Aglycone geniposidic acid, a naturally occurring crosslinking agent, and its application for the fixation of collagenous tissues

A natural compound, aglycone geniposidic acid (aGSA), originated from the fruits of Gardenia jasminoides ELLIS was used for the fixation of collagenous tissues. The presumed crosslinking reaction mechanism of collagenous tissues with aGSA was inferred by reacting aGSA with a bifunctional amine, 1,6-hexanediamine, using a series of ¹H NMR, FT-IR, and UV/Vis spectra analyses. aGSA reacted with 1,6-hexanediamine by a nucleophilic attack on the olefinic carbon atom at C-2 of deoxyloganin aglycone, followed by opening the dihydropyran ring to form heterocyclic amine compounds. It is inferred that aGSA may form intramolecular and intermolecular crosslinks with a heterocyclic structure within collagen fibers in tissues. The degrees of tissue fixation by aGSA at different pH values were investigated by examining the fixation indices and denaturation temperatures of test samples. It was found that the fixation indices and denaturation temperatures of test samples fixed at neutral or basic pH (pH 7.4 or pH 8.5) were significantly greater than at acidic pH (pH 4.0). The results obtained in this study may be used to elucidate the crosslinking mechanism and optimize the fixation process for developing bioprostheses fixed by aGSA.