DSC characterization of enzymatic digestion of corneas treated with plant extracts rich in polyphenols

Keratoconus is a progressive disease that affects patients' quality of life by producing corneal irregular astigmatism and low vision as the cornea becomes thinner and presents a conical protrusion. Inducing cross-linking in keratoconic corneal stroma is the current preventive intervention that effectively blocks the progression of this ectasia. As a result of this process, there is an increase in biomechanical strength and resistance of the cornea. In this context, two plant extracts rich in polyphenols (Euterpe oleracea and Stryphnodendron adstringens) have been tested in this study to compact and stiffen the tissue, and its effect was evaluated by enzymatic digestion of porcine corneas. Thermal analysis by DSC was employed to verify the corneal resistance to degradation induced by the plant extracts. The values of temperature and enthalpy of denaturation at the initial time were: 65.6 +/- 0.3 degrees C/3.8 +/- 0.3 J g(-1); 79.4 +/- 0.5 degrees C/5.5 +/- 0.4 J g(-1); and 93.1 +/- 1.2 degrees C/8.0 +/- 0.6 J g(-1), respectively, for the control, E. oleracea, and S. adstringens groups. After 24 h of collagenase digestion, these values were: 60.1 +/- 0.8 degrees C/1.3 +/- 0.1 J g(-1); 78.1 +/- 1.0 degrees C/5.6 +/- 0.6 J g(-1); and 93.2 +/- 0.6 degrees C/8.1 +/- 0.06 J g(-1), respectively. These results show that there was no decrease in temperature and enthalpy of denaturation (p < 0.01) in corneas of the groups treated with the E. oleracea or S. adstringens extracts. However, in the control group, the temperature and the enthalpy decreased by approximately 8% and 65%, respectively. Therefore, this work demonstrated for the first time that plant extracts rich in polyphenols were efficient in decreasing the digestion and increasing the denaturation temperature of corneas.