In Vitro Evaluation of the Antimicrobial Ability and Cytotoxicity on Two Melanoma Cell Lines of a Benzylamide Derivative of Maslinic Acid

Progress in Antimelanoma Research of Natural Triterpenoids and Their Derivatives: Mechanisms of Action, Bioavailability Enhancement and Structure Modifications

Melanoma is one of the most dangerous forms of skin cancer, characterized by early metastasis and rapid development. In search for effective treatment options, much attention is given to triterpenoids of plant origin, which are considered promising drug candidates due to their well described anticancer properties and relatively low toxicity. This paper comprehensively summarizes the antimelanoma potential of natural triterpenoids, that are also used as scaffolds for the development of more effective derivatives. These include betulin, betulinic acid, ursolic acid, maslinic acid, oleanolic acid, celastrol and lupeol. Some lesser-known triterpenoids that deserve attention in this context are 22β-hydroxytingenone, cucurbitacins, geoditin A and ganoderic acids. Recently described mechanisms of action are presented, together with the results of preclinical in vitro and in vivo studies, as well as the use of drug delivery systems and pharmaceutical technologies to improve the bioavailability of triterpenoids. This paper also reviews the most promising structural modifications, based on structure-activity observations. In conclusion, triterpenoids of plant origin and some of their semi-synthetic derivatives exert significant cytotoxic, antiproliferative and chemopreventive effects that can be beneficial for melanoma treatment. Recent data indicate that their poor solubility in water, and thus low bioavailability, can be overcome by complexing with cyclodextrins, or the use of nanoparticles and ethosomes, thus making these compounds promising antimelanoma drug candidates for further development.

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.

Green Synthesis of Silver Nanoparticles Using Populi gemmae Extract: Preparation, Physicochemical Characterization, Antimicrobial Potential and In Vitro Antiproliferative Assessment

Green route is an economic, facile and eco-friendly method, employed for the synthesis of various types of nanoparticles, having it as a starting point biological entity, especially as a plant extract. The present study aims to obtain silver nanoparticles (AgNPs) starting from an ethanolic extract of Populi gemmae (Pg), by adjusting the reaction parameters. The morphological and structural characterization exhibited that both the reaction temperature and the concentration of metal salt, contributes to the obtaining of Pg-AgNPs with adjustable size and shape. The newly synthesized nanoparticles exhibited a good antibacterial activity on Gram-positive bacteria as well as antifungal activity. The in vitro antiproliferative activity of Pg-AgNPs was assessed on two different cancer cell lines (breast cancer cells-MCF7 and lung carcinoma epithelial cells-A549). Results have shown that the green-synthetized Pg-AgNPs_S2 (obtained at 60 °C, using AgNO3 of 5 M) induced a substantial decrease in tumor cell viability in a dose-dependent manner with an IC50 ranging from 5.03 to 5.07 µg/mL on A549 cell line and 3.24 to 4.93 µg/mL on MCF7 cell line.

The Anticancer Potential of Maslinic Acid and Its Derivatives: A Review

Cancer is still an insurmountable problem for humans and critically attacking human health. In recent years, natural products have gained increasing attention in the field of anti-tumor due to their extensive sources and minimal side effects. Maslinic acid (MA), a pentacyclic triterpene acid mainly derived from the olive tree (Olea europaea L.) has been confirmed to possess great anti-cancer effects. This paper reviewed the inhibitory effect of MA and its derivatives on lung cancer, colon cancer, ovarian cancer, gastric cancer, lymphatic, leukemia, breast cancer, pancreatic cancer, melanoma, prostate cancer, renal cell carcinoma, gallbladder cancer, and bladder cancer, among others. MA inhibited the proliferation of various tumor cells and showed lower IC50 values in melanoma 518A2 cells and gastric cancer MKN28 cells compared with other cell lines. A series of semi-synthetic derivatives obtained by modifying MA chemical structure have been shown to have high cytotoxicity to human tumor cell lines, but low cytotoxicity to non-malignant cells, which is conducive to developing its potential as a chemotherapeutic agent. These studies suggest that MA derivatives have broad prospects in the development of antitumor therapeutics in the future and warrant further study.

Advances in Research on the Preparation and Biological Activity of Maslinic Acid

Maslinic acid, a pentacyclic triterpene acid, is mainly isolated from olives. Maslinic acid and its derivatives exhibit a broad range of biological properties, such as anti-inflammatory, anticancer, anti-diabetic, antimicrobial, neuroprotective and hepatoprotective activities. In this minireview, the progress of research on maslinic acid with regard to its bioactivities, extraction, semisynthetic preparation and patents is reported. The relationships between the structure and the activity of maslinic acid and its derivatives are also discussed.

Betulinic acid derived amides are highly cytotoxic, apoptotic and selective

Betulinic and platanic acid derived amides were prepared and screened for their cytotoxic activity. All of the compounds were shown to be cytotoxic for a panel of human tumor cell lines, and especially apoptotic betulinic acid derived compounds 6, 8 and 19 showed low EC₅₀ values. Of special interest was a 4-isoquinolinyl amide of 3-O-acetyl-betulinic acid (compound 19), being the most cytotoxic compound of this series and holding EC₅₀ values as low as EC₅₀ = 1.48 μM (A375 melanoma cells) while being significantly less cytotoxic for non-malignant fibroblasts NIH 3T3 with a selectivity index of >91.2. This finding parallels previous results obtained for SAA21, a augustic acid derived compound thus making the 4-isoquinolinyl moiety to a privileged scaffold.

Phytochemical and Biological Screening of Oenothera Biennis L. Hydroalcoholic Extract

Oenothera biennis L. (OB), also commonly known as evening primrose, belongs to the Onagraceae family and has the best studied biological activity of all the members in the family. In therapy, the most frequently used type of extracts are from the aerial part, which are the fatty oils obtained from the seeds and have a wide range of medicinal properties. The aim of this study was to evaluate the phytochemical composition and biological activity of OB hydroalcoholic extract and to provide directions for the antimicrobial effect, antiproliferative and pro-apoptotic potential against A375 melanoma cell line, and anti-angiogenic and anti-inflammatory capacity. The main polyphenols and flavonoids identified were gallic acid, caffeic acid, epicatechin, coumaric acid, ferulic acid, rutin and rosmarinic acid. The total phenolic content was 631.496 µgGAE/mL of extract and the antioxidant activity was 7258.67 μmolTrolox/g of extract. The tested extract had a mild bacteriostatic effect on the tested bacterial strains. It was bactericidal only against Candida spp. and S. aureus. In the set of experimental conditions, the OB extract only manifested significant antiproliferative and pro-apoptotic activity against the A375 human melanoma cell line at the highest tested concentration, namely 60 μg/mL. The migration potential of A375 cells was hampered by the OB extract in a concentration-dependent manner. Furthermore, at the highest tested concentration, the OB extract altered the mitochondrial function in vitro, while reducing the angiogenic reaction, hindering compact tumor formation in the chorioallantoic membrane assay. Moreover, the OB extract elicited an anti-inflammatory effect on the experimental animal model of ear inflammation.

Novel Oleanolic and Maslinic Acid Derivatives as a Promising Treatment against Bacterial Biofilm in Nosocomial Infections: An in Vitro and in Vivo Study

Oleanolic acid (OA) and maslinic acid (MA) are pentacyclic triterpenic compounds that abound in industrial olive oil waste. These compounds have renowned antimicrobial properties and lack cytotoxicity in eukaryotic cells as well as resistance mechanisms in bacteria. Despite these advantages, their antimicrobial activity has only been tested in vitro, and derivatives improving this activity have not been reported. In this work, a set of 14 OA and MA C-28 amide derivatives have been synthesized. Two of these derivatives, MA-HDA and OA-HDA, increase the in vitro antimicrobial activity of the parent compounds while reducing their toxicity in most of the Gram-positive bacteria tested, including a methicillin-resistant Staphylococcus aureus-MRSA. MA-HDA also shows an enhanced in vivo efficacy in a Galleria mellonella invertebrate animal model of infection. A preliminary attempt to elucidate their mechanism of action revealed that these compounds are able to penetrate and damage the bacterial cell membrane. More significantly, their capacity to reduce antibiofilm formation in catheters has also been demonstrated in two sets of conditions: a static and a more challenged continuous-flow S. aureus biofilm.

Evaluation of essential oil obtained from Mentha×piperita L. against multidrug-resistant strains

Background

Bacterial multidrug resistance currently poses an increasingly serious threat, with important clinical consequences regarding treatment options. In 2017, the WHO released a global list of resistant bacteria, identifying multidrug-resistant (MDR) Gram-negative bacteria such as carbapenem-resistant Enterobacteriaceae, Pseudomonas aeruginosa or Acinetobacter baumannii, extended-spectrum cephalosporin-resistant Enterobacteriaceae as critical priorities for developing new strategies of treatment.

Purpose

The novelty presented in this study refers to the evaluation of the volatile oil obtained from the leaves of Mentha×piperita L., on MDR strains from hospitalized patients.

Material and methods

The essential oil was extracted by steam distillation and tested on six reference bacterial strains and also on the MDR strains collected from patients of the “Pius Brînzeu” Emergency Clinical County Hospital Timișoara. The in vitro antibacterial activity was evaluated by agar disk diffusion method and microdilution method.

Results

Testing the antibacterial activity of peppermint oil on both reference strains and isolated MDR strains from hospitalized patients demonstrated its bactericidal effect. Minimum inhibitory concentration (MIC) was lower (20 mg/mL) for Staphylococcus aureus, Escherichia coli and Proteus mirabilis and higher (40 mg/mL) for Klebsiella pneumoniae, Pseudomonas aeruginosa and Acinetobacter baumannii strains. Minimum bactericidal concentration (MBC) was equal to MIC, with the exception of Pseudomonas aeruginosa strains, where MBC was the double of MIC.

Conclusion

The present study highlights the bactericidal activity of Mentha×piperita L. essential oil on all tested MDR or extensively drug-resistant Gram-positive and Gram-negative strains of Staphylococcus aureus, Escherichia coli, Klebsiellapneumoniae, Proteus mirabilis, Pseudomonas aeruginosa and Acinetobacter baumannii. This oil may be a therapeutic option in the near future for many infectious diseases produced by MDR bacteria.

Madecassic Acid Derivatives as Potential Anticancer Agents: Synthesis and Cytotoxic Evaluation

A series of novel madecassic acid (1) derivatives was synthesized, and their cytotoxicity was evaluated against the NCI-60 panel of cancer cell lines. Several analogues exhibited broad-spectrum cytotoxic activities over all nine tumor types represented in the panel, with more potent antiproliferative activities observed against selected cancer cell lines, including multidrug-resistant phenotypes. Among them, compound 29 showed GI50 (50% growth inhibition) values ranging from 0.3 to 0.9 μM against 26 different tumor cell lines and selectivity for one colon (COLO 205) and two melanoma (SK-MEL-5 and UACC-257) cell lines at the TGI (total growth inhibition) level. The mode of action of 29 was predicted by CellMiner bioinformatic analysis and confirmed by biochemical and cell-based experiments to involve inhibition of the DNA replication process, particularly the initiation of replication, and disruption of mitochondrial membrane potential. The present findings suggest this novel madecassic acid derivative may have potential as an anticancer therapeutic lead for both solid and hematological tumors.

Assessment of the Antiangiogenic and Anti-Inflammatory Properties of a Maslinic Acid Derivative and its Potentiation using Zinc Chloride

Maslinic acid is a pentacyclic triterpene with a plethora of biological activities, including anti-inflammatory, antioxidant, antimicrobial, cardioprotective, and antitumor effects. New derivatives with improved properties and broad-spectrum activity can be obtained following structural changes of the compound. The present study was aimed to characterize a benzylamide derivative of maslinic acid—benzyl (2α, 3β) 2,3-diacetoxy-olean⁻12-en-28-amide (EM2)—with respect to the anti-angiogenic and anti-inflammatory effects in two in vivo experimental models. Consequently, the compound showed good tolerability and lack of irritation in the chorioallantoic membrane assay with no impairment of the normal angiogenic process during the tested stages of development. In the acute ear inflammation murine model, application of EM2 induced a mild anti-inflammatory effect that was potentiated by the association with zinc chloride (ZnCl₂). A decrease in dermal thickness of mice ears was observed when EM2 and ZnCl₂ were applied separately or in combination. Moreover, hyalinization of the dermis appeared only when EM2 was associated with ZnCl₂, strongly suggesting the role of their combination in wound healing.

Maslinic Acid Enhances Immune Responses in Leukemic Mice Through Macrophage Phagocytosis and Natural Killer Cell Activities In Vivo

BACKGROUND/AIM

Maslinic acid (MA), a pentacyclic triterpene extracted from wax-like coatings of olives, has been shown to reduce cancer cell number through induction of autophagy and apoptosis in many human cancer cells including human leukemia HL-60 cells. In the present study, we investigated whether or not MA affects immune responses in a leukemia mouse model.

MATERIALS AND METHODS

WEHI-3 cells were intraperitonealIy (i.p.) injected into normal BALB/c mice to develop leukemia. Mice were then treated by i.p. injection with MA at different doses (0, 8, 16 and 32 mg/kg) for 2 weeks. After treatment, all animals were weighed and blood, liver and spleen tissues were weighed. Blood or spleen both were used for determination of cell markers or phagocytosis, natural killer (NK) cell activities and T- and B-cell proliferation, respectively, by using a flow cytometric assay.

RESULTS

MA did not significantly affect body, liver, and spleen weights. However, MA increased markers of T-cells (at 16 mg/kg treatment) and monocytes (at 32 mg/kg treatment), but reduced B-cell markers (at 8 mg/kg treatment); MA did not significantly affect cell marker of macrophages. Furthermore, MA increased phagocytosis by macrophages from peripheral blood mononuclear cells and peritoneal cavity at 32 mg/kg treatment and increased NK cell activity at target cell:splenocyte ratio of 25:1 but did not affect B- and T-cell proliferation.

CONCLUSION

MA increased immune responses by enhancing macrophage phagocytosis and NK cell activities in leukemic mice.

Phytochemical Characterization and Evaluation of the Antimicrobial, Antiproliferative and Pro-Apoptotic Potential of Ephedra alata Decne. Hydroalcoholic Extract against the MCF-7 Breast Cancer Cell Line

Ephedra alata Decne. belongs to the Ephedraceae family. It is a species of Ephedra that grows mostly in the desert. Today, the main importance of Ephedra species in the medical field is due to the presence of the alkaloids derived from phenyl-alanine, which act on the sympathetic nervous system as a sympathomimetic. The aim of this study was to conduct a phytochemical characterization of the hydroalcoholic extract of the aerial part of Ephedra alata Decne., which is indigenous to Tunis, that involves the total phenolic content, individual phenolic content, and antioxidant activity as well as a biological screening for the evaluation of the antimicrobial, antifungal, antiproliferative, pro-apoptotic, and cytotoxic potential against the MCF-7 breast cancer cell line. The results show that the hydroalcoholic extract contains polyphenolic phytocompounds (156.226 ± 0.5 mgGAE/g extract) and elicits antioxidant activity (7453.18 ± 2.5 μmol Trolox/g extract). The extract acted as a bacteriostatic agent against all tested bacterial strains, but was bactericidal only against the Gram-positive cocci and Candida spp. In the set experimental parameters, the extract presents antiproliferative, pro-apoptotic, and cytotoxic potential against the MCF-7 human breast cancer cell line.

Phytochemical screening and biological activity of Lamiaceae family plant extracts

The current study aimed to investigate ethanolic extracts from the following medicinal plant species cultivated in western Romania: Melissa officinalis L., Rosmarinus officinalis L. (RO) and Salvia officinalis L. (SO). Antioxidant activity, total phenolics content and a profile of the main hydroxycinnamic acids (HCAs), including caffeic, ferulic, coumaric and rosmarinic acids, was determined for each plant extract. The in vitro antimicrobial activity against four bacterial strains (Escherichia coli, Listeria-, Pseudomonas aeruginosa and Staphylococcus aureus), and the effect on cell viability in two melanoma cell lines (B164A5 murine melanoma and A375 human melanoma) was also assessed. The results indicated that total phenolics content was 73.76-274.73 mg GAE·g-1 and the antioxidant activity was 2.32-2.87 mM Fe2+·100 g-1. There was found a strong positive correlation (R=0.9691) between total phenolics content and the antioxidant activity in the investigated samples. Regarding the HCA profile obtained by high performance liquid chromatography, the results demonstrated that rosmarinic acid represents the main identified compound. The ethanolic extracts of RO and SO exhibited antibacterial activity against Gram positive and Gram negative bacteria. RO was the most effective in terms of decreasing the cell viability of murine and human melanoma cell lines, while the HCAs did not exhibit any effect on cell viability. These findings suggest that plant extracts from the Lamiaceae family may used in the clinic as natural antibacterial agents.

Maslinic acid promotes autophagy by disrupting the interaction between Bcl2 and Beclin1 in rat pheochromocytoma PC12 cells

Maslinic acid (2α, 3β-dihydroxyolean-12-en-28-oic acid, MA) was isolated from natural plants and showed anti-cancer activity in rat Pheochromocytoma PC12 cells in our previous studies. We now discover that MA disrupts the interaction between Bcl2 and autophagy scaffold protein Beclin1 in the above cell line, leading to the up-regulation of autophagy. We investigated the effect of MA on the interaction between Bcl2 and Beclin1 by biochemical and biophysical methods in combination with autophagy characterization in the above cell line. Our results suggest that MA may serve as an autophagy activator by directly blocking the Bcl2-Beclin1 interaction to release free Beclin1 required for the recruitment of autophagy positive regulators, implying MA may exert its anti-cancer activity by regulating autophagy.

Maslinic acid suppresses the growth of human gastric cells by inducing apoptosis via inhibition of the interleukin-6 mediated Janus kinase/signal transducer and activator of transcription 3 signaling pathway

The present study aimed to determine whether maslinic acid effectively inhibits the proliferation of MKN28 cells, and to investigate the mechanisms underlying its antitumor functions. MKN28 cell viability was evaluated using a Cell Counting Kit-8, cell proliferation was analyzed by a colony formation assay and flow cytometry was used to investigate the rate of apoptosis. Western blot analysis was performed in order to determine the differential expression levels of Janus kinase (JAK), signal transducer and activator of transcription 3 (STAT3) and apoptosis associated proteins B-cell lymphoma 2 (Bcl-2), Bcl-2 associated X protein (Bax) and Bcl-2 associated agonist of cell death (Bad). Interleukin-6 (IL-6) concentration was evaluated using ELISA. IL-6 and anti-IL-6 antibodies were used to investigate the role of IL-6 in MKN28 cells treated with maslinic acid proliferation, and the STAT3 phosphorylation rates. The results demonstrated that maslinic acid treatment significantly reduced cell proliferation, induced apoptosis and was accompanied by a significant decrease in Bcl-2, Bax and Bad expression levels. Maslinic acid treatment also resulted in the downregulation of phosphorylated-STAT3 and JAK2, and significantly inhibited the protein expression of IL-6. Maslinic acid is able to inhibit MKN28 cell proliferation and the phosphorylation of STAT3 by downregulating the expression of IL-6. These results suggest that maslinic acid suppresses the growth of MKN28 cells by inducing apoptosis via its inhibition of the IL-6/JAK/STAT3 signaling cascade.