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Food Process Engineering in a Changing World - 11th International ...

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RESULTS AND DISCUSSION<br />

Km value for -amylase was found to be 1.8% starch with a Vmax value of 6.8 μM m<strong>in</strong> -1 . The results<br />

<strong>in</strong>dicate that maqui leaf crude extracts act as mixed-type <strong>in</strong>hibitors, b<strong>in</strong>d<strong>in</strong>g to either -amylase (E)<br />

or enzyme-substrate (ES) complex, result<strong>in</strong>g <strong>in</strong> a decrease <strong>in</strong> the apparent aff<strong>in</strong>ity of -amylase for<br />

starch (<strong>in</strong>crease Km) and a decrease <strong>in</strong> the apparent Vmax. A similar type of Acarbose <strong>in</strong>hibition and<br />

for the two Acarbose analogues for porc<strong>in</strong>e pancreatic -amylases was reported by Yoon and<br />

Robyt [5]. Similar behavior appears reported <strong>in</strong> literature for f<strong>in</strong>ger millet seed coat phenolics,<br />

which behave as non-competitive <strong>in</strong>hibitors on pancreatic -amylase, be<strong>in</strong>g Km value for this<br />

enzyme about 1% starch [3].<br />

The v of the hydrolysis reactions catalyzed by -glucosidase was measured at various substrate<br />

concentrations [S] (2-5 – 15-0 mM pNPG) <strong>in</strong> the absence and presence of several maqui leaf crude<br />

extract concentrations [I] (0.05 – 5-0 ppm). The Km for -glucosidase was found to be 3.5 mM<br />

starch with a Vmax value of 0.25 mM m<strong>in</strong> -1 . The results of this study <strong>in</strong>dicate that b<strong>in</strong>d<strong>in</strong>g of<br />

phenolic compounds to enzyme affected the velocity of -glucosidase reaction rate, proportionally<br />

to the concentration of the phenolic compounds <strong>in</strong> the reaction mixture, not modify<strong>in</strong>g Km value.<br />

Thus, a non-competitive <strong>in</strong>hibition by maqui leaf crude extracts upon -glucosidase-catalyzed<br />

pNPG hydrolysis was found <strong>in</strong> this study. Reversible non-competitive <strong>in</strong>hibition of -glucosidase is<br />

reported <strong>in</strong> literature for aqueous extracts from the gall of Rhus ch<strong>in</strong>ensis [2]. Alpha-glucosidase<br />

<strong>in</strong>hibition by several flavonoids has been reported as mixed-type and almost non-competitive [4].<br />

CONCLUSION<br />

Furthermore, the evaluation of digestive enzyme <strong>in</strong>hibition <strong>in</strong> the extract represents a prelim<strong>in</strong>ary<br />

approach to the potential biological properties of maqui leaves, which are used <strong>in</strong> traditional<br />

medic<strong>in</strong>e.<br />

REFERENCES<br />

[1] Gao H., Huang Y.N., Gao B., Xu P.Y, Inagaki C.; Kawabata J. 2008. -glucosidase <strong>in</strong>hibitory effect by the<br />

flower buds of Tussilago farfara L. <strong>Food</strong> Chemistry, 106, 1195-1201.<br />

[2] Shim Y.-J., Doo H.-K., Ahn S.-Y., Kim Y.-S., Seong J.-K., Park I.-S., M<strong>in</strong> B.-H. 2003 Inhibitory effect of<br />

aqueous extract from the gall of Rhus ch<strong>in</strong>ensis on alpha-glucosidase activity and postprandial blood<br />

glucose. Journal of Ethnopharmacology, 85, 283-287.<br />

[3] Shobana, S.; Sreerama, Y.N., Malleshi, N.G. 2009. Composition and enzyme <strong>in</strong>hibitory properties of<br />

f<strong>in</strong>ger millet (Eleus<strong>in</strong>e coracana L.) seed coat phenolics: mode of <strong>in</strong>hibition of a-glucosidase and<br />

pancreatic amylase. <strong>Food</strong> Chemistry 115, 1268–1273.<br />

[4] Tadera K.; M<strong>in</strong>ami Y.; Takamatsu K.; Matsuoka T. 2006.Inhibition of -glucosidase and -amylase by<br />

flavonoids. Journal of Nutritional Science and Vitam<strong>in</strong>ology. 52, 149-153.<br />

[5] Yoon S.-H.; Robyt J.F. 2003Study of the <strong>in</strong>hibition of four alpha amylases by acarbose and its 4IV-amaltohexaosyl<br />

and 4IV-a-maltododecaosyl analogues. Carbohydrate Research, 338, 1969-1980.<br />

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