Inhibitory effects of compounds isolated from Lepechinia meyenii on tyrosinase.

To contribute enzymatic browning inhibitors to the food industry and also extend knowledge about the phytochemical profile of the anti-tyrosinase plant Lepechinia meyenii, its ethanol extract was subjected to bioguided fractionation. Three hydroxycinnamic acids, p-coumaric acid (1), caffeic acid (2) and rosmarinic acid (3), were isolated as mainly responsible for its activity. Compounds 1, 2 and 3 showed themselves highly effective for inhibiting tyrosinase with IC50 values of 0.30, 1.50 and 4.14 µM, respectively, for monophenolase activity and 0.62, 2.30 and 8.59 µM, respectively for diphenolase activity. This is the first report describing the isolation of the compounds causing the tyrosinase inhibitory activity of L. meyenii extract. The inhibitory kinetics of 1-3 using both L-tyrosine and L-DOPA as substrates was investigated and the results obtained were discussed at molecular level by docking analysis. The resulting compounds 1-3 and a phenolic-enriched fraction of the extract, 2.9-fold more active than the starting material, may be suitable as non-toxic and inexpensive alternatives for the control of deleterious enzymatic darkening.

Effects of isopentyl ferulate on oxidative stress biomarkers and a possible GABAergic anxiolytic-like trait in Swiss mice.

This study aimed to evaluate the anxiolytic-like effect and the possible neuronal mechanism of action of isopentyl ferulate (IF). For this purpose, we used the marble burying test in Swiss albino mice. The biomarkers involved in oxidative stress were measured in the hippocampus homogenate of the test animals. In addition, the toxicity and antioxidant capacities were tested in Artemia salina and rat erythrocytes, respectively. The results suggest that, an acute administration of the IF at doses of 25, 50, 75 and 150 mg/kg (intraperitoneal, i.p.) significantly (p < 0.05) reduced the marble burying behavior of the animals as compared to the vehicle group, which demonstrates a calming effect of this chemical. It was observed that, the pre-treatment with flumazenil (2.5 mg/kg, i.p.), an antagonist of the gamma-amino butyrinc acid (GABAA) receptor, significantly reversed the marble burying behavioral activity in the animals treated with the IF 150 mg/kg dose. Moreover, the reduction in nitrite content and lipid peroxidation levels, while an increased in the reduced glutathione (GSH), glutathione peroxidase (GPx), superoxide dismutase (SOD) and catalase (CAT) activities were also observed their hippocampus. Although, IF (2.36-14.16 mM) did not show toxicity in A. salina but exhibited a prominent antioxidant capacity in hydrogen peroxide-induced oxidative damage in rat erythrocytes. In conclusion, IF exhibited an anxiety-like effect in mice along with a potent antioxidant capacity, and we suppose it may have neuroprotective effects possibly via GABAergic transmission pathway.

In vitro genotoxicity assessment of caffeic, cinnamic and ferulic acids.

Phenols are a large and diverse class of compounds, many of which occur naturally in a variety of food plants; they exhibit a wide range of biological effects, including antibacterial, anti-inflammatory, antiallergic, hepatoprotective, antithrombotic, antiviral, anticarcinogenic, and vasodilatory actions. We examined the genotoxic and clastogenic potential of three phenolic compounds: caffeic, cinnamic and ferulic acids, using the comet and micronucleus assays in vitro. Drug-metabolizing rat hepatoma tissue cells (HTCs) were used. Three different concentrations (50, 500 and 1500 µM) of these phenolic acids were tested on the HTCs for 24 h. The caffeic, cinnamic and ferulic acids were not genotoxic by the comet assay (P > 0.05). However, the micronucleus test showed an increase in the frequency of micronucleated cells for the three compounds, indicating that these substances have clastogenic effects in HTC.