Antioxidant and cytotoxic activity of new di- and polyamine caffeine analogues

Evaluation of Antioxidant and Anti-Inflammatory Activities, and Metabolite Profiling of Selected Medicinal Plants of Nepal

This study aimed to evaluate the antioxidant, antiarthritic, and anti-inflammatory properties of extracts from the leaves of twelve different medicinal plants in Nepal. We then evaluated the total phenolic, flavonoid, and tannin contents of the extract using in-vitro assays and characterized it using GC-MS analysis. Results revealed that most of the leaf extracts contained phenolic compounds, flavonoids, tannins, alkaloids, and saponins. Few plants also showed the presence of glycosides, phytate, and vitamin C. Among the studied plants, Neolamarckia cadamba exhibited the highest total phenolic and tannin contents, as 241.53 ± 0.20 µg of gallic acid equivalent/mg and 74.48 ± 1.081 µg of tannic acid equivalent/mg, respectively. Ipomoea batatas exhibited the highest total flavonoid content, as 53.051 ± 1.11 µg of quercetin equivalent/mg. Moreover, Raphanus sativus demonstrated significant ferrous ion chelating, 2,2-diphenyl-1-picrylhydrazyl, hydrogen peroxide scavenging, and total antioxidant activities with IC50 value of 4.76 ± 0.68 µg/mL, 5.84 ± 0.14 µg/mL, 6.89 ± 0.16 µg/mL, and 8.99 ± 0.20 µg/mL, respectively. Similarly, Colocasia esculenta and Cicer arietinum exhibited the highest hydroxyl radical and nitric oxide scavenging activities, measuring IC50 value of 7.22 ± 0.56 µg/mL and 9.06 ± 0.10 µg/mL, respectively. Among all the extracts, Amorphophallus paeoniifolius displayed significant human red blood cell (HRBC) membrane stabilization activity (IC50 = 6.22 ± 0.78 µg/mL). Furthermore, Raphanus sativus, Chenopodium album, Cicer arietinum, and Murraya koenigii exhibited the highest inhibitory activities against protein denaturation with bovine serum albumin, antiarthritic, lipoxygenase inhibitory, and proteinase inhibitory, measuring IC50 of 7.48 ± 0.48 µg/mL, 9.44 ± 1.62 µg/mL, 14.67 ± 1.94 µg/mL, and 28.57 ± 2.39 µg/mL, respectively. In conclusion, this study demonstrated the twelve leaf extracts' significant antioxidant, antiarthritic, and anti-inflammatory activities.

New C8-substituted caffeine derivatives as promising antioxidants and cytoprotective agents in human erythrocytes

New structurally diverse groups of C8-substituted caffeine derivatives were synthesized and evaluated for their chemical and biological properties. Mass spectrometry, FT-IR, and NMR characterizations of these derivatives were performed. The cytotoxic activity of the derivatives was estimated in vitro using human red blood cells (RBC) and in silico pharmacokinetic studies. The antioxidant capacity of the compounds was analyzed using a ferrous ion chelating activity assay. The ability of the derivatives to protect RBC from oxidative damage, including the oxidation of hemoglobin to methemoglobin, was assessed using a water-soluble 2,2'-azobis(2-methyl-propionamidine) dihydrochloride (AAPH) as a standard inducer of peroxyl radicals. The level of intracellular oxidative stress was assessed using the fluorescent redox probe 2',7'-dichlorodihydrofluorescein diacetate (DCF-DA). The results indicate that all derivatives are biocompatible compounds with significant antioxidant and cytoprotective potential dependent on their chemical structure. In order to explain the antioxidant and cytoprotective activity of the derivatives, a mechanism of hydrogen atom transfer (HAT), radical adduct formation (RAF), or single electron transfer (SET), as well as the specific interactions of the derivatives with the lipid bilayer of RBC membrane, have been proposed. The results show that selected modifications of the caffeine molecule enhance its antioxidant properties, which expands our knowledge of the structure-activity relationship of caffeine-based cytoprotective compounds.

Synthesis, antioxidant and cytoprotective activity evaluation of C-3 substituted indole derivatives

A series of fifteen indole derivatives substituted at the C-3 position were synthesized and characterized. The antioxidant activity of all derivatives was investigated by three in vitro antioxidant assays, and the derivative with pyrrolidinedithiocarbamate moiety was the most active as a radical scavenger and Fe³⁺-Fe²⁺ reducer. It can be stated that possible hydrogen and electron transfer mechanism is suggested for the quenching of the free radical. Moreover, the indolyl radical stabilization and the presence of unsubstituted indole nitrogen atom are mandatory for the observed antioxidant activity, which strongly depends on the type of the substituent directly connected to the methylene group at the C-3 position. Human red blood cells (RBC) have been used as a cell model to study derivatives interaction with the cell membrane. Haemolytic activity and RBC shape transformation were observed for certain derivatives in a concentration-dependent manner. However, most of the derivatives at sublytic concentration showed high cytoprotective activity against oxidative haemolysis induced by 2,2′-azobis(2-methylpropionamidine) dihydrochloride (AAPH). The cytoprotective properties of derivatives can be explained mostly due to their interactions with the RBC membrane components. Taking together, theoretical estimations and experimental data confirm the beneficial interactions between the selected C-3 substituted indole derivatives and the RBC membrane under oxidative stress conditions. These results encourage us to further structural optimization of C-3 substituted indole derivatives as potent antioxidant compounds.

Effect of the Solvent on Propolis Phenolic Profile and its Antifungal, Antioxidant, and In Vitro Cytoprotective Activity in Human Erythrocytes Under Oxidative Stress

Propolis is a natural bee product with various beneficial biological effects. The health-promoting properties of propolis depend on its chemical composition, particularly the presence of phenolic compounds. The aim of this study was to evaluate the relationship between extraction solvent (acetone 100%, ethanol 70% and 96%) and the antifungal, antioxidant, and cytoprotective activity of the extracts obtained from propolis. Concentrations of flavonoids and phenolic acids in the propolis extracts were determined using ultrahigh-performance liquid chromatography. The antioxidant potential of different extracts was assessed on the basis of 2,2-diphenyl-1-picrylhydrazyl (DPPH·) free-radical-scavenging activity, Fe³⁺-reducing power, and ferrous ion (Fe²⁺)-chelating activity assays. The ability of the extracts to protect human red blood cell membranes against free-radical-induced damage and their antifungal activity was also determined. The results showed that the concentration of flavonoids in the propolis extracts was dependent on the solvent used in the extraction process and pinocembrin, chrysin, galangin, and coumaric acid were the most abundant phenols. All extracts exhibited high antioxidant potential and significantly protected human erythrocytes against oxidative damage. On the other hand, the antifungal activity of the propolis extracts depended on the solvent used in extraction and the fungal strains tested. It needs to be stressed that, to the best of our knowledge, there is no study relating the effect of solvent used for extraction of Polish propolis to its phenolic profile, and its antifungal, antioxidant, and cytoprotective activity.

Rhubarb-Aconite Decoction (RAD) Drug-Containing Serum Alleviated Endotoxin-Induced Oxidative Stress Injury and Inflammatory Response in Caco-2 Cells In Vitro

Rhubarb-Aconite Decoction (RAD), a famous Chinese medicine prescription, has been widely used for treating intestinal injury. However, the effect of RAD on intestinal epithelial cells is unclear. The aim of this study was to investigate the effects of RAD drug-containing serum on the oxidative stress injury and inflammatory response induced by endotoxin (ET) in Caco-2 cells in vitro. Lipid peroxide malondialdehyde (MDA), lactate dehydrogenase (LDH), caspase-11, tumor necrosis factor-α(TNF-α), interleukin-3(IL-3), and cytokeratin (CK)18, adenosine triphosphate (ATP) activity, and intracellular free calcium ion levels were measured. The results showed that ET triggered the activation of caspase-11 and the massive release of TNF-α, increased the inhibitory rate of cell growth, MDA, and LDH expressions in Caco-2 cells. Moreover, RAD drug-containing serum could inhibit caspase-11 activation, decrease the release of TNF-α and IL-3, reduce intracellular free calcium ion, and enhance CK 18 expression and ATP activity. These novel findings demonstrated that ET-induced oxidative stress injury and inflammatory response of Caco-2 cells were improved by RAD drug-containing serum, indicating that RAD may be a good choice for the treatment of intestinal injury.

The Effect of Bee Venom Peptides Melittin, Tertiapin, and Apamin on the Human Erythrocytes Ghosts: A Preliminary Study

Red blood cells (RBCs) are the most abundant cells in the human blood that have been extensively studied under morphology, ultrastructure, biochemical and molecular functions. Therefore, RBCs are excellent cell models in the study of biologically active compounds like drugs and toxins on the structure and function of the cell membrane. The aim of the present study was to explore erythrocyte ghost’s proteome to identify changes occurring under the influence of three bee venom peptides-melittin, tertiapin, and apamin. We conducted preliminary experiments on the erythrocyte ghosts incubated with these peptides at their non-hemolytic concentrations. Such preparations were analyzed using liquid chromatography coupled with tandem mass spectrometry. It was found that when higher concentrations of melittin and apamin were used, fewer proteins were identified. Moreover, the results clearly indicated that apamin demonstrates the greatest influence on the RBCs ghosts proteome. Interestingly, the data also suggest that tertiapin exerted a stabilizing effect on the erythrocyte membrane. The experiments carried out show the great potential of proteomic research in the projects focused on the toxin’s properties as membrane active agents. However, to determine the specificity of the effect of selected bee venom peptides on the erythrocyte ghosts, further proteomic research should be focused on the quantitative analysis.

Identification and Characterization of the Tyrosinase Inhibitory Activity of Caffeine from Camellia Pollen

Tyrosinase inhibitors are important in cosmetic, medical, and food industries due to their regulation of melanin production. A tyrosinase inhibitor was purified from Camellia pollen using high-speed countercurrent chromatography and preparative high-performance liquid chromatography and was identified as caffeine by NMR and mass spectrometry. It showed strong mushroom tyrosinase inhibitory activity with an IC₅₀ of 18.5 ± 2.31 μg/mL in a noncompetitive model. The caffeine did not interact with copper ions in the active center of the enzyme but could quench fluorescence intensity and change the secondary conformation of this tyrosinase. A molecular dynamics simulation showed that caffeine bound this tyrosinase via Lys379, Lys 376, Asp357, Glu356, Thr308, Gln307, Asp312, and Trp358, thus changing the binding sites of l-tyrosine and the loop conformation adjacent to the active center. In vitro cell model analysis revealed that caffeine exhibited significant inhibitory effects on both intracellular tyrosinase activity and melanin production of B16-F10 melanoma cells in a concentration-dependent manner. These comprehensive results suggest that caffeine is a strong tyrosinase inhibitor that has the potential to be developed as skin-whitening agents in the cosmetics and pharmaceutical industries or as antibrowning agents in the food industry.