Green downstream processing using supercritical carbon dioxide, CO2-expanded ethanol and pressurized hot water extractions for recovering bioactive compounds from Moringa oleifera leaves

• A green platform for downstream processing of moringa leaves was developed based on a 3-step.
• ScCO2, CXE and PHWE extractions were optimized in terms of yield.
• GC–MS and HPLC–ESI–QTOF–MS allowed the characterization of the three fractions.
• PHWE fraction presented higher antioxidant activity than CXE fraction.
• PHWE fraction was higher in total phenolics while CXE fraction had more flavonoids.

A green platform based on a three-step downstream processing including the use of supercritical carbon dioxide (ScCO2), carbon dioxide-expanded ethanol (CXE) and pressurized hot water (PHWE) extractions has been developed to obtain different fractions from Moringa oleifera leaves. Each process was optimized based on the extraction yield. Optimal extracts were functionally characterized by measuring total phenolic (TPC) and total flavonoid contents (TF). The antioxidant activity by TEAC assay was also tested. Moreover, a chemical characterization of the extracts was performed by GC–MS and HPLC–ESI–QTOF–MS. The extraction yields of the optimized process were 3.1, 29.5 and 30.2% respectively. The extraction of total phenolics was higher in PHWE than in CXE extract (62.4 vs. 20.3 mg GAE/g leaves) while TF showed the opposite (3.8 vs. 9.6 mg quercetin/g leaves respectively). ScCO2 fraction was rich in fatty acids such as α-linoleic acid and alkanes. CXE fraction was richer in glycosylated flavonoids than PHWE while the latest fraction was richer in phenolic acids, which could explain the higher antioxidant activity of this fraction (13.4 mmol Eq trolox/100 g dry leaves) compared to CXE (6 mmol Eq trolox/100 g dry leaves).

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