Aldose Reductase

Aldose reductase is a human enzyme that converts aldehydes into alcohols by the addition of hydrogen (H) to to a double bonded oxygen site (C=0 becomes C-OH).

Aldose reductase reduces the aldehyde portion of glucose creating the sugar alcohol sorbitol.

Glucose Aldose reductase Sorbitol
Glucose-UP.gif —-> sorbitol-UP.gif

Effects on Norepinephrine Metabolism

The normal pathway in humans for norepinephrine (NE) is deamination by monoamine oxidase (MAO), forming an aldehyde which is then either metabolized to 3,4-dihydroxy-mandelic acid (DHMA) by aldehyde dehydrogenase or is converted to 3,4-dihydroxyphenylglycol (DHPG) by or aldose reductase.

The same metabolic pathways exists in rats. In vivo tests performed on rats given aldose reductase inhibitors caused a sharp increase in the formation of DHMA and a decrease in the formation of DHPG.[6] Because human metabolism of NE follows the same pathway it can be concluded that inhibition of aldose reductase in humans should produce an increase in DHMA and a decrease in DHPG.


Potent Inhibitors Strength Dosage Verified in Man
Cuminaldehyde IC50 0.00085 mg/mL[1]1 ? ?
Cinnamaldehyde IC50 0.003 mg/mL[3]2 ? ?
Myricitrin [4] ? ? ?
Quercetin IC50 2 mM[2] ? ?
Quercitrin [4] ? ? ?
Rutin IC50 5 mM[2] ? ?
Moderate Inhibitors Strength Dosage Verified in Man
Black pepper water extract 0.22 mg/ml[5] ? ?
Orange fruit water extract 0.25 mg/ml[5] ? ?

1. Cuminaldehyde: Aldose Reductase and alpha-Glucosidase Inhibitor Derived from Cuminum cyminum L. Seeds.
Lee HS. PubMed PMID: 15796577
2. Purification and characterization of human-brain aldose reductase.
Wermuth B, B├╝rgisser H, Bohren K, von Wartburg JP. PubMed PMID: 6814912
3. Inhibitory activity of Cinnamomum cassia bark-derived component against rat lens aldose reductase.
Lee HS. PubMed PMID: 12553890
4. Flavonoids as inhibitors of lens aldose reductase.
Varma SD, Mikuni I, Kinoshita JH. PubMed PMID: 1145193
5. Dietary sources of aldose reductase inhibitors: prospects for alleviating diabetic complications.
Saraswat M, Muthenna P, Suryanarayana P, Petrash JM, Reddy GB. PubMed PMID: 19114390
6. Effects of aldehyde/aldose reductase inhibition on neuronal metabolism of norepinephrine.
Kawamura M, Kopin IJ, Kador PF, Sato S, Tjurmina O, Eisenhofer G. PubMed PMID: 9406118
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