The C-3, C-17 and C-22 congeners of pentacyclic triterpenoids reduced lantadene A (3), B (4) and 22β-hydroxyoleanolic acid (5) were synthesized and were tested in vitro for their NF-κB and IKKβ inhibitory potencies and cytotoxicity against A549 lung cancer cells. The lead congeners 12 and 13 showed IC50 of 0.56 and 0.42 μmol, respectively against TNF-α induced activation of NF-κB. The congeners 12 and 13 exhibited inhibition of IKKβ in a single-digit micromolar dose and at the same time, 12 and 13 showed marked cytotoxicity against A549 lung cancer cells with IC50 of 0.12 and 0.08 μmol, respectively. The lead ester congeners were stable in the acidic pH, while hydrolyzed readily in the human blood plasma to release the active parent moieties.
A natural pentacyclic triterpenoid oleanolic acid 1 and its biotransformed metabolites 2-3 are potential α-glucosidase inhibitors. To elucidate the inhibitory mechanism of compounds 1, 2 and 3 against α-glucosidase, we calculated (i) their electronic and optical properties using DFT and TD-DFT at the B3LYP/6-31G(d) level in gas and IEF-PCM solvent; and (ii) their binding energies to α-glucosidase via docking study. DFT results showed that the α-glucosidase inhibtion is mainly depend on the polarity parameters of the studied compounds. Docking results revealed that the activity increased with binding energies (i.e. the stability of ligand-receptor complex). The specroscopic data of oleanolic acid 1 and its metabolites 2 and 3 are well predicetd for 13C NMR chemical shifts (R2=99%) and 1H NMR chemical shifts (R2=90%); and for (ii) UV/vis spectra. The assignments and interpretation of NMR chemical shifts and bathochromic shift of λMAX absorption bands are discussed.
A new triterpene, malaytaraxerate (1), and four known compounds, taraxerol (2), taraxerone (3), docosyl isoferulate (4) and docosanoic acid 2',3'-dihydroxypropyl ester (5), were isolated from the acetone extract of Sapium baccatum stem bark. The structures of the isolated compounds were determined using several spectroscopic methods, including UV-Vis, FT-IR, 1D and 2D NMR, and mass spectrometry. Major isolated compounds were assayed for cytotoxicity. The chemotaxonomic significance of this plant was also studied.
An isomeric mixture of α,β-amyrin (triterpene) and 2-methoxy-6-undecyl-1,4-benzoquinone (quinone) isolated from the Ardisia crispa root hexane (ACRH) extract was reported to possess anti-inflammatory properties in vivo. Considering the close association between inflammation and cancer, on top of the lack of antitumour study on those compounds, this study aimed to determine the potential of both compounds against tumour promotion in vitro, either as single agent or in combination. Triterpene and quinone compounds, as well as triterpene-quinone fraction (TQF) and ACRH were subjected to inhibition of Epstein-Barr virus-early antigen (EBV-EA) activation assay for that purpose. Compared with curcumin (positive control), inhibition against EBV-EA activation occurred in the order: ACRH>TQF ≥ curcumin>α,β-amyrin ≥ 2-methoxy-6-undecyl-1,4-benzoquinone. These findings reported, for the first time, the antitumor-promoting effect of α,β-amyrin and 2-methoxy-6-undecyl-1,4-benzoquinone from the roots of A. crispa, which was enhanced when both compounds act in synergy.
Lantadenes are pentacyclic triterpenoids present in the leaves of the plant Lantana camara. In the present study, in vitro antioxidant activity and free radical scavenging capacity of lantadene A was evaluated using established in vitro models such as ferric reducing antioxidant power (FRAP), 2,2-diphenyl-1-picryl-hydrazyl (DPPH•), hydroxyl radical (OH•), nitric oxide radical (NO•), superoxide anion scavenging activities and ferrous ion chelating assay. Interestingly, lantadene A showed considerable in vitro antioxidant, free radical scavenging capacity activities in a dose dependant manner when compared with the standard antioxidant in nitric oxide scavenging, superoxide anion radical scavenging and ferrous ion chelating assay. These findings show that the lantadene A possesses antioxidant activity with different mechanism of actions towards the different free radicals tested. Since lantadene A is a very popular drug in modern medicine, it is a promising candidate for use as an antioxidant and hepatoprotective agent.
The aim of the present study was to evaluate the hepatoprotective activity of lantadene A against acetaminophen-induced liver toxicity in mice was studied. Activity was measured by monitoring the levels of aspartate aminotransferase (AST), alanine aminotransferase (ALT), alkaline phosphatase (ALP) and bilirubin, along with histo-pathological analysis. Silymarin was used as positive control. A bimodal pattern of behavioural toxicity was exhibited by the lantadene A-treated group at the beginning of the treatment. However, treatment with lantadene A and silymarin resulted in an increase in the liver weight compared with the acetaminophen treated group. The results of the acetaminophen-induced liver toxicity experiments showed that mice treated with lantadene A (500 mg/kg) showed a significant decrease in the activity of ALT, AST and ALP and the level of bilirubin, which were all elevated in the acetaminophen treated group (p < 0.05). Histological studies supported the biochemical findings and a maximum improvement in the histoarchitecture was seen. The lantadene A-treated group showed remarkable protective effects against histopathological alterations, with comparable results to the silymarin treated group. The current study confirmed the hepatoprotective effects of lantadene A against the model hepatotoxicant acetaminophen, which is likely related to its potent antioxidative activity.
The evolution of antibiotic resistance in Staphylococcus aureus showed that there is no long-lasting remedy against this pathogen. The limited number of antibacterial classes and the common occurrence of cross-resistance within and between classes reinforce the urgent need to discover new compounds targeting novel cellular functions not yet targeted by currently used drugs. One of the experimental approaches used to discover novel antibacterials and their in vitro targets is natural product screening. Three known pentacyclic triterpenoids were isolated for the first time from the bark of Callicarpa farinosa Roxb. (Verbenaceae) and identified as α-amyrin [3β-hydroxy-urs-12-en-3-ol], betulinic acid [3β-hydroxy-20(29)-lupaene-28-oic acid], and betulinaldehyde [3β-hydroxy-20(29)-lupen-28-al]. These compounds exhibited antimicrobial activities against reference and clinical strains of methicillin-resistant (MRSA) and methicillin-sensitive S. aureus (MSSA), with minimum inhibitory concentration (MIC) ranging from 2 to 512 μg/mL. From the genome-wide transcriptomic analysis to elucidate the antimicrobial effects of these compounds, multiple novel cellular targets in cell division, two-component system, ABC transporters, fatty acid biosynthesis, peptidoglycan biosynthesis, aminoacyl-tRNA synthetases, ribosomes and β-lactam resistance pathways are affected, resulting in destabilization of the bacterial cell membrane, halt in protein synthesis, and inhibition of cell growth that eventually lead to cell death. The novel targets in these essential pathways could be further explored in the development of therapeutic compounds for the treatment of S. aureus infections and help mitigate resistance development due to target alterations.
The new series of pentacyclic triterpenoids reduced lantadene A (3), B (4), and 22β-hydroxy-3-oxo-olean-12-en-28-oic acid (5) analogs were synthesized and tested in vitro for their NF-κB and IKKβ inhibitory potencies and cytotoxicity against A549 lung cancer cells. The lead analog (11) showed sub-micromolar activity against TNF-α induced activation of NF-κB and exhibited inhibition of IKKβ in a single-digit micromolar dose. At the same time, 11 showed promising cytotoxicity against A549 lung cancer cells with IC50 of 0.98 μM. The Western blot analysis further showed that the suppression of NF-κB activity by the lead analog 11 was due to the inhibition of IκBα degradation, a natural inhibitor of NF-κB. The physicochemical evaluation demonstrated that the lead analog 11 was stable in the simulated gastric fluid of pH 2, while hydrolyzed at a relatively higher rate in the human blood plasma to release the active parent moieties. Molecular docking analysis showed that 11 was hydrogen bonded with the Arg-31 and Gln-110 residues of the IKKβ.