Phenolic metabolite profiling of Moringa oleifera Lam waste under different drying methods and extraction solvents

The processing of Moringa (Moringa oleifera) generates a substantial amount of waste, rich in bioactive compounds, which is often discarded. The objective of this study is to investigate the effects of different drying techniques and solvent extraction methods on the bioactive composition, antioxidant, and antifungal activities of M. oleifera waste (twigs). M. oleifera twigs were collected from an orchard at the University of Limpopo and exposed to three drying techniques: freeze drying (FD), sun drying (SD), and oven drying (OD). The dried materials were then ground into powder and extracted with varying solvents: distilled water (H₂O), 50 % ethanol (EtOH50 %), and 100 % ethanol (EtOH100 %). Total phenolic content (TPC), extract yield, antifungal activity against Botrytis spp., 2,2-diphenyl-1-picryl hydrazyl (DPPH), and 2,2-azino-bis (3-ethylbenzothiazoline-6-sulphonic Acid) (ABTS) antioxidant activities were measured, whilst ultra-performance liquid chromatography-mass spectrometry (UPLC-MS/MS) was used for phenolic compounds profiling. The results showed that OD-EtOH50 % extract had the highest extract yield (13.0 %), TPC (0.52 mg GAE/g DW), DPPH (1.69 IC₅₀, mg/mL), and ABTS (1.05 IC₅₀, mg/mL), and antifungal activity against Botrytis spp. (0.06 MIC, mg/mL). Furthermore, SD-EtOH50 % extracts tentatively identified approximately 24 phenolic metabolites. This study showed that Moringa waste, particularly OD-EtOH50 % extracts, presents a potential source of bioactive compounds for postharvest preservation, contributing to sustainable food systems and promoting a circular bioeconomy. Further research could optimize drying methods and extraction solvent concentration for obtaining high bioactive extract from Moringa waste through a cost- and energy-effective method.