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Legend: The results represent the medium ± standard deviation of 8-10 determinations per treatment, estimated of serum levels of fructosamine. ANOVA was determined and the letters indicate that there was significant difference of Tukey-Kramer test, adopting p<0,05.
The diuretic effect of artichoke helps the urea and toxic substances eliminate, developing a depurative action. One of the antioxidant compounds present in the artichoke is the vitamin E, which in the human body is soluble in fat and has an effect on the oxidative stress involved in aging and complications as diabetes (Lactantius 2002). The fact that the artichoke is rich in dietetic fibres gives the artichoke the properti to regulate intestinal activity, contributing to the control of blood glucose and cholesterol levels [Ceccarelli,, Curadi & Picciarelli, 2010].
According to [Gebhardt, 1997], the extracts with a higher content of phenolic derivatives present a higher protection of the liver, as well as antioxidant activities (they can limit the oxidative stress and restore the endothelial functions). Probability, the caffeine derivatives have a role in therapeutic activities of the artichoke when administered in vitro, but not in isolation. The leaf artichoke extract is capable not only to increase the bile flow, by reducing the cholesterol levels, but also to reestablish this flow when it is inhibited. These effects are performed by luteolin and to a lesser extent by luteolin-7-o-glucoside, while the chlorogenic acid and 1,5-dicaffeoylquinic are almost inefficient.
The antioxidant activity of flavonoids is obviously linked to its structure and can be determined by the following factors: The reactivity as donor agent of hidrogenom or electrons, stability of the formed flavonyl radical, reactivity against others antioxidants, capacity to chelate transitions metals, solubility and interaction with membranes. At the same time, its capacity to kidnap free radicals is directly linked to its oxidation potential and to the species to be kidnapped, and the lower oxidation potential of the flavonoids, higher is its capacity as kidnapper of free radicals [Barreiros, David & Juceni, 2006].
Quercetin actuates normalizing the plasmatic glucose levels, increasing the content of hepatic glycogen and inducing the enzymes hepatic glucokinase and hexokinase [Vessal, Hemmati & Vasei, 2003]. The flavonoid naringenin is known to block the activity of the PI-3K in adipocytes and thus inhibiting the captivation of glucose. Another 14 flavonoids were investigated as possible inhibitory action on PI-3K, such as quercetin, luteolin, myricetin, apigenin and diosmetin which showed any type of inhibition on activity of the PI-3K [Agullo, Gamet-Payrastre, Manenti,Viala, Remesy, Chap & Payrastre. 1997].
Some authors showed that the quercetin has several effects on glucose metabolism when administered orally to diabetic animals in a subchronic treatment. Effects such as the decrease of glycemics levels, increase of the hepatic hexokinase and glucokinase activity and normalization of the glucose tolerance curve, in addition to an increase in the number of the pancreatic islets. The authors linked these effects to the antioxidant potential that quercetin has and as this consequence, it would be regenerating pancreatic cells and increasing insulin secretion, therefore, these actions of the glucose metabolism would be due to the increased insulin secretion [Vessal, Hemmati & Vasei, 2003].
According to [Salles, da Silva, Taniguthi, Ferreira, da Rocha, Vilegas., Dias, Pennacchi, Duarte, Rodrigues, Brigagão & Paula. 2020] the dyslipidemic observed in diabetic animals can be attributed to the hyperglycemic shown by them. The hypercholesterolemia due to type 2 DM has been linked to the increase of the atherogenic lipoproteins such as, low density lipoprotein (LDL) and very low density lipoprotein (VLDL).
However, it has been reported that in type 1 DM, an increase in the serum concentration of HDL cholesterol may be linked to high or normal concentrations of the other lipoproteins [Kahri, Groop, Viberti, Elliot & Taskinen. 1993]. In this case, despite the high levels of HDL cholesterol, there is no reduction in cardiac risk in these individuals, since changes in the size, composition and structure of HDL may be present, compromising their functionality and negatively interfering with their antiatherogenic properties [Sviridov, Kingwell, Hoang, Dart & Nestel. 2003].
In our studies, an increase in the concentration of total cholesterol and triglycerides in the serum of diabetic animals when compared to non-diabetic animals (Table 1), compatible with the metabolics alterations observed in diabetes mellitus.
Diabetic animals treated with the artichoke extracts showed serum levels of total cholesterol and triglycerides significantly lower than non-treated animals (Table 1).
Table 1 - Evaluation of lipid profile in serum of Wistar rats