Characterization of the glucosinolates and isothiocyanates in Malunggay (Moringa oleifera L.) extracts and determination of their myrosinase activity and anticancer properties

The research investigated the properties of glucosinolates in locally grown malunggay (Moringa oleifera L.) samples including a chemical analysis of the major components in the edible parts, their hydrolytic products, the activity of the hydrolytic enzyme, and the anticancer potential of extracts derived from the plant. HPLC analysis showed higher levels of glucosinolates in seeds than in leaves of malunggay. Boiling resulted in increased total glucosinolate content in the seeds however, the opposite effect was observed in the leaves. Glucomoringin [4-(α-L-rhamnopyranosyloxy) benzyl glucosinolate] was identified by LC-MS analysis of both intact and desulfated samples as the major glucosinolate in the malunggay extract, confirming previously published work on Moringaceae. Further evidence for the identity of the major compound was seen in the hydrolysis products which were obtained from an optimized procedure. 4-(α-L-rhamnopyranosyloxy) benzyl isothiocyanate and its acetylated derivative, 4-(4’-O-acetyl-α-L-rhamnopyranosyloxy) benzyl isothiocyanate were found as the major breakdown products in the reaction catalyzed by exogenous myrosinase. The hydrolysate also yielded benzyl isocyanate. Significant amounts of isothiocyanates were detected in seeds and leaves. These may be inherent in the samples or may have been formed during a sample preparation step. The values however markedly increased when samples were made to undergo hydrolysis in the presence of added enzyme. M. oleifera contains an active De La Salle University 6 hydrolytic enzyme myrosinase, as evidenced by the ability of its extract to catalyze the hydrolysis of sinigrin. The enzyme has a KM of 0.032 mM and Vmax of 0.932 g-1 min -1 for sinigrin. The ability of malunggay extracts to scavenge free radicals was measured using the DPPH assay. In this study the scavenging potential was seen to increase with increased amounts of extract. The bioactivity of the malunggay extracts (juice and hydrolysate) was assessed by determining its