Intraocular pressure-lowering activity of phenolic antioxidants in normotensive rabbits.
OBJECTIVE
The purpose of this study was to determine the intraocular pressure (IOP)-lowering activity of phenolic antioxidants injected intravenously into normotensive rabbits. Antioxidants belonging to the following classes were tested: cinnamic acids; flavonols; flavanols; anthocyanidins; isoflavones; and tannic acid.


METHODS
Test compounds were dissolved in either water or oil/saline as vehicle and injected intravenously into normotensive rabbits. IOP was monitored hourly after injection and expressed as a percent relative to preinjection values. Controls were conducted using vehicle alone. IOP from each eye was averaged to provide one value per rabbit. Dose-response data beginning at 0.01 mg-2 mg doses were collected for compounds shown to be active at 1 mg.


RESULTS
Epigallocatechin, epigallocatechin gallate and myricetin lowered IOP below control levels at doses of 1 mg. Tannic acid was the most active, lowering IOP more than 30% at doses of 200 microg.


CONCLUSIONS
Only phenolic antioxidants containing a pyrogallol B-ring system and nonaromatic C-ring (epigallocatechin, epigallocatechin gallate and myricetin) or possible galloyl glucosides as found in tannic acid were active in lowering IOP, with tannic acid being the most active. Other antioxidants were not active in this system suggesting a more specific structural requirement for interacting with appropriate ocular systems. The protein or proteoglycan-binding properties of these molecules may also be important in this activity.
Hodges
L C
LC
Agnes Scott College Department of Chemistry GA 30030, Decatur, USA. lhodges@agnesscott.edu
Kearse
C E
CE
Green
K
K
D000818:Animals; D000975:Antioxidants / Q000494:pharmacology*; D004305:Dose-Response Relationship, Drug; D005419:Flavonoids; D006863:Hydrogen-Ion Concentration; D007429:Intraocular Pressure / Q000187:drug effects*; D019999:Pharmaceutical Solutions / Q000494:pharmacology; D010636:Phenols / Q000494:pharmacology*; D011108:Polymers / Q000494:pharmacology*; D059808:Polyphenols; D011817:Rabbits; D012995:Solubility; D013997:Time Factors
D000975:Antioxidants; D005419:Flavonoids; D019999:Pharmaceutical Solutions; D010636:Phenols; D011108:Polymers; D059808:Polyphenols