22 was the finally selected candidate for the development of anticancer drug.

Quassinoids: Phytochemistry and antitumor prospect

Quassinoids, originating from the oxidative degradation of tetracyclic tirucallane triterpene, are a diverse class of secondary metabolites identifying from nature mostly in Simaroubaceae family. The crucial pharmacological activities and structural complexity of quassinoids have long fascinated scientists due to their medicinal uses, infamous toxicity, and unique biosynthesis. In the past few decades, 482 quassinoids, assigned to 6 skeletons, have been isolated and identified from plants. The names, classes, molecular formula, and plant sources of these secondary metabolites are collated here. This review will be a detailed update of the naturally occurring quassinoids reported from the plant kingdom, providing an in-depth discussion of their diversity, antitumor activities, structure-activity relationship.

Triterpenes induced by young apple fruits in response to herbivore attack

Apples Malus domestica, known as a rich source of triterpene acids, induced more variety and quantity of triterpene acids in response to herbivory or mechanical damage. There were 3 major induced compounds: pomaceic acid and euscaphic acid, both of which are known apple triterpene acids, and 2α,19α-dihydroxy-3-oxours-12-en-28-oic acid (named eriobotoric acid), which was first identified in apples. In this study, the 3 compounds' induction curves after damage, varietal differences in induction amounts, and physiological roles against pest insects were further investigated. Eriobotoric acid showed clear antifeedant activity against lepidopteran insect Spodoptera litura but not against apple pests.

Structural Elucidation of Three 9,11-Seco Tetracyclic Triterpenoids Enables the Structural Revision of Euphorol J

Compounds 1-3, the rare examples of 9,11-seco euphane or lanostane triterpenoids featuring an enol-hemiacetal functionality, were isolated from Euphorbia stracheyi. Their structures were elucidated by a combination of spectroscopic, computational, chemical, and single-crystal X-ray diffraction means, which enables the structure of previously published euphorol J to be revised as 1. 1-3 showed significant cytotoxicities on the breast cancer cell line MDA-MB-468 with IC₅₀ values in the range of 2.9-3.9 μM.

α-Glucosidase inhibitory triterpenoids from Euonymus fortunei

α-Glucosidase plays an important role in catalyzing the hydrolytic cleavage of disaccharides into monosaccharides. In this study, a phytochemical investigation of the potential α-glucosidase inhibitory fraction from the aerial parts of Euonymus fortunei led to the isolation and identification of two new tetracyclic triterpenoids, fortunenones A and B (1-2), together with 11 known triterpenoids (3-13). Fortunenones A and B are rare C₃₂ triterpenoids possessing a 24,24-dimethyl group. The partial isolated compounds were evaluated their effects on α-glucosidase, of which echinochlorin D (5), lupenone (7), wilforlide B (12), and wilforlide A (13) exhibited remarkable inhibitory effects with the half inhibitory concentration ranged from 207.2 × 10^-6 M to 388.3 × 10^-6 M compared with the positive control, acarbose. An enzyme kinetics analysis by Lineweaver-Burk plots revealed that the inhibition types of the four active compounds were all mixed inhibition. Molecular docking further revealed that hydrophobic interactions and hydrogen bonds play an important role in the inhibition of α-glucosidase activity. Our results demonstrate the potential of E. fortunei extract and its constituents to inhibit α-glucosidase.

Biocatalysis in the Chemistry of Lupane Triterpenoids

Pentacyclic triterpenes are important representatives of natural products that exhibit a wide variety of biological activities. These activities suggest that these compounds may represent potential medicines for the treatment of cancer and viral, bacterial, or protozoal infections. Naturally occurring triterpenes usually have several drawbacks, such as limited activity and insufficient solubility and bioavailability; therefore, they need to be modified to obtain compounds suitable for drug development. Modifications can be achieved either by methods of standard organic synthesis or with the use of biocatalysts, such as enzymes or enzyme systems within living organisms. In most cases, these modifications result in the preparation of esters, amides, saponins, or sugar conjugates. Notably, while standard organic synthesis has been heavily used and developed, the use of the latter methodology has been rather limited, but it appears that biocatalysis has recently sparked considerably wider interest within the scientific community. Among triterpenes, derivatives of lupane play important roles. This review therefore summarizes the natural occurrence and sources of lupane triterpenoids, their biosynthesis, and semisynthetic methods that may be used for the production of betulinic acid from abundant and inexpensive betulin. Most importantly, this article compares chemical transformations of lupane triterpenoids with analogous reactions performed by biocatalysts and highlights a large space for the future development of biocatalysis in this field. The results of this study may serve as a summary of the current state of research and demonstrate the potential of the method in future applications.

Optimization, Validation and Application of HPLC-PDA Methods for Quantification of Triterpenoids in Vaccinium vitis-idaea L

Triterpenoids have regained much attention as promising multi-targeting bioactive agents of natural origin in the treatment of numerous disorders. Due to the high potential for phytopharmaceutical development, accurate qualitative and quantitative analysis of triterpenoids for screening and quality control is required. Vaccinium vitis-idaea L. (lingonberry) raw materials have aroused interest as a rich source of triterpenoids. However, currently, no validated, rapid, and easy-to-perform quantification method is available for the routine control of these compounds in lingonberries. This research aimed at developing and validating HPLC-PDA methods for the determination and screening of triterpenoids in extracts of lingonberry leaves, fruits, and flowers. The developed methods were deemed satisfactory by validation, which revealed acceptable analytical specificity, linearity (r2 > 0.9999), precision (RSD < 2%), trueness (94.70-105.81%), and sensitivity (LOD: 0.08-0.65 µg/mL). The real sample analysis demonstrated established methods applicability for quantification of 13 triterpenoids in lingonberries and emphasized differences between raw materials. Lingonberry fruits were distinguished by the richness of ursolic acid; lingonberry flowers by similar profile to fruits, but low content of neutral triterpenoids; whereas lingonberry leaves by the particularly high level of α-amyrin. Thus, the proposed methods proved to be reliable and applicable for quantification and routine analysis of triterpenoids in lingonberry samples.

Therapeutic Potential of RTA 404 in Human Brain Malignant Glioma Cell Lines via Cell Cycle Arrest via p21/AKT Signaling

Background

Glioblastoma multiforme (GBM) is the most common malignant brain tumor in the world. Despite advances in surgical resection, radiotherapy, and chemotherapy, GBM continues to have a poor overall survival. CDDO (2-cyano-3,12-dioxoolean-1,9-dien-28-oic acid), a synthetic triterpenoid, is an Nrf2 activator used to inhibit proliferation and induce differentiation and apoptosis in various cancer cells. One new trifluoroethylamide derivative of CDDO, RTA 404, has been found to have increased ability to cross the blood-brain barrier. However, it is not clear what effect it may have on tumorigenesis in GBM.

Methods

This in vitro study evaluated the effects of RTA 404 on GBM cells. To do this, we treated GBM840 and U87 MG cell lines with RTA 404 and assessed apoptosis, cell cycle, cell locomotion, and senescence. DNA content and induction of apoptosis were analyzed by flow cytometry and protein expression by Western blot analysis.

Results

RTA 404 significantly inhibited the proliferation of tumor cells at concentrations higher than 100 nM (p < 0.05) and reduced their locomotion ability. In addition, treatment with RTA 404 led to an accumulation of RTA 404-treated G₂/M phase cells and apoptosis. An analysis of the p21/AKT expression suggested that RTA 404 may not only help prevent brain cancer but it may also exert antitumor activities in established GBM cells.

Conclusion

RTA404 can inhibit proliferation, cell locomotion, cell cycle progression, and induce apoptosis in GBM cells in vitro, possibly through its inhibition of N-cadherin and E-cadherin expression via its inhibition of the AKT pathway.

Novel pentacyclic triterpenes exhibiting strong neuroprotective activity in SH-SY5Y cells in salsolinol- and glutamate-induced neurodegeneration models

Novel triterpene derivatives were prepared and evaluated in salsolinol (SAL)- and glutamate (Glu)-induced models of neurodegeneration in neuron-like SH-SY5Y cells. Among the tested compounds, betulin triazole 4 bearing a tetraacetyl-β-d-glucose substituent showed a highly potent neuroprotective effect. Further studies revealed that removal of tetraacetyl-β-d-glucose part (free triazole derivative 10) resulted in strong neuroprotection in the SAL model at 1 μM, but this derivative suffered from cytotoxicity at higher concentrations. Both compounds modulated oxidative stress and caspase-3,7 activity, but 10 showed a superior effect comparable to the Ac-DEVD-CHO inhibitor. Interestingly, while both 4 and 10 outperformed the positive controls in blocking mitochondrial permeability transition pore opening, only 4 demonstrated potent restoration of the mitochondrial membrane potential (MMP) in the model. Derivatives 4 and 10 also showed neuroprotection in the Glu model, with 10 exhibiting the strongest oxidative stress reducing effect among the tested compounds, while the neuroprotective activity of 4 was probably due recovery of the MMP.

Bismuth(III)-catalyzed bis-cyclization of propargylic diol-esters: a unified approach for the synthesis of [5,5]- and [6,5]-oxaspirolactones

Herein we disclose an unprecedented intramolecular cascade strategy for the construction of α,β-unsaturated [5,5]- and [6,5]-oxaspirolactones that capitalizes on the π-electrophilic Lewis acid-catalyzed 5-exo-dig or 6-exo-dig mode of cyclization of propargylic diol esters, followed by dehydration and spirolactonization steps. Moreover, semi-protected substrates also delivered the respective oxaspirolactones with the same ease and in appreciable yields under optimal reaction conditions.

Food Bioactive Compounds and Emerging Techniques for Their Extraction: Polyphenols as a Case Study

Experimental studies have provided convincing evidence that food bioactive compounds (FBCs) have a positive biological impact on human health, exerting protective effects against non-communicable diseases (NCD) including cancer and cardiovascular (CVDs), metabolic, and neurodegenerative disorders (NDDs). These benefits have been associated with the presence of secondary metabolites, namely polyphenols, glucosinolates, carotenoids, terpenoids, alkaloids, saponins, vitamins, and fibres, among others, derived from their antioxidant, antiatherogenic, anti-inflammatory, antimicrobial, antithrombotic, cardioprotective, and vasodilator properties. Polyphenols as one of the most abundant classes of bioactive compounds present in plant-based foods emerge as a promising approach for the development of efficacious preventive agents against NCDs with reduced side effects. The aim of this review is to present comprehensive and deep insights into the potential of polyphenols, from their chemical structure classification and biosynthesis to preventive effects on NCDs, namely cancer, CVDs, and NDDS. The challenge of polyphenols bioavailability and bioaccessibility will be explored in addition to useful industrial and environmental applications. Advanced and emerging extraction techniques will be highlighted and the high-resolution analytical techniques used for FBCs characterization, identification, and quantification will be considered.

Bioactive Natural Small Molecule-Tuned Coassembly of Photosensitive Drugs for Highly Efficient Synergistic and Enhanced Type I Photochemotherapy

Self-assembling natural small molecules (NSMs) with favorable anticancer activity are of increasing interest as novel drug delivery platforms without structural modification for biomedical applications. However, a lack of knowledge and practicability of NSMs as drug carriers limited their current biomedical application. Here, via a green and facile supramolecular coassembly strategy, we report and develop a series of carrier-free terpenoid natural small molecule-mediated coassembled photosensitive drugs for enhanced and synergistic chemo/photodynamic therapy. After screening 17 terpenoid NSMs, we identified 11 compounds that could form coassembled NSMs-Ce6 NPs with regulatable drug sizes. Analysis of the representative betulonic acid (BC)-mediated nano-coassemblies (BC-Ce6 NPs) reveals the high efficiency of the coassembly strategy and highlights the tremendous potential of NSMs as novel drug delivery platforms. Through molecular dynamics simulation and theoretical calculations, we elucidate the mystery of the coassembly process, indicating that the linear coplanar arrangement of BC dimeric units is primarily responsible for the formation of rod-like or spherical morphology. Meanwhile, we demonstrated that the reduced energy gap between the singlet and triplet excited states (ΔE_ST) facilitates efficient reactive oxygen species generation by promoting ·OH generation via a type I photoreaction mechanism. The assembled nanodrugs exhibit multiple favorable therapeutic features, ensuring a remarkably enhanced, synergistic, and secure combinatorial anticancer efficacy of 93.6% with highly efficient tumor ablation. This work not only expands the possibility of natural biodegradable materials for wide biological applications but also provides a new perspective for the construction of NSM-mediated nano-coassemblies for precision therapy.

Structure reassignment of two triterpenes with CASE algorithms and DFT chemical shift predictions

Two triterpenes (14S,17S,20S,24R)-25-hydroxy-14,17-cyclo-20,24-epoxy-malabarican-3-one (CEM, 1a) and (14S,17S,20S,24R)-20,24,25-trihydroxy-14,17-cyclomalabarican-3-one (CM, 2a) with a cyclobutane ring were reported, which have the same NMR data as ocotillone (1b) and gardaubryone C (2b), respectively. An incorrect structure might be reported. Therefore, the structure reanalysis of these triterpenes was achieved by CASE algorithm and DFT chemical shift predictions, and the results showed that the structures of CEM and CM might be incorrect. To further verify the structure of compound 1, the HMBC, ¹H-¹H COSY and HSQC-TOCSY spectra were employed. Herein, we revised the structure of CEM and CM, and our study also showed that CASE algorithm and DFT chemical shift predictions can hold the post of effective structure reassignment method.

Design, Synthesis, and Cytotoxic Evaluation of Novel Lupane Triterpenoid Derived Hydroxamates

A series of new hydroxamate derivatives of lupane triterpenoids has been designed and successfully synthesized. The synthesized compounds were evaluated for their in vitro antitumor activity using the 3-[4,5-dimethylthiazol-2-yl]−2,5-diphenyltetrazolium bromide-based assay against the human cancer cell lines KB and HepG2. Most of these derivatives possess at least moderate cytotoxic activity and the hydroxamate derivative compounds 3c, 3e, 7a, and 15b could be lead compounds for further optimization to develop novel anticancer agents.

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.

The Chemical Structure and Bioactivity of Cycloartane-type Compounds

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For decades now, compounds in the cycloartane-type series have been shown to have versatile pharmacological activities. However, no extensive review has been written to summarize these health-beneficial activities. Therefore, the purpose of this paper is to systematically highlight the biological activities of these compounds, including their antitumor and anti-osteoporosis effects, their effects on receptors, cytokine release, and chronic renal failure, as well as their tyrosinase inhibitory, anticomplement, anti-parasite, anti-HIV, and antituberculosis activities. In this review, we have summarized the structures of over 200 compounds based on their characteristics and described their structureactivity relationships (SARs), and potential mechanisms of action.

Design and synthesis of pentacyclic triterpene conjugates and their use in medicinal research

Triterpenoids are natural products from plants and many other organisms that have various biological activities, such as antitumor, antiviral, antimicrobial, and protective activities. This review covers the synthesis and biological evaluation of pentacyclic triterpene (PT) conjugates with other molecules that have been found to increase the IC₅₀ or improve the pharmacological profile of the parent PT. Some of these molecules are designed to target specific proteins or cellular organelles, which has resulted in highly selective lead structures for drug development. Other PT conjugates are useful for investigating their mechanism of action. This concept has been very successful: 1) Many compounds, especially mitochondria-targeting PT conjugates, have reached a selective cytotoxicity at low nanomolar concentrations in cancer cells. 2) A number of PT conjugates have had high activity against HIV or the influenza virus. 3) Fluorescent PT conjugates have been able to visualize the PT in living cells, which has allowed quantification of the uptake and distribution of the PT within the cell. 4) Biotinylated PT conjugates have been used to identify target proteins, which may help to show their mechanism of action. 5) A large number of PT conjugates with polyethylene glycol (PEG), polyamines, etc. form nanometer-sized micelles that have a much better pharmacological profile than the PT alone. In summary, the connection of a PT to an appropriate modifying molecule has resulted in extremely useful semisynthetic compounds with a high potential to treat cancer or viral infections or compounds that are useful for the study of the mechanism of action of PTs at the molecular level.

Computational and Synthetic Investigation of Cationic Rearrangement in the Putative Biosynthesis of Justicane Triterpenoids

A biomimetic cationic structural rearrangement of the oleanolic acid framework is reported for the gram-scale synthesis and structural reassignment of justicioside E aglycone. The mechanism of the putative biosynthetic rearrangement is investigated with kinetic, computational, and synthetic approaches. The precursor to rearrangement was accessed through two strategic advancements: (1) synthesis of a 1,3-diketone via oxidation of a β-silyl enone, and (2) diastereoselective 1,3-diketone reduction to form a syn-1,3-diol using SmI2 with PhSH as a key additive.