Recovery of oral glucose tolerance by wistar rats after treatment with Coreopsis tinctoria infusion

Abstract

Infusions of Coreopsis tinctoria flowering tops have traditionally been used in Portugal to control hyperglycaemia but no pharmacological or toxicological studies have been reported until now. The chalcones marein and okanin were isolated from the aqueous extract, together with the 2S-3',4',7,8-tetrahydroxyflavanone. The content of marein in extracts was determined by HPLC-UV and the radical scavenging capacity evaluated by the DPPH method (EC(50) = 21 microg/mL). Glucose intolerance was induced by a single intraperitoneal injection of streptozotocin in saline (40 mg/Kg). After three weeks of oral treatment with C. tinctoria extract (500 mg/Kg/day) the animals were no longer glucose-intolerant (p > 0.05). Additionally, this oral treatment caused no hepatotoxicity in the rats, as determined by blood alanine and aspartate transaminases. A single administration of extract had no effect on oral glucose tolerance in normal Wistar rats. The extract also had no effect on insulin secretion by MIN6 cells. In conclusion, C. tinctoria infusion is able to abolish the streptozotocin-induced glucose-intolerance in rats after three weeks of oral treatment by a mechanism other than induction of insulin secretion. The recovery of beta-pancreatic function mediated by an antioxidant mechanism is a possibility that deserves further investigation.

The flavonoid-rich fraction of Coreopsis tinctoria promotes glucose tolerance regain through pancreatic function recovery in streptozotocin-induced glucose-intolerant rats

“…were acquired from local herbal shop. Plant identity was confirmed and infusion prepared as previously described (Dias et al, 2010). The infusion was then exhaustively extracted by partition with ethyl acetate to afford the AcOEt fraction (5.3% w/w dry plant material).…”

“…Chlorogenic acid (2) and Quercetagitin-7-O-glucoside (7) were purchased from Sigma (Spain). Okanin (12) and Flavanokanin (5) were isolated from Coreopsis tinctoria and identified by NMR (Dias et al, 2010). Standards stock solutions (1 mg/ml) were prepared with acetonitrile (MS grade from Merck) and solutions were further diluted for analysis.…”

“…Additionally, in Portugal, 2 cups per day of an infusion of Coreopsis tinctoria flowering tops, known as "Estrelas-do-Egipto", has been traditionally used to control diabetes (D'Oliveira Feijão, 1973). Based on this ethnopharmacological use we studied this plant's flowers infusion, and showed an insulinotropic-independent blood glucose lowering effect on glucose-intolerant Wistar rats, after a 3-week daily oral treatment (Dias et al, 2010). In order to identify the active principles we studied the chemical composition and pharmacological activity of the flavonoid-rich ethyl acetate fraction of the bioactive Coreopsis tinctoria infusion, which we now report.…”

“…Treatment of streptozotocininduced diabetic rats with antioxidant ␣-lipoic acid significantly suppressed mitochondrion-dependent apoptosis in cardiac tissue (Bojunga et al, 2004). For comparative purposes with Coreopsis tinctoria flavonoids' antihyperglycaemic effect, which was proposed to be by antioxidant-mediated recovery of ␤-cell function (Dias et al, 2010), the effect of a standard antioxidant (Trolox) on oral glucose tolerance was also evaluated.…”

Metabolic and biological prospecting of Coreopsis tinctoria

“…Despite this, C. tinctoria fl owering tops constitute a poorly studied matrix. Only recently few studies have correlated its chemical composition with the promotion of glucose tolerance (Dias et al, 2010a;Dias et al, 2010b). So far, C. tinctoria fl owering tops have been reported to contain fl avonoids, namely chalcones (Shimokoriyama, 1957), aurones (Shimokoriyama, 1957), anthocyanins (Shimokoriyama, 1957), fl avanones (Shimokoriyama, 1957) and fl avonols (Dias et al, 2010a), as well as phenylpropanoids (Dias et al, 2010a, Shimokoriyama, 1957, Reichling & Thron, 1989.…”