Abstract
Purpose :
Non-UV light stimulated CXL strategies are under study by several groups. We demonstrated that Acaí (Euterpe oleracea) promotes stronger corneal stiffness than traditional riboflavin activated protocols. Other polyphenols rich plants may be advantageous candidates as they does not tint the stroma and may be of faster response under smaller concentrations. This study determined the best solvent to extract proanthocyanidins (PA) from Stryphnodendron adstringens bark, and measure its crosslinking effect in the porcine corneal stroma by DSC.
Methods :
Steam bark of S. adstringens was grinded and subjected to extraction by either acetone/water mixture (2:1); consecutive extractions with hexane followed by ethyl acetate, butanol or water (on ultrasound); hot extraction with methanol under reflux or hot extraction with water under reflux. All samples were analyzed by the HCl/butanol method to determine PA content. Two freshly obtained porcine eyes had a 8mm de-epithelialized corneal button excised, divided in 4 slices, immersed for 2 hs in a 4% aqueous solution of each extract (plus 1 control slice) and analyzed by DSC. Four whole eyes had its corneas de-epithelialized, face down immersed for 2 hs in 0 (control), 1, 2 and 4% butanolic extract concentration, sliced in 3 pieces each and further evaluated by DSC.
Results :
Butanolic extraction presented a higher PA percentage, lower concentration of pigments and higher denaturation temperature (Td) of the cornea compared to other extracts as shown in table 1. Td values for the control eye, 1, 2 or 4% of the butanolic extract were respectively 67.7±1.9 oC; 70.3±1.0 oC; 75.4±4.6 oC and 90.2±4.9 oC.
Conclusions :
This study showed that the butanolic extract of S. adstringens contains a PA concentration that promotes an increase in Td of the porcine cornea. Td increase was directly related to the concentration of the butanolic extract.
This abstract was presented at the 2019 ARVO Annual Meeting, held in Vancouver, Canada, April 28 - May 2, 2019.