Protein content and glucosinolates from Moringa oleifera Lam. – New insights into an auspicious commodity

Abstract

Moringa  oleifera  is  considered  to  be  one  of  the  most  valuable  and  beneficial crop tree species. The great nutritiousness is assigned to its  high  leaf  protein  content,  and  its  health-promoting  effect  to  the  anti-carcinogenic  properties  of  its  genuine  glucosinolates  and  their  degradation products.
From  a  plant  physiological  perception  protein  contents  of  30%  seem to be quite high. Accordingly, a reconsideration of these findings became necessary. The related inquiry unveils that also in the leaves  of  many  other  plant  species  such  high  protein  contents  are  reported, provided that they are quantified by Kjeldahl nitrogen determinations. But, it is rather likely that the nitrogen accounting for the putative high protein contents is due to insoluble cell wall bound hydroxyproline-rich glycoproteins. Due to their extreme insolubility, these  compounds  cannot  be  digested  easily,  and  thus,  they  do  not  contribute to the nutritiousness of M. oleifera leaves.
In contrast to classical glucosinolates, those occurring in M. oleifera are characterized by an attachment of a rhamnose to the aglycone. In consequence, the products generated during the myrosinase-cata-lysed hydrolysis correspond to non-volatile rhamnosides of isothiocyanates. Since over time, olfactorily active substances emerge, the rhamnose moiety has to be cleaved off, putatively by a corresponding rhamnosidase.