Phenolic Extraction of Moringa oleifera Leaves in DES: Characterization of the Extracts and Their Application in Methylcellulose Films for Food Packaging

In this work, a qualitative study of the phenolic content of Moringa oleifera leaves (MO), extracted with deep eutectic solvents (DES) based on choline chloride (ChCl) with lactic acid (LA) or glycerol (GLY), was performed by high-resolution mass spectrometry (HPLC-DAD-ESI-MSn). The two solvents (DES-LA and DES-GLY) extract similar classes of phenolics, and ten compounds were identified. The antioxidant profile was also studied (TPC, TFC, DPPH, FRAP, ORAC, and ABTS). Both solvents show an efficient extraction of phenolic compounds and high antioxidant capacity was verified for the extracts. However, the DES-Gly have a higher capacity for polyphenolic extraction (TPC led to 38.409 +/- 0.095 mg GAE.g(-1) and 2.259 +/- 0.023 mg QE.g(-1) for TFC). Films based on methylcellulose (MC) containing different amounts of DES or MO extracts, acting as plasticizers, were developed and characterized regarding their mechanical, optical, water vapor permeability, and microstructural properties. All films are uniform, clear, and transparent with smooth, homogeneous surfaces. It was found that the presence of more than 10% of MO extract and/or DES provided more flexible films (Eb for MC 2%_DES 20% achieved 4.330 +/- 0.27 %, and 8.15 +/- 0.39 % for MC 2%_MO 20%) with less mechanical and barrier resistance. The ultimate objective of this study was to provide information that could assist in the development of antimicrobial active methylcellulose films for sliced wheat bread packaging.

Automated summary

In this study, the phenolic content of Moringa oleifera leaves was qualitatively analyzed using deep eutectic solvents (DES) based on choline chloride (ChCl) with lactic acid (LA) or glycerol (GLY). High-resolution mass spectrometry was used for analysis. The study found that both DES-LA and DES-GLY were effective in extracting phenolic compounds, and ten compounds were identified. The antioxidant profile of the extracts was also studied, showing high antioxidant capacity. Films based on methylcellulose (MC) with varying amounts of DES or MO extracts were developed and characterized. The presence of MO extract and DES in the films increased flexibility but reduced mechanical and barrier resistance.