Pterostilbene from Vitis coignetiae protect H2O2-induced inhibition of gap junctional intercellular communication in rat liver cell line

In this study, we identified various stilbenoids derived from Vitis coignetiae and investigated the protective effect of the main component, pterostilbene, against the inhibition of gap junctional intercellular communication (GJIC) induced by H₂O₂ in WB-F344 rat liver epithelial cells. We analyzed seven kinds of stilbenoids, pterostilbene, astringin, piceid, vitisin, rhaponticin, resveratrol, and rhapontigenin, using DAD/UV HPLC. Total stilbenoid content was 127.37 ± 19.29 mg/100 g dry weight. Pretreatment with 0.5, 1.0, and 5.0 μM pterostilbene for 24 h was shown to recover GJIC blocked by 500 μM H₂O₂. Pretreatment with pterostilbene prevented the inhibition of GJIC via the down-regulation of connexin43 phosphorylation by the inactivation of ERK1/2 and p38 MAP kinase. Our results suggest that pterostilbene may be a functional chemopreventative agent and that dietary exposure of pterostilbene would be helpful for improving health.     

Phenolic composition and biological activities of Juniperus drupacea Labill. berries from Turkey

The present study was designed to define the phenolic profile and the biological potential of berries methanol extract of Juniperus drupacea Labill. from Turkey.The total phenolic content (Folin-Ciocalteau assay) was 48.06 ± 0.99 mg GAE/g extract. The HPLC-DAD-ESI-MS analysis allowed the determination of the complete phenolic profile of J. drupacea berries. Phenolic acids represented more than 60% of the total phenolics, and tyrosol was the major one (1324 ± 0.64 μg/g extract); within the flavonoids amentoflavone was detected as the main constituent (927 ± 0.35 μg/g extract).The extract exhibited good antioxidant properties, as determined by different in vitro models: DPPH test (IC₅₀ 0.38 ± 0.02 mg/mL), reducing power (12.63 ± 0.14 ASE/mL), Fe²⁺ chelating ability (IC₅₀ 2.26 ± 0.06 mg/mL), and TBA test (IC₅₀ 2.47 ± 1.13 μg/mL).Cytotoxicity against Artemia salina was highlighted (LC₅₀ 489.47 ± 27.8 μg/mL), and a significant decrease (p ? 0.05; p ? 0.01) in HepG2 cells viability was observed at the higher concentrations (5-10 μg/mL).The extract displayed good antibacterial activity towards Gram-positive bacteria and in particular Staphylococcus aureus was the most susceptible strain (MIC 78.12 μg/mL).     

Scavenging capacity of strawberry tree (Arbutus unedo L.) leaves on free radicals

Despite strawberry tree (Arbutus unedo L.) leaves had a long use in traditional medicine due to its antiseptic, diuretic, astringent and depurative properties, the potential of their antioxidant activity are still lacking. Our study goals to assess the antioxidant and free radical scavenging potential of water, ethanol, methanol and diethyl ether extracts of A. unedo leaves. Total phenols content was achieved spectrophotometrically using Folin–Ciocalteau reagent with gallic acid as standard. Antioxidant activity was evaluated using three different methods: reducing power of iron (III)/ferricyanide complex assay, scavenging effect on DPPH (2,2-diphenyl-1-picrylhydrazyl) radicals and scavenging effect on superoxide radicals by using the PMS–NADH–nitroblue tetrazolium system. Ethanol extracts of A. unedo leaves were the highest in reducing power (IC₅₀ 232.7 μg/mL) and DPPH scavenging effect (IC₅₀ 63.2 μg/mL) followed by water extracts (with IC₅₀ of 287.7 and 73.7 μg/mL, respectively); whereas diethyl ether extracts were the lowest. In the scavenging on superoxide radical assay, methanol extracts obtained the best results (IC₅₀ 6.9 μg/mL). For all the methods tested the antioxidant activity was concentration dependent. In accordance with antioxidant activity, highest total phenols content were found in ethanol, followed by water, methanol and diethyl ether extract. The results indicated that A. unedo leaves are a potential source of natural antioxidants.     

Comparative analysis of the antioxidant and DNA protection capacities of Anadenanthera colubrina, Libidibia ferrea and Pityrocarpa moniliformis fruits

This study aimed to explore the antioxidant and DNA protection abilities of hydroalcoholic extracts from fruits of Anadenanthera colubrina (ACHE), Libidibia ferrea (LFHE) and Pityrocarpa moniliformis (PMHE). These extracts were tested by five antioxidant methods (phosphomolibdenium and reducing power assays; superoxide, hydrogen peroxide and nitric oxide scavenging) and DNA protection capacity. Total phenolic content was measured by Folin-Ciocalteu method. ACHE exhibited the highest phenolic content (578 mg/g GAE), followed by LFHE (460 mg/g GAE) and PMHE (448 mg/g GAE). In phosphomolibdenium assay, ACHE showed 24.81% of activity in relation to ascorbic acid, whereas LFHE and PMHE had 21.08% and 18.05%, respectively. These plants showed high ability to inhibit reactive species tested with IC50 values ranged from 10.66 to 14.37 μg/mL for superoxide radical; 26.05 to 45.43 μg/mL for hydrogen peroxide; 178.42 to 182.98 μg/mL for reducing power; and 199.2 to 283 μg/mL for nitric oxide. Furthermore, these extracts had capacity to break the DNA damage induced by hydroxyl radicals. The antioxidant activity of these plants is related with their higher phenolic content and show that they may be used as source of bioactive compounds, relevant to the maintenance of oxidative stability of the food matrix, cosmetics and/or pharmaceutical preparations.     

Antibacterial and antiparasitic effects of Bothrops marajoensis venom and its fractions: Phospholipase A2 and l-amino acid oxidase

Some proteins present in snake venom possess enzymatic activities, such as phospholipase A₂ and l-amino acid oxidase. In this study, we verify the action of the Bothrops marajoensis venom (BmarTV), PLA₂ (BmarPLA₂) and LAAO (BmarLAAO) on strains of bacteria, yeast, and Leishmania sp. The BmarTV was isolated by Protein Pack 5PW, and several fractions were obtained. Reverse phase HPLC showed that BmarPLA₂ was isolated from the venom, and N-terminal amino acid sequencing of sPLA₂ showed high amino acid identity with other lysine K49 sPLA₂s isolated from Bothrops snakes. The BmarLAAO was purified to high molecular homogeneity and its N-terminal amino acid sequence demonstrated a high degree of amino acid conservation with others LAAOs. BmarLAAO was able to inhibit the growth of P. aeruginosa, C. albicans and S. aureus in a dose-dependent manner. The inhibitory effect was more significant on S. aureus, with a MIC = 50 μg/mL and MLC = 200 μg/mL. However, the BmarTV and BmarPLA₂ did not demonstrate inhibitory capacity. BmarLAAO was able to inhibit the growth of promastigote forms of L. chagasi and L. amazonensis, with an IC₅₀ = 2.55 μg/mL and 2.86 μg/mL for L. amazonensis and L. chagasi, respectively. BmarTV also provided significant inhibition of parasitic growth, with an IC₅₀ of 86.56 μg/mL for L. amazonensis and 79.02 μg/mL for L. chagasi. BmarPLA₂ did not promote any inhibition of the growth of these parasites. The BmarLAAO and BmarTV presented low toxicity at the concentrations studied. In conclusion, whole venom as well as the l-amino acid oxidase from Bothrops marajoensis was able to inhibit the growth of several microorganisms, including S. aureus, Candida albicans, Pseudomonas aeruginosa, and Leishmania sp.     

Chemical composition,antifungal and antiaflatoxigenic activities of Ocimum sanctum L. essential oil and its safety assessment as plant based antimicrobial

The study deals with the efficacy of Ocimum sanctum essential oil (EO) and its major component, eugenol against the fungi causing biodeterioration of food stuffs during storage. O. sanctum EO and eugenol were found efficacious in checking growth of Aspergillus flavus NKDHV8; and, their minimum inhibitory concentrations (MICs) were recorded as 0.3 and 0.2 μl ml⁻¹, respectively. The O. sanctum EO and eugenol also inhibited the aflatoxin B₁ production completely at 0.2 and 0.1 μl ml⁻¹, respectively. Both of these were found superior over some prevalent synthetic antifungals and exhibited broad fungitoxic spectrum against 12 commonly occurring fungi. The LD₅₀ value of O. sanctum EO on mice was found to be 4571.43 μl kg⁻¹ suggesting its non-mammalian toxic nature. The findings of present study reveals the possible exploitation of O. sanctum EO and eugenol as plant based safe preservatives against fungal spoilage of food stuffs during storage.     

A search for hepatoprotective activity of aqueous extract of Rhus coriaria L. against oxidative stress cytotoxicity

The protective effects of different concentrations of aqueous extract of Rhus coriaria L. fruit (75 and 100 μg/ml) and also gallic acid (100 μM) as one of its main components were examined against oxidative stress toxicity induced by cumene hydroperoxide (CHP) in isolated rat hepatocytes. Both extract concentrations and gallic acid (100 μM) significantly (P < 0.05) protected the hepatocyte against all oxidative stress markers including cell lysis, ROS generation, lipid peroxidation, glutathione depletion, mitochondrial membrane potential decrease, lysosomal membrane oxidative damage and cellular proteolysis. Aqueous extracts of Rhus coriaria L. (75 and 100 μg/ml) were more effective than gallic acid (100 μM) in protecting hepatocytes against CHP induced lipid peroxidation (P < 0.05). On the other hand gallic acid (100 μM) acted more effective than aqueous extracts of Rhus coriaria L. (75 and 100 μg/ml) at preventing hepatocyte membrane lysis (P < 0.05). In addition H₂O₂ scavenging effect of both extract concentrations (75 and 100 μg/ml) were determined in hepatocytes and compared with gallic acid (100 μM). Gallic acid (100 μM) was more effective than aqueous extracts of Rhus coriaria L. (75 and 100 μg/ml) at H₂O₂ scavenging activity (P < 0.05).     

Gentiana asclepiadea exerts antioxidant activity and enhances DNA repair of hydrogen peroxide- and silver nanoparticles-induced DNA damage

Exposure to high levels of different environmental pollutants is known to be associated with induction of DNA damage in humans. Thus DNA repair is of great importance in preventing mutations and contributes crucially to the prevention of cancer. In our study we have focused on quantitative analysis of Gentiana asclepiadea aqueous or methanolic extracts obtained from flower and haulm, their antioxidant potency in ABTS post-column derivatisation, and their potential ability to enhance DNA repair in human lymphocytes after hydrogen peroxide (H₂O₂) treatment (250 μM, 5 min). We also studied DNA repair in human kidney HEK 293 cells after exposure to 20 nm silver nanoparticles (AgNPs) (100 μg/ml, 30 min) in the presence and absence of the plant extract. We have found that mangiferin along with unidentified polar compounds are the most pronounced antioxidants in the studied extracts. Extract from haulm exhibited slightly stronger antioxidant properties compared to flower extracts. However, all four extracts showed significant ability to enhance DNA repair in both cell types after H₂O₂ and AgNP treatments.     

Volatile compounds in the stem bark of Sclerocarya birrea (Anacardiaceae) possess antimicrobial activity against drug-resistant strains of Helicobacter pylori

The aim of this study was to isolate and identify phytochemicals with anti-Helicobacter pylori activity from the stem bark of Sclerocarya birrea. The plant crude extract was fractionated by silica gel column and thin layer chromatography techniques, initially with ethyl acetate (EA) and subsequently with a combination of ethyl acetate/methanol/water (EMW). Further fractionation and identification of the phytoconstituents was achieved by gas chromatography and mass spectrometry (GC/MS) analysis. The antimicrobial activity of the fractions and compounds was evaluated against five metronidazole- and clarithromycin-resistant strains of H. pylori as well as a reference strain ATCC 43526 using the microbroth dilution technique. Amoxicillin was included in the experiments as a positive control antibiotic. Of the 18 fractions collected, 16 demonstrated anti-H. pylori activity with 50% minimum inhibitory concentration (MIC₅₀) values ranging from 310 μg/mL to 2500 μg/mL. Two of the fractions (EMW fraction 6 and EA fraction 1) revealed the presence of 5 and 24 compounds, respectively, representing 40.5% and 86.57% of the total composition. Most of the compounds were essential oils, with terpinen-4-ol being the most abundant agent (35.83%), followed by pyrrolidine (32.15%), aromadendrene (13.63%) and α-gurjunene (8.77%). MIC₅₀ ranges for amoxicillin, terpinen-4-ol and pyrrolidine were 0.0003-0.06 μg/mL, 0.004-0.06 μg/mL and 0.005-6.3 μg/mL, respectively. The inhibitory activities of terpinen-4-ol and pyrrolidine were similar to amoxicillin (P > 0.05). Most of these compounds are being reported in this plant for the first time and may represent new sources of therapeutically useful compounds against H. pylori.     

In vitro and in vivo antioxidant activity of Symplocos cochinchinensis S. Moore leaves containing phenolic compounds

Methanol extract of Symplocos cochinchinensis S. Moore leaves was evaluated for its in vitro and in vivo antioxidant activity. The total phenolic content of the extract was 230 mg of gallic acid equivalents/g extract. The extract showed very good scavenging activity on 2,2-diphenyl-picrylhydrazyl (DPPH) (IC₅₀ 620.30 ± 0.14 μg/ml), hydroxyl (IC₅₀ 730.21 ± 1.05 μg/ml), nitric oxide (IC₅₀ 870.31 ± 0.19 μg/ml) radicals, as well as high reducing power. The extract also showed strong suppressive effect on lipid peroxidation. In in vivo study CCl₄ induced oxidative stress produced significant increase in SGOT, SGPT and LDH levels along with reduction in liver SOD, CAT, GSH and GPx levels. Pre-treatment of rats with the extract (250 and 500 mg/kg) for 7 days showed significant reduction in the levels of SGOT, SGPT and LDH compared to CCl₄ treated rats. SOD, CAT, GSH and GPx levels were increased significantly due to treatment with the extract. The activity of the extract was comparable to the standard drug, silymarin (25 mg/kg). The results suggest that the leaves of S. cochinchinensis are a source of natural antioxidants.     

Antioxidant and antiproliferative properties of water extract from Mahonia bealei (Fort.) Carr. leaves

Mahonia bealei (Fort.) Carr. (Berberidaceae) leaves have been widely used as a tea leaf beverage south of the Qinling Mountains of China. In this study, the antioxidant and antiproliferative properties of M. bealei leaves were investigated. Our data showed that the water extract of M. bealei leaves (WML) exhibited extremely high antioxidant properties, which were demonstrated by its ability to scavenge 50% of 1,1-diphenyll-2-2-pricylhydrazyl (DPPH) free radicals at 60.46 μg/ml, and it eliminated approximately 71.19% of superoxide radicals at 500 μg/ml. In addition, the WML showed strong reducing abilities and provided protection against oxidative protein damage induced by hydroxyl radicals. Cellular proliferation and the induction of apoptosis were also examined by cellular proliferation assay, flow cytometry, and mRNA expression analysis. These results demonstrate that WML significantly inhibited the growth of human colon cancer (HT-29) cells in a concentration-dependent manner, and it gradually increased the proportion of apoptotic cells and reduced the expression of the survivin gene. The bioactivity-guided study of WML resulted in the isolation and identification of berberine, a known isoquinoline alkaloid. Berberine exhibited strong antiproliferative activity on HT-29 cells, with IC₅₀ values of 36.54 μM, suggesting it is, in part, responsible of the anticancer activity of WML.     

Activation of phospholipase D involved in both injury and survival in A549 alveolar epithelial cells exposed to H2O2

To determine the role of the phospholipase D (PLD) pathway in injury and survival of alveolar epithelial cells, A549 cells were exposed to H₂O₂ (500 μM) which resulted in time-dependent injury and bi-phasic increase of PLD activity at 5 min and at 3 h, respectively. n-Butanol (0.5%) inhibited PLD activation, attenuated cell injury at 5 min of H₂O₂ exposure, but enhanced injury at 3 h of exposure. This activation was inhibited by treatment with catalase (500 units/ml). Exogenous phosphatidic acid mimicked the effects of PLD activation, and diphenyliodonium (NADPH oxidase inhibitor) reversed the decline in cell viability induced by H₂O₂ exposure. Propranolol (phosphatidic acid phospholydrolase inhibitor) and quinacrine (phospholipase A2 inhibitor) had weak effects on H₂O₂-induced PLD activation but reversed H₂O₂-induced injury. We speculate that PLD activation at the initiation of H₂O₂ exposure predominantly results in NAPDH oxidase activation, which mediates A549 cell injury, but turns to mediating cell survival as the H₂O₂ attack continues, which might be mainly due to the accumulation of intracellular phosphatidic acid.     

Diarylheptanoid 7-(3,4 dihydroxyphenyl)-5-hydroxy-1-phenyl-(1E)-1-heptene from Curcuma comosa Roxb. protects retinal pigment epithelial cells against oxidative stress-induced cell death

Chronic exposure to oxidative stress causes damage to retinal pigment epithelial cells which may lead to the development of age-related macular degeneration, the major cause of vision loss in humans. Anti-oxidants provide a natural defense against retinal cell damage. The present study was designed to evaluate the potential anti-oxidant activity and protective effect of two diarylheptanoids isolated from a medicinal herb Curcuma comosa; 7-(3,4 dihydroxyphenyl)-5-hydroxy-1-phenyl-(1E)-1-heptene (compound A), and 1,7-diphenyl-4(E),6(E)-heptadien-3-ol (compound B) against oxidative stress (H₂O₂)-induced human retinal pigment epithelial (APRE-19) cell death. The 2,2-diphenyl-1-picrylhydrazyl (DPPH) assay indicated that the anti-oxidant activity (IC₅₀) of compound A was similar to that of vitamin C. Pre-treatment of ARPE-19 cells with 20 μM compound A for 4 h afforded greater protection against the insult from 500 μM H₂O₂, compared to a similar protection period for compound B. Compound A lowered H₂O₂-induced lipid peroxidation, malondialdehyde formation and intracellular reactive oxygen species. Furthermore, compound A ameliorated the H₂O₂-induced decrease in anti-oxidant enzyme activities and subsequent apoptotic cell death in ARPE-19 cells in a dose and time-dependent manner. These results suggest that compound A protects ARPE-19 cells against oxidative stress, in part, by enhancing several anti-oxidant defense mechanisms. Therefore, compound A may have therapeutic potential for diseases associated with oxidative stress, particularly degenerative retinal diseases.     

In vitro antioxidant,antidiabetic and antilipidemic activities of Symplocos cochinchinensis (Lour.) S. Moore bark

Symplocos cochinchinesis is used in Indian system of traditional medicine to treat diabetes mellitus. The present study investigates the in vitro antioxidant, antidiabetic and antilipidemic activities of S. cochinchinensis bark methanolic extract (SCBe) in streptozotocin (STZ) induced diabetic rats. In in vitro studies SCBe showed very good scavenging activity on 2,2-diphenyl-picrylhydrazyl (DPPH) (IC₅₀ 820.34 ± 1.74 μg/ml), hydroxyl (IC₅₀ 884.19 ± 0.45 μg/ml) and nitric oxide (IC₅₀ 860.21 ± 1.18 μg/ml) radicals, as well as high reducing power. SCBe (250 and 500 mg/kg) was administered to STZ (40 mg/kg) induced diabetic rats for 28 days. SCBe showed a significant decrease in blood glucose and significant increase in plasma insulin and liver glycogen levels in treated diabetic rats. Further, SCBe showed antilipidemic activity as evidenced by significant decrease in serum TC, TG, LDL-C levels and significant increase in HDL-C level in treated diabetic rats. SCBe also restored the altered plasma enzymes (SGOT, SGPT and ALP), total protein, urea and creatinine levels to near normal. The action of SCBe was comparable to the antidiabetic drug glibenclamide. Results of this experimental study indicated that SCBe possessed antioxidant, antidiabetic and antilipidemic activities.     

Essential oil composition and antioxidant activities of Curcuma aromatica Salisb.

The chemical composition of the hydro-distilled essential oil from leaves of Curcuma aromatica Salisb. was analysed by GC–MS. Twenty-three compounds representing 94.29% of the total oil were identified. The antioxidant activities of the oil and various extracts of C. aromatica were evaluated by using 2,2-diphenyl-1-picrylhydrazyl (DPPH) and superoxide radical-scavenging assays. The oil and methanol extract showed potent DPPH radical-scavenging activities (IC₅₀ = 14.45 and 16.58 μg/ml, respectively), which were higher than butylated hydroxyanisole (IC₅₀ = 18.27 μg/ml). The extracts also exhibited remarkable superoxide radical-scavenging activities (IC₅₀ = 22.6–45.27 μg/ml) and the activity in the methanol extract was superior to all other extracts (IC₅₀ = 22.6 μg/ml). Furthermore, the amount of total phenolic compounds was determined and its content in ethyl acetate extract was the highest as compared to other extracts. The results indicate that the oil and extracts of C. aromatica could serve as an important bio-resource of antioxidants for using in the food industries.     

Antioxidant and antidermatophytic activities of essential oil and extracts of Metasequoia glyptostroboides Miki ex Hu

This study was undertaken to assess the antioxidant and antidermatophytic potential of the essential oil and extracts (hexane, chloroform, ethyl acetate and methanol) of Metasequoia glyptostroboides Miki ex Hu. Antioxidant activity was evaluated by using 1,1-diphenyl-2-picrylhydrazyl (DPPH) assay. The free radical scavenging activities of the oil and ethyl acetate extract were found to be superior (IC₅₀ = 9.1 and 14.24 μg/ml, respectively) as compared to butylatedhydroxyanisole (BHA), (IC₅₀ = 18.27 μg/ml). Also the ethyl acetate extract revealed the highest phenolic contents (93.26 mg/g of dry wt) as compared to the other extracts. Further, oil (1250 μg/disc) and extracts (1750 μg/disc) revealed 35.33–67.66 and 18.0–53.3% antidermatophytic effect, respectively, along with their respective MIC values (62.5–500 and 250–4000 μg/ml) against Trichophyton rubrum KCTC 6345, T. rubrum KCTC 6375, T. rubrum KCTC 6352, T. mentagrophytes KCTC 6085, T. mentagrophytes KCTC 6077, T. mentagrophytes KCTC 6316, Microsporum canis KCTC 6591, M. canis KCTC 6348 and M. canis KCTC 6349. The oil also had a strong detrimental effect on spore germination as well as concentration and time-dependent kinetic inhibition of M. canis KCTC 6591.     

Toxicity of zinc oxide (ZnO) nanoparticles on human bronchial epithelial cells (BEAS-2B) is accentuated by oxidative stress

Although several studies reported that cytotoxic effects of various nanoparticles are partially due to induction of oxidative stress, it is unclear how oxidative state of the cell per se could influence its sensitivity to cytotoxic nanoparticles. This is of clinical significance because certain pathological conditions such as inflammation is associated with elevated oxidative stress and this may alter sensitivity of cells and tissues to cytotoxic nanoparticles. Hence, this study investigated how initial exposure of BEAS-2B human bronchial epithelial cells to oxidative stress influences subsequent response to cytotoxic challenge with zinc oxide (ZnO) nanoparticles (≈10 nm). Oxidative stress was induced by exposing BEAS-2B cells to 5 and 10 μM of H₂O₂ for 45 min in PBS (with Ca²⁺). Subsequently, the H₂O₂ solutions were washed off and the cells were exposed to varying concentrations (5–25 μg/ml) of ZnO nanoparticles in culture media for 24 h, followed by cell viability assessment with the WST-8 assay. The results demonstrated that initial transient exposure of cells to oxidative stress accentuated cytotoxicity of ZnO nanoparticles. In the negative control unexposed to H₂O₂, >99% of cells remained viable up to a ZnO nanoparticle concentration of 10 μg/ml, but displayed a steep decrease in viability above 10 μg/ml ZnO. By contrast, cells that were initially exposed to 5 and 10 μM of H₂O₂, displayed a sharp drop in viability even at concentrations below 10 μg/ml ZnO. At 10 μg/ml ZnO, cells initially exposed to 10 μM H₂O₂ displayed a viability of 40.6 ± 2.0%, which is significantly lower than the corresponding values of 72.8 ± 2.0% and 99.9 ± 1.1% obtained for initial exposure to 5 μM H₂O₂ and the negative control, respectively. Hence, initial exposure of BEAS-2B cells to oxidative stress sensitized their subsequent response to cytotoxic challenge with ZnO nanoparticles.     

Multivalent dendrimeric and monomeric adenosine agonists attenuate cell death in HL-1 mouse cardiomyocytes expressing the A3 receptor

Multivalent dendrimeric conjugates of GPCR ligands may have increased potency or selectivity in comparison to monomeric ligands, a phenomenon that was tested in a model of cytoprotection in mouse HL-1 cardiomyocytes. Quantitative RT-PCR indicated high expression levels of endogenous A₁ and A_2A adenosine receptors (ARs), but not of A_2B and A₃ARs. Activation of the heterologously expressed human A₃AR in HL-1 cells by AR agonists significantly attenuated cell damage following 4 h exposure to H₂O₂ (750 μM) but not in untransfected cells. The A₃ agonist IB-MECA (EC₅₀ 3.8 μM) and the non-selective agonist NECA (EC₅₀ 3.9 μM) protected A₃ AR-transfected cells against H₂O₂ in a concentration-dependent manner, as determined by lactate dehydrogenase release. A generation 5.5 PAMAM (polyamidoamine) dendrimeric conjugate of a N⁶-chain-functionalized adenosine agonist was synthesized and its mass indicated an average of 60 amide-linked nucleoside moieties out of 256 theoretical attachment sites. It non-selectively activated the A₃AR to inhibit forskolin-stimulated cAMP formation (IC₅₀ 66 nM) and, similarly, protected A₃-transfected HL-1 cells from apoptosis-inducing H₂O₂ with greater potency (IC₅₀ 35 nM) than monomeric nucleosides. Thus, a PAMAM conjugate retained AR binding affinity and displayed greatly enhanced cardioprotective potency.     

The antioxidant and cytoprotective activity of Ocimum gratissimum extracts against hydrogen peroxide-induced toxicity in human HepG2 cells

Ocimum gratissimum is used as a traditional folk medicine in many countries. The objective of this study was to evaluate the antioxidant activities of an aqueous O. gratissimum extract (OGE) and to evaluate its cytoprotective activity against hydrogen peroxide-induced toxicity in human HepG2 cells. The results revealed that the total phenolic content of the OGE reached 20%. In the 2,2-diphenyl-1-picrylhydrazyl (DPPH) assay, the OGE reduced up to 80% of the free radicals at a plateau concentration of 66.7 μg/mL. This indicates that OGE contains considerable free radical scavenging activity. In a dose-dependent manner, OGE pretreatment counteracted the decrease in cell viability in H₂O₂-treated HepG2 cells (p < 0.05), and at a concentration of 20–80 μg/mL, it effectively reduced thiobarbituric acid reactive substance (TBARS) formation. These findings indicated that the aqueous extract of O. gratissimum has an antioxidant capacity and protective effect on oxidative stress in HepG2 cells. This makes OGE a promising therapeutic agent in liver diseases.