Structural modifications of 2,3-indolobetulinic acid: Design and synthesis of highly potent α-glucosidase inhibitors

Structural modification of tanshinone IIA and their α-glucosidase inhibitory activity

α-Glucosidase is one of the therapeutic approaches for treating type 2 diabetes mellitus. Almost 95 % of diabetes patients worldwide have been diagnosed with type 2 diabetes, resulting in 1.5 million fatalities each year. Newly synthesized oxazole-based tanshinone IIA derivatives (1a-n) were designed and evaluated for their inhibitory activity against α-glucosidase enzyme. Eight compounds (1a-d, 1f-g, 1j, and 1m) demonstrated excellent inhibition with IC50 values ranging from 0.73 ± 0.11 to 9.46 ± 0.57 μM as compared to tanshinone IIA (IC50 = 11.39 ± 0.77 μM) and standard acarbose (IC50 = 100.00 ± 0.95 μM). Among this series, 1j bearing two hydroxyls group over the phenyl ring was identified as the most potent α-glucosidase inhibitor with IC50 value of 0.73 ± 0.11 μM. Molecular docking simulations were done for the most active compound to identify important binding modes responsible for inhibition activity of α-glucosidase. In addition, the kinetic study was also performed to understand the mode of inhibition.

Synthesis, modification and biological activity of 2,3-indoles of Glycyrrhetinic acid

The synthesis of 2,3-indoles of Glycyrrhetinic acid (GLA) and its methyl ester was carried out by the Fischer reaction. Reductive transformations of GLA methyl ester 2,3-indole 3a were carried out to obtain 11-deoxo- and 9,12-diene analogs. N-methylation of 2,3-indole 3a gave N-methyl-indole-11-oxo-18β-olean-12-en-30-oic acid. The antiulcer and anti-inflammatory activity of 2,3-indole 3a was studied in rats and mice. It was found, compound 3a exhibied a pronounced antiulcer activity in the indomethacin model of ulcers in rats and anti-inflammatory activity in the carrageenan model of acute edoema in mice, at a dose of 50 mg/kg. This is the first report of anti-ulcer and anti-inflammatory activities of 2,3-indolo-GLA derivatives.

Antiviral opportunities of Mannich bases derived from triterpenic N-propargylated indoles

Oleanolic and glycyrrhetic acids alkyne derivatives were synthesized as a result of propargylation of the indole NH-group condensed with the triterpene A-ring, the following aminomethylation led to a series of Mannich bases. The synthesized compounds were tested for their potential inhibition of influenza A/PuertoRico/8/34 (H1N1) virus in Madin-Darby canine kidney (MDCK) cell culture and SARS-CoV-2 pseudovirus in baby hamster kidney-21-human angiotensin-converting enzyme 2 (BHK-21-hACE2) cells. Mannich bases of oleanolic and glycyrrhetic acids N-propargylated indoles 7, 8, and 12 were the most efficacious against influenza virus A with IC50 7-10 μM together with a low toxicity (CC50  > 145 μM) and high selectivity index SI value 20. Indolo-oleanolic acid morpholine amide Mannich base holding N-methylpiperazine moiety 9 showed anti-SARS-CoV-2 pseudovirus activity with EC50 value of 14.8 μM. Molecular docking and dynamics modeling investigated the binding mode of the compounds 7 and 12 into the binding pocket of influenza A virus M2 protein and compound 9 into the RBD domain of SARS-CoV-2 spike glycoprotein.

Enhanced Cytotoxicity and Antimelanoma Activity of Novel Semisynthetic Derivatives of Betulinic Acid with Indole Conjugation

The prevalence and severity of skin cancer, specifically malignant melanoma, among Caucasians remains a significant concern. Natural compounds from plants have long been explored as potential anticancer agents. Betulinic acid (BI) has shown promise in its therapeutic properties, including its anticancer effects. However, its limited bioavailability has hindered its medicinal applications. To address this issue, two recently synthesized semisynthetic derivatives, N-(2,3-indolo-betulinoyl)diglycylglycine (BA1) and N-(2,3-indolo-betulinoyl)glycylglycine (BA2), were compared with previously reported compounds N-(2,3-indolo-betulinoyl)glycine (BA3), 2,3-indolo-betulinic acid (BA4), and BI. These compounds were evaluated for their effects on murine melanoma cells (B164A5) using various in vitro assays. The introduction of an indole framework at the C2 position of BI resulted in an increased cytotoxicity. Furthermore, the cytotoxicity of compound BA4 was enhanced by conjugating its carboxylic group with an amino acid residue. BA2 and BA3, with glycine and glycylglycine residues at C28, exhibited approximately 2.20-fold higher inhibitory activity compared to BA4. The safety assessment of the compounds on human keratinocytes (HaCaT) has revealed that concentrations up to 10 µM slightly reduced cell viability, while concentrations of 75 µM resulted in lower cell viability rates. LDH leakage assays confirmed cell membrane damage in B164A5 cells when exposed to the tested compounds. BA2 and BA3 exhibited the highest LDH release, indicating their strong cytotoxicity. The NR assay revealed dose-dependent lysosome disruption for BI and 2,3-indolo-betulinic acid derivatives, with BA1, BA2, and BA3 showing the most cytotoxic effects. Scratch assays demonstrated concentration-dependent inhibition of cell migration, with BA2 and BA3 being the most effective. Hoechst 3342 staining revealed that BA2 induced apoptosis, while BA3 induced necrosis at lower concentrations, confirming their anti-melanoma properties. In conclusion, the semisynthetic derivatives of BI, particularly BA2 and BA3, show promise as potential candidates for further research in developing effective anti-cancer therapies.

Research status of indole-modified natural products

Indole is a heterocyclic compound formed by the fusion of a benzene ring and pyrrole ring, which has rich biological activity. Many indole-containing compounds have been sold on the market due to their excellent pharmacological activity. For example, vincristine and reserpine have been widely used in clinical practice. The diverse structures and biological activities of natural products provide abundant resources for the development of new drugs. Therefore, this review classifies natural products by structure, and summarizes the research progress of indole-containing natural product derivatives, their biological activities, structure-activity relationship and research mechanism which has been studied in the past 13 years, so as to provide a basis for the development of new drug development.

Research progress of indole-fused derivatives as allosteric modulators: Opportunities for drug development

Allosteric modulation is a direct and effective method for regulating the function of biological macromolecules, which play vital roles in various cellular activities. Unlike orthosteric modulators, allosteric modulators bind to sites distant from the protein's orthosteric/active site and can have specific effects on the protein's function or activity without competing with endogenous ligands. Compared to traditional orthosteric modulators, allosteric modulators offer several advantages, including reduced side effects, greater specificity, and lower toxicity, making them a promising strategy for developing novel drugs. Indole-fused architectures are widely distributed in natural products and bioactive drug leads, displaying diverse biological activities that attract the interest of both chemists and biologists in drug discovery. Currently, an increasing number of indole-fused compounds have exhibited potent activities in allosteric modulation. In this review, we provide a brief summary of examples of allosteric modulators based on the indole-fused complex architecture, highlighting the strategies for drug design/discovery and the structure-activity relationships of allosteric modulators from the perspective of medicinal chemistry.

Comparison of In Vitro Antimelanoma and Antimicrobial Activity of 2,3-Indolo-betulinic Acid and Its Glycine Conjugates

Malignant melanoma is one of the most pressing problems in the developing world. New therapeutic agents that might be effective in treating malignancies that have developed resistance to conventional medications are urgently required. Semisynthesis is an essential method for improving the biological activity and the therapeutic efficacy of natural product precursors. Semisynthetic derivatives of natural compounds are valuable sources of new drug candidates with a variety of pharmacological actions, including anticancer ones. Two novel semisynthetic derivatives of betulinic acid-N-(2,3-indolo-betulinoyl)diglycylglycine (BA1) and N-(2,3-indolo-betulinoyl)glycylglycine (BA2)-were designed and their antiproliferative, cytotoxic, and anti-migratory activity against A375 human melanoma cells was determined in comparison with known N-(2,3-indolo-betulinoyl)glycine (BA3), 2,3-indolo-betulinic acid (BA4) and naturally occurring betulinic acid (BI). A dose-dependent antiproliferative effect with IC₅₀ values that ranged from 5.7 to 19.6 µM was observed in the series of all five compounds including betulinic acid. The novel compounds BA1 (IC₅₀ = 5.7 µM) and BA2 (IC₅₀ = 10.0 µM) were three times and two times more active than the parent cyclic structure B4 and natural BI. Additionally, compounds BA2, BA3, and BA4 possess antibacterial activity against Streptococcus pyogenes ATCC 19615 and Staphylococcus aureus ATCC 25923 with MIC values in the range of 13-16 µg/mL and 26-32 µg/mL, respectively. On the other hand, antifungal activity toward Candida albicans ATCC 10231 and Candida parapsilosis ATCC 22019 was found for compound BA3 with MIC 29 µg/mL. This is the first report of antibacterial and antifungal activity of 2,3-indolo-betulinic acid derivatives and also the first extended report on their anti-melanoma activity, which among others includes data on anti-migratory activity and shows the significance of amino acid side chain on the observed activity. The obtained data justify further research on the anti-melanoma and antimicrobial activity of 2,3-indolo-betulinic acid derivatives.

Root-Extracted lignanamides from Limonium gmelinii (Willd.) Kuntze with a potential PTP1B inhibitory activity by regulating PI3K/AKT signaling pathway

The phytochemical study of Limonium gmelinii roots resulted in the isolation of five lignanamides (1-5). Among them, limoniumins J, K, and M (1, 2, and 4) are undescribed compounds, limoniumin L (3) is a new naturally occurring lignanamide, and limoniumin B (5) is a known compound which showed PTP1B inhibition activity with an IC₅₀ value of 5.05 ± 2.44 μM in our previous work. Spectroscopic data analysis, including 1D and 2D NMR and HRESIMS experiments, established the chemical structures of limoniumins J - M (1-4). Compounds 1-4 showed PTP1B inhibition activity, among which compound 3 showed the most potent PTP1B inhibition with an IC₅₀ value of 2.07 ± 0.05 μM. Compounds 3 and 5 could significantly increase cellular glucose consumption and glucose uptake in L6 muscle cells and could synergize with insulin to promote glucose consumption and glucose uptake in a concentration-dependent manner. The treatment of compound 3 also promoted glycogen synthesis in skeletal muscle cells. Western blot analysis demonstrated that the good hypoglycemic effect of compounds 3 and 5 was achieved by activating PI3K/AKT signaling pathway to promote glucose consumption, glucose uptake, and glycogen synthesis. Furthermore, studies on molecular docking revealed the potent interactions between these bioactive substances and the PTP1B protein.

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.

Binding Interaction of Betulinic Acid to α-Glucosidase and Its Alleviation on Postprandial Hyperglycemia

Inhibiting the intestinal α-glucosidase can effectively control postprandial hyperglycemia for type 2 diabetes mellitus (T2DM) treatment. In the present study, we reported the binding interaction of betulinic acid (BA), a pentacyclic triterpene widely distributed in nature, on α-glucosidase and its alleviation on postprandial hyperglycemia. BA was verified to exhibit a strong inhibitory effect against α-glucosidase with an IC₅₀ value of 16.83 ± 1.16 μM. More importantly, it showed a synergistically inhibitory effect with acarbose. The underlying inhibitory mechanism was investigated by kinetics analysis, surface plasmon resonance (SPR) detection, molecular docking, molecular dynamics (MD) simulation and binding free energy calculation. BA showed a non-competitive inhibition on α-glucosidase. SPR revealed that it had a strong and fast affinity to α-glucosidase with an equilibrium dissociation constant (K_D) value of 5.529 × 10⁻⁵ M and a slow dissociation. Molecular docking and MD simulation revealed that BA bound to the active site of α-glucosidase mainly due to the van der Waals force and hydrogen bond, and then changed the micro-environment and secondary structure of α-glucosidase. Free energy decomposition indicated amino acid residues such as PHE155, PHE175, HIE277, PHE298, GLU302, TRY311 and ASP347 of α-glucosidase at the binding pocket had strong interactions with BA, while LYS153, ARG210, ARG310, ARG354 and ARG437 showed a negative contribution to binding affinity between BA and α-glucosidase. Significantly, oral administration of BA alleviated the postprandial blood glucose fluctuations in mice. This work may provide new insights into the utilization of BA as a functional food and natural medicine for the control of postprandial hyperglycemia.

Pentacyclic triterpene carboxylic acids derivatives integrated piperazine-amino acid complexes for α-glucosidase inhibition in vitro

Eighteen derivatives of pentacyclic triterpene carboxylic acids (Maslinic acid, Corosolic acid and Asiatic acid) have been prepared by coupling the piperazine complex of l-amino acids at the C-28 site of the parent compounds. The α-glucosidase inhibitory activities of the pristine derivatives were evaluated in vitro. The results indicated that the inhibitory activity of some compounds (15e IC₅₀ = 591 μM, 16e IC₅₀ = 423 μM) was closed to that of the reference acarbose (IC₅₀ = 347 μM) in ethanol-water system. In addition, compound 16e (IC₅₀ = 380 μM) showed superior inhibitory activity than acarbose (IC₅₀ = 493 μM) in the measurement system with DMSO as solvent. The comparison of two different solvent systems showed that the derivatives had better α-glucosidase inhibitory activity in the DMSO system than that of in ethanol-water system. Regrettably, all of the as-synthesized derivatives exhibited inferior α-glucosidase inhibitory activities than those of the parent compounds in both test solvent systems. Furthermore, the result of enzyme kinetics demonstrated that the inhibition mechanism of compound 16e was noncompetitive inhibition with the inhibition constant K_i = 552 μM.

Acankoreagenin and acankoreosides, a family of lupane triterpenoids with anti-inflammatory properties: an overview

Acankoreagenin (ACK, also known as acankoreanogenin and HLEDA) and impressic acid are two lupane-type triterpenes that can be isolated from various Acanthopanax and Schefflera species. They efficiently block activation of the NF-κB signaling pathway and the release of proinflammatory cytokines and/or the action of inflammation mediators (HMGB1, iNOS, and NO). These effects are the basis for the antiviral and anticancer activities reported with these pentacyclic compounds or their various glycoside derivatives. More than 15 acankoreosides (Ack-A to -O, and -R) and a few other mono- and bidesmosidic saponins (acantrifoside A and acangraciliside S) derive from the ACK aglycone. Compounds like Ack-A and -B are remarkable anti-inflammatory agents, inhibiting cytokine release from activated macrophages. Despite their effectiveness, ACK and impressic acid are far much less known and studied than the structurally related compounds betulinic acid and 23-hydroxybetulinic acid (anemosapogenin). The structural differences (notably the R/S stereoisomerism of the 3-hydroxyl group) and functional similarities of these compounds are discussed. The complete series of acankoreosides is presented for the first time. These natural products deserve further attention as anti-inflammatory agents, and ACK is recommended as a template for the design of new anticancer and antiviral drugs.

Synthesis and Cytotoxic Potential of 3-oxo-19β-Trifluoroacetoxy-18αH-oleane-28-oic Acid

Trifluoroacetic acid-promoted Wagner-Meerwein rearrangement of betulonic acid carboxamide led to the formation of the expected 19β,28-lactam along with a new germanicane-type 3-oxo-19β-trifluoroacetoxy-18αH-oleane-28-oic acid. The structure of this triterpenoid was confirmed by 2D NMR analyses. A primary evaluation of biological potency revealed an anticancer activity with GI50 < 5 μM against leukemia, colon cancer, breast cancer, and prostate cancer cell lines, while the parent compounds were not active.

Synthesis of messagenin and platanic acid chalcone derivatives and their biological potential

The chalcone derivatives of 20-oxo-lupanes have been synthesised and screened for some types of biological activity. Ozonolysis of lupanes afforded 20-oxo-derivatives with the following condensation using different aromatic aldehydes by Claisen‒Schmidt reaction to the target compounds. The E configuration of 19-[3-(pyridin-3-yl)-prop-2-en-1-one]-fragment was established by X-ray analysis. Screening of cytotoxic activity against NCI-60 cancer cell line panel revealed, that messagenin derivative 9 has the highest activity with GI₅₀ value ranged from 0.304 to 0.804 μM. A colorimetric SRB assay revealed for the 2,30-bis-furfurylidene derivative 11 and 30-bromo-20-oxo-29-nor-3,28-diacetoxy-betulin 16 cytotoxic activity against breast carcinoma MCF-7 and ovarian carcinoma A2780 cell lines. Compounds 11 and 13 acted also as inhibitors of the enzyme α-glucosidase (from S. saccharomyces) with IC₅₀ values of 1.76 μM and 3.3 μM thus being 97- and 52-fold more active than standard acarbose. Antiviral potency of compounds 12 and 14 against HCMV, HSV-1 and HPV is also discussed.

Precise regulation of the properties of hydrophobic carbon dots by manipulating the structural features of precursor ionic liquids

To prepare carbon dots (CDs), there are numerous protocols that use a wide variety of carbon sources, which results in properties of CDs that are unpredictable and highly variable. Therefore, the development of reliable approaches for precisely regulating the nature of CDs is urgently required. Herein, a series of organophilic/hydrophobic CDs (OCDs) were prepared under microwave agitation with ionic liquid 1-alkyl-3-methylimidazolium dicyanamide as the precursor, by varying the alkyl chain linked in the cationic imidazolium moiety. The physicochemical, optical and biological properties, and imaging performance of OCDs were exploited to elucidate the structure-activity relationship, and it was discovered that the alkyl chain plays key roles in governing the properties of OCDs. The increase in the alkyl chain length, from ethyl, butyl, hexyl, and octyl to decyl, led to a remarkable variation in the properties of the OCDs, i.e., a reduction in nitrogen doping from 40.71 to 20.75%, a decrease in binding affinity with bovine serum albumin (BSA), and an increase in cytotoxicity. The interaction of OCDs with BSA and the formation of a 'protein corona' substantially increased the biocompatibility of the OCDs. The OCDs penetrated into MCF-7 human breast cancer cells in 10 min and demonstrated bright fluorescence imaging.

Synthesis, antibacterial, and cytotoxicity evaluation of oleanolic acid-4-aminoquinoline based hybrid compounds

AIM

To prepare a class of oleanolic-based compounds.

BACKGROUND

Conventional drugs used to treat infectious diseases suffer from limitations such as drug toxicity and drug resistance. The resistance of microbes to antimicrobial agents is a significant challenge in treating microbial infections. Combining two or more drugs with different modes of action to treat microbial infections results in a delay in developing drug resistance by the microbes. However, it is challenging to select the appropriate choice of drugs for combination therapy due to the differences in stability and pharmacokinetic profile of the drugs.Therefore, developing hybrid compounds using the existing drugs is a promising approach to design effective antimicrobial agents.

OBJECTIVES

To prepare oleanolic-based hybrid compounds followed by characterization, in vitro antibacterial, and cytotoxicity evaluation.

METHODS

Oleanolic acid-4-aminoquinoline-based hybrid compounds weresynthesized via esterification and amidation. The compounds werecharacterized using FTIR, NMR, and UHPLC-HRMS. Oleanolic acid was isolated from the flower buds of Syszygium aromaticum (L.) Merr. & L.M.Perry, a specie from Kingdom Plantae, order Mytales in Myrtaceae family. Their antibacterial and cytotoxicity activity was determined against selected strains of bacteria assessed using the microdilution assay and sulforhodamine B assay against selected cancer cell lines.

RESULTS

The synthesized hybrid compounds exhibited significant antibacterial activity against the Gram-positive bacteria Enterococcus faecalis (ATCC13047), Bacillus subtilis (ATCC19659), Staphylococcus aureus as well as Gram-negative bacteria,Klebsiella oxytoca (ATCC8724), Escherischia coli (ATCC25922), and Proteus vulgaris (ATCC6380)with minimum inhibitory concentrations of 1.25 mg/mLcompared to oleanolic acid (2.5 mg/mL). Compounds 13 and 14 displayed significant cytotoxic effectsin vitro against the cancer cell lines (MCF-7 and DU 145) compared to the oleanolic acid (IC50 ˃ 200 µM).

CONCLUSION

The present study revealed that the modification of C28 of OA enhanced its biological properties.

Diarylheptanoid-chalcone hybrids with PTP1B and α-glucosidase dual inhibition from Alpinia katsumadai

The EtOH extracts of the dried seeds of Alpinia katsumadai were revealed with hypoglycemic effects on db/db mice at the concentration of 200 mg/kg. In order to clarify the antidiabetic constituents, 16 new diarylheptanoid-chalcone hybrids, katsumadainols A₁-A₁₆ (1-16), together with 13 known analogues (17-29), were isolated from A. katsumadai under the guidance of bioassay. Most of the compounds showed α-glucosidase and PTP1B dual inhibition, among which compounds 1-3, 5-7, 11-14, 21-25, and 27 showed PTP1B/TCPTP selective inhibition with IC₅₀ values ranging from 22.0 to 96.7 μM, which were 2-10 times more active than sodium orthovanadate (IC₅₀, 215.7 μM). All compounds exhibited obvious inhibition against α-glucosidase with IC₅₀ values of 2.9-29.5 μM, indicating 6-59 times more active than acarbose (IC₅₀, 170.9 μM). Study of enzyme kinetics indicated compounds 1, 3, and 12 were PTP1B and α-glucosidase mixed-type inhibitors with K_i values of 13.1, 12.9, 21.6 μM, and 4.9, 7.4, 3.4 μM, respectively.

Evaluation of Cytotoxicity and α-Glucosidase Inhibitory Activity of Amide and Polyamino-Derivatives of Lupane Triterpenoids

A series of two new and twenty earlier synthesized branched extra-amino-triterpenoids obtained by the direct coupling of betulinic/betulonic acids with polymethylenpolyamines, or by the cyanoethylation of lupane type alcohols, oximes, amines, and amides with the following reduction were evaluated for cytotoxicity toward the NCI-60 cancer cell line panel, α-glucosidase inhibitory, and antimicrobial activities. Lupane carboxamides, conjugates with diaminopropane, triethylenetetramine, and branched C3-cyanoethylated polyamine methyl betulonate showed high cytotoxic activity against most of the tested cancer cell lines with GI50 that ranged from 1.09 to 54.40 µM. Betulonic acid C28-conjugate with triethylenetetramine and C3,C28-bis-aminopropoxy-betulin were found to be potent micromolar inhibitors of yeast α-glucosidase and to simultaneously inhibit the endosomal reticulum α-glucosidase, rendering them as potentially capable to suppress tumor invasiveness and neovascularization, in addition to the direct cytotoxicity. Plausible mechanisms of cytotoxic action and underlying disrupted molecular pathways were elucidated with CellMinner pattern analysis and Gene Ontology enrichment analysis, according to which the lead compounds exert multi-target antiproliferative activity associated with oxidative stress induction and chromatin structure alteration. The betulonic acid diethylentriamine conjugate showed partial activity against methicillin-resistant S. aureus and the fungi C. neoformans. These results show that triterpenic polyamines, being analogs of steroidal squalamine and trodusquemine, are important substances for the search of new drugs with anticancer, antidiabetic, and antimicrobial activities.

Nineteen New Flavanol-Fatty Alcohol Hybrids with α-Glucosidase and PTP1B Dual Inhibition: One Unusual Type of Antidiabetic Constituent from Amomum tsao-ko

The dried fruits of Amomum tsao-ko were first revealed to have hypoglycemic effects on db/db mice at a concentration of 200 mg/kg. In order to clarify the antidiabetic constituents, 19 new flavanol-fatty alcohol hybrids, tsaokoflavanols A-S (1-19), were isolated and determined by extensive spectroscopic data and ECD calculations. Most of the compounds showed α-glucosidase and PTP1B dual inhibition, among which 1, 2, 6, 11, and 18 exhibited obvious activity against α-glucosidase with IC₅₀ values of 5.2-9.0 μM, 20-35 times stronger than that of acarbose (IC₅₀, 180.0 μM); meanwhile, 6, 10-12, and 19 were PTP1B/TCPTP-selective inhibitors with IC₅₀ values of 56.4-80.4 μM, 2-4 times stronger than that of suramin sodium (IC₅₀, 200.5 μM). Enzyme kinetics study indicated that compounds 1, 2, 6, and 11 were α-glucosidase and PTP1B mixed-type inhibitors with K_i values of 13.0, 11.7, 2.9, and 5.3 μM and 142.3, 88.9, 39.2, and 40.8 μM, respectively. Docking simulations proved the importance of hemiacetal hydroxy, the orientation of 3,4-dihydroxyphenyl, and the length of alkyl in binding with α-glucosidase and PTP1B.

A-Ring-Modified Triterpenoids and Their Spermidine–Aldimines with Strong Antibacterial Activity

Synthesis of A-ring-modified lupane, oleanane and ursane type triterpenoid conjugates with spermidine through an aldimine linkage or diethylentriamine via an amide bond is described. These derivatives were evaluated for their in vitro antimicrobial properties against human pathogens. Except for derivatives 1 and 7, all compounds have moderate to weak minimum inhibitory concentrations (MICs) against Gram-positive Staphylococcus aureus bacteria, with MICs varying from 3.125 to 200 µM. Compound 11 is efficient against Escherichia coli and Pseudomonas aeruginosa, with MICs of 25 and 50 µM, respectively, while all other derivatives do not possess important antimicrobial activities against these Gram-negative bacteria.

N-Propargylation of Indolo-Triterpenoids and Their Application in Mannich Reaction

The introduction of the alkynyl moiety to the triterpenic core through a linkage to the indole nitrogen is described. The reaction of N-propargylindoles with N-methylpiperazine using Mannich reaction led to propargylaminoalkynyl-triterpenoids, whose structures were established by NMR spectroscopy.