Nutrients, secondary metabolites and anti-oxidant activity of Moringa oleifera leaves and Moringa-based commercial products

Abstract Moringa oleifera is a multipurpose plant with a wide range of applications. The leaves of M. oleifera (MOLs) collected from Limpopo, Mpumalanga and Gauteng provinces, as well as commercially sold Moringa-based products (MBCPs), were investigated for nutrient content, secondary metabolites profiles and antioxidant activity. Fourier Transform infrared spectroscopy provided a rapid tool for the quality assurance and authentication of MBCPs. Marker bands representing the OH stretch, aromatic group stretch (C = C), sharp absorption band (C = O) and typical aliphatic CH stretch, were observed in the MBCPs. The profiling of the methanol extract using UPLC-Q-TOF-MS revealed 19 compounds namely; flavonoids and phenolic acid derivatives identified as, Glucomoringin (1), 3-Caffeoyl quinic acid (2), 3-p-Coumaroylquinic acid (3), 4-Caffeoyl quinic acid (4), Acetyl 4-(α- l -rhamnopyranosyloxy) benzyl glucosinolate (5), Apigenin C-diglycoside (6), 4-p-Coumaroyl quinic acid (7), 4-Feruloylquinic acid (8), Quercetin-3-O-rutinoside (9), Apigenin C-hexose (10), Quercetin-7-hexose (11), Quercetin-3-hexose (12), Quercetin-3-acetyl-hexose (13), Kaempferol-3-O-rutinoside (14), Luteolin-7-O-glucoside (15), kaempferol-3-hexose (16), Cyanidin hexose (17), Isorhamnetin-hexose (18) and Kaempferol acetyl hexose (19). A strong comparability was observed between antioxidant activity and nutrient content of the leaves. Leaves from Limpopo exhibited the highest nutrient content and lowest IC50 value (19.1 ± 0.26 µg/mL) indicating satisfactory antioxidant activity, followed by leaves harvested from Mpumalanga (22.8 ± 0.60 µg/mL) and Gauteng (24.2 ± 0.21 µg/mL). Geographical location played a limited role in the secondary metabolites profiling of M. oleifera. All the leaf specimens studied contain adequate antioxidants, nutrients and therefore useful in the manufacture of food, body products, drugs and phyto-pharmaceuticals with therapeutic value.