THE CUTICLE OF THE CACTUS CEREUS-PERUVIANUS AS A SOURCE OF A HOMO-ALPHA-D-GALACTURONAN

The waxy pecto-cellulosic cuticle of cladodes of the columnar cactus C ereus peruvianus (19% of the whole phytobiomass; dry wt) is a source o f an alpha-D-polygalacturonic or pectic acid (35-40% yield, on a dry w t based on the wax-free pectocellulose layer). Warm EDTA/oxalate or ro om temperature strong acid/alkali cycles are efficient for pectic acid extraction, since divalent cation (mainly Ca2+) is a barrier to be re moved within the native and compact architecture of the cuticle. Despi te some molecular dispersion arising from the application of strong mi neral acid in the first extraction step, the pectic material appears t o be quite homogeneous and, on acid or enzymatic analyses, was shown t o contain only D-galacturonic acid as its monomer. Cereus cuticle pect ate (sodium salt) tends to gel above a concentration of 1%, a useful p roperty that can be more easily obtained by the inclusion of sucrose, light addition of calcium salt, and/or mild acidification.