Benedict’s TestScreening Tests for Certain

Inborn Errors of Metabolism

Benedict’s TestO Test for presence of reducing

sugars:

O Reducing monosaccharides:O glucose, fructose, glyceraldehyde and

galactose

O DisaccharidesO Lactose and maltose

Benedict’s TestO Benedict’s reagent can be used to

test for presence of glucose in urineO Indication of diabetes

O Heating a Benedict’s solution mixed with monosaccharides will produce a reddish-orange color

Benedict’s Reagent

Contains blue copper(II) sulfate (CuSO4)

reduced to copper(I) ions

(Cu+)

which are precipitated as red copper oxide which is

insoluble in water.

Benedict’s ReagentO Carbohydrates that contain aldehydes or a-

hydroxymethyl ketones can be oxidized by Cu(II)ions are classified as reducing sugars. They reduce the Cu(II) to Cu(I).

O

H + Cu2+

O

H + Cu2O(s)

R R

Results

Negative Blue

Green to Yellow +

Yellow to Brown ++

Brown to Orange +++

Orange to Red ++++

Reducing Substance

Clinical State

Drugs Ascorbic acid, chloral hydrate, tetracyclines, sulfonamides, chloramphenicol

Fructose Fructosemia, essential fructosuria, hereditary fructose intolerance

Galactose Galactosemia, classic and variant (galactokinase deficiency)

Glucose Diabetes mellitus, renal glycosuria, Fanconi’s Syndrome, Wilson’s Disease

Homogentisic acid Alkaptonuria

Lactose Lactase deficiency, lactose intolerance, newborn

Phenolic compound Phenylketonurias, tyrosinosis

Xylose Excessive fruit intake

Xylulose Pentosuria

Urinary Substances and Clinical Syndromes Associated with Reducing Substances

Methodology

Pour 5 ml of

Benedict’s Reagent

Heat to Boiling

Add 8 Drops of

Urine

Boil for 2 minutes/ Place in boiling

bath for 3 minutes

Results