Hypoglycemic activity of a novel anthocyanin-rich formulation from lowbush blueberry, Vaccinium angustifolium Aiton - PubMed (original) (raw)

Hypoglycemic activity of a novel anthocyanin-rich formulation from lowbush blueberry, Vaccinium angustifolium Aiton

Mary H Grace et al. Phytomedicine. 2009 May.

Abstract

Blueberry fruits are known as a rich source of anthocyanin components. In this study we demonstrate that anthocyanins from blueberry have the potency to alleviate symptoms of hyperglycemia in diabetic C57b1/6J mice. The anti-diabetic activity of different anthocyanin-related extracts was evaluated using the pharmaceutically acceptable self-microemulsifying drug delivery system: Labrasol. Treatment by gavage (500 mg/kg body wt) with a phenolic-rich extract and an anthocyanin-enriched fraction formulated with Labrasol lowered elevated blood glucose levels by 33 and 51%, respectively. The hypoglycemic activities of these formulae were comparable to that of the known anti-diabetic drug metformin (27% at 300 mg/kg). The extracts were not significantly hypoglycemic when administered without Labrasol, demonstrating its bio-enhancing effect, most likely due to increasing the bioavailability of the administered preparations. The phenolic-rich extract contained 287.0+/-9.7 mg/g anthocyanins, while the anthocyanin-enriched fraction contained 595+/-20.0 mg/g (cyanidin-3-glucoside equivalents), as measured by HPLC and pH differential analysis methods. The greater hypoglycemic activity of the anthocyanin-enriched fraction compared to the initial phenolic-rich extract suggested that the activity was due to the anthocyanin components. Treatment by gavage (300 mg/kg) with the pure anthocyanins, delphinidin-3-O-glucoside and malvidin-3-O-glucoside, formulated with Labrasol, showed that malvidin-3-O-glucoside was significantly hypoglycemic while delphinidin-3-O-glucoside was not.

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Figures

Figure 1

Figure 1

Flow chart showing extraction, clean-up and anthocyanin enrichment process from blueberry frozen fruits.

Figure 2

Figure 2

RP-HPLC-PDA chromatograms of blueberry phenolic-rich extract (A), and anthocyanin-enriched fraction (B) showing relative absorbance of 17 individual anthocyanins at 520nm. For peak identification, see Table 2.

Figure 3

Figure 3

Hypoglycemic effect of blueberry phenolic-rich and anthocyanin-enriched extracts relative to metformin in insulin resistant C57bl/6J mice. The animals were maintained on a high fat diet and food restricted 4 hours prior to treatment by gavage. The extracts and metformin were formulated with 66% Labrasol as the delivery vehicle. The anthocyanin-enriched extract was also used with only water as the vehicle and compared to water and the other treatments. *:p<0.05; **:p<0.01; ***:p<0.001 vs. 0 hr. c:p<0.05; cc:p<0.01;ccc:p<0.001vs vehicle

Figure 4

Figure 4

Hypoglycemic effect of delphinidin-3-glucoside (Dp 3-glc), malvidin-3-glucoside (Mv-3-glc) relative to blueberry anthocyanin-enriched extracts and metformin in insulin resistant C57bl/6J mice. The animals were maintained on a high fat diet and food restricted 4 hours prior to treatment by gavage. The extracts and metformin were formulated with 66% Labrasol as the delivery vehicle *:p<0.05; **:p<0.01; ***:p<0.001 vs. 0 hr.

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