UPLC-DAD-QTOF-MS/MS analysis of targeted poly-phenolic compounds from Moringa oleifera leaves as function of seasonal responses
F.M. Ralepele, Luke Chimuka, Yannick Nuapia, Ida Risenga
Abstract
Moringa Oleifera commonly known as miracle tree, is widely distributed in tropical and subtropical regions. It is used in traditional medicine to treat several diseases such as diabetes, hypertension, cancer, and other infections. In order to optimize the time of harvesting Moringa plant leaves, it is important to understand how various environmental factors like season affects its chemical composition especially secondary metabolites. Ultra-high-performance liquid chromatography with diode array coupled to electrospray ionization mass spectrometry (UPLC-ESI-QTOFMS) was used for the comprehensive characterization of methanol extract from Moringa Oleifera leaves from different South Africa calendar-based seasons. Some compounds such as Gallic acid, Catechin, Chlorogenic acid, Quercetin, Kaempferol, Quercetin 3,4-diglycoside, Quercetin 3-O-glucoside were quantified. Total phenolic content (TPC), total flavonoid content (TFC) and DPPH scavenging assay were measured as response to the seasonal variations. A total number of 29 Polyphenolic compounds were identified. In overall, trend of Polyphenolic content as a function of the season was as: autumn > winter > summer> spring. The highest level of Gallic acid, Catechin, chlorogenic acid, quercetin, kaempferol, quercetin 3,4-diglycoside, quercetin, TPC and TFC were found in autumn. The lowest EC50 were found in the leaves collected in autumn and winter as an indication of high antioxidant activity as compared to spring and summer. The results from the current study showed a strong evidence that seasonal variation have an impact on the secondary metabolites production. Thus, the best recommended harvesting season is autumn and summer because in winter though gave also high secondary metabolites, there is less biomass during this period.