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.