Syzygium aromaticum Reduces Diabetes-induced Glucotoxicity via the NRF2/Glo1 Pathway

Syzygium aromaticum essential oil and its major constituents: Assessment of activity against Candida spp. and toxicity

Syzigium aromaticum essential oil (EO), eugenol, and β-caryophyllene were evaluated regarding antifungal, antibiofilm, and in vitro toxicity. Additionally, in vivo toxicity of EO was observed. Anti-Candida activity was assessed through broth microdilution assay for all compounds. Time-kill assay (0, 1, 10, 30 min, 1, 2, and 4 h) was used to determine the influence of EO and eugenol on Candida Growth kinetics. Thereafter, both compounds were evaluated regarding their capacity to act on a biofilm formation and on mature biofilm, based on CFU/ml/g of dry weight. Cell Titer Blue Viability Assay was used for in vitro cytotoxicity, using oral epithelial cells (TR146) and human monocytes (THP-1). Lastly, Galleria mellonella model defined the EO in vivo acute toxicity. All compounds, except β-cariofilene (MIC > 8000 μg/ml), presented antifungal activity against Candida strains (MIC 500-1000 μg/ml). The growth kinetics of Candida was affected by the EO (5xMIC 30 min onward; 10xMIC 10 min onward) and eugenol (5xMIC 10 min onward; 10xMIC 1 min onward). Fungal viability was also affected by 5xMIC and 10xMIC of both compounds during biofilm formation and upon mature biofilms. LD50 was defined for TR146 and THP1 cells at, respectively, 59.37 and 79.54 μg/ml for the EO and 55.35 and 84.16 μg/ml for eugenol. No sign of toxicity was seen in vivo up to 10mg/ml (20 x MIC) for the EO. S. aromaticum and eugenol presented antifungal and antibiofilm activity, with action on cell growth kinetics. In vivo acute toxicity showed a safe parameter for the EO up to 10 mg/ml.

Isolation of secondary metabolites from Syzygium aromaticum (L.) Merr. & L.M.Perry. (cloves), and evaluation of their biological activities

Phytochemical investigation of dried flower buds of Syzygium aromaticum (L.) Merr. & L.M.Perry. (clove) led to the isolation and identification of fourteen known compounds, oleanolic acid (1), betulinic acid (2), para methyl benzoic acid (3), sabrinic acid (4) eucalyptolic acid (5), nigricin (6), 3-O-trans-para-coumaroylmaslinic acid (7), methyl maslinate (8), maslinic acid (9), 3, 4, 5-trimethoxy-3',4'-O,O-methylideneflavellagic acid (10), lantanone (11) 3,4,3'-trimethoxyellagic acid (12), 11-oxo-oleanolic acid (13), and β-sitosterol-3-O-β-D-glucopyranoside (14). Their structures were identified by ¹H NMR, ¹³C NMR, Mass spectroscopic techniques, and comparison with the literature data. Compounds 3, and 7-9 showed a strong mortality against root knot nematode, Meloidogyne incognita at 0.125% concentration after 72 hours (88-92% inhibition). Compound 4 showed a good anti-glycation activity with IC₅₀ = 142.0 ± 1.8 µM when compared with standard, i.e. rutin (IC₅₀ = 54.59 ± 2.20 µM). Compound 10 showed a comparable urease inhibitory activity (IC₅₀ = 26.1 ± 0.19 µM) with the positive control thiourea (IC₅₀ = 24.5 ± 0.34 µM).

Cell-Based Antioxidant Properties and Synergistic Effects of Natural Plant and Algal Extracts Pre and Post Intestinal Barrier Transport

In this work, both direct and indirect cell-based antioxidant profiles were established for 27 plant extracts and 1 algal extract. To evaluate the direct antioxidant effects, fluorescent AOP1 cell assay was utilized, which measures the ability of different samples to neutralize intracellular free radicals produced by a cell-based photo-induction process. As the intestinal barrier is the first cell line crossed by the product, dose response curves obtained from Caco-2 cells were used to establish EC50 values for 26 out of the 28 natural extracts. Among them, 11 extracts from Vitis, Hamamelis, Syzygium, Helichrysum, Ilex and Ribes genera showed remarkable EC50s in the range of 10 µg/mL. In addition to this, a synergistic effect was found when combinations of the most potent extracts (S. aromaticum, H. italicum, H. virginiana, V. vinifera) were utilized compared to extracts alone. Indirect antioxidant activities (i.e., the ability of cells to trigger antioxidant defenses) were studied using the ARE/Nrf2 luminescence reporter-gene assay in HepG2 cells, as liver is the first organ crossed by an edible ingredient once it enters in the bloodstream. Twelve extracts were subjected to an intestinal epithelial barrier passage in order to partially mimic intestinal absorption and show whether basolateral compartments could maintain direct or indirect antioxidant properties. Using postepithelial barrier samples and HepG2 cells as a target model, we demonstrate that indirect antioxidant activities are maintained for three extracts, S. aromaticum, H. virginiana and H. italicum. Our experimental work also confirms the synergistic effects of combinations of post-intestinal barrier compartments issued from apical treatment with these three extracts. By combining cell-based assays together with an intestinal absorption process, this study demonstrates the power of cell systems to address the issue of antioxidant effects in humans.

Diabetic nephropathy induced by methylglyoxal: gallic acid regulates kidney microRNAs and glyoxalase1-Nrf2 in male mice

BACKGROUND

Methylglyoxal (MG) has been reported to be a toxic by-product of glycolysis and intracellular stressor compound. This study investigated the effects of gallic acid (GA) against diabetic nephropathy (DN) induced by MG in male mice.

METHODS

DN was induced by methylglyoxal (600 mg/kg/day, p.o.) treated for 28 consecutive days. The animals received GA (30 mg/kg/day, p.o.) and metformin (MT) (150 mg/kg/day, p.o.) for 7 consecutive days after diabetes induction. Biochemical assays, antioxidant evaluation, microRNAs associated with fibrosis, endoplasmic reticulum stress, and histopathological analysis were examined.

RESULTS

MG increased malondialdehyde, albuminuria, Nrf2, miR-192 and miR-204 expression in diabetic groups and GA decreased them. Superoxide dismutase, catalase, glyoxalase1, and miR-29a expression decreased in diabetic groups and increased in treatment with GA.

CONCLUSION

Our results revealed that GA has improved DN induced by MG via amelioration of biochemical indices, histopathological aspects, oxidative stress and microRNAs associated with endoplasmic reticulum stress and fibrosis.