Research background. Sorghum bran, although considered as an agricultural waste, is an abundant source of various bioactive compounds. These bioactive compounds are specific to extraction with particular solvents and therefore ionic liquid and three different conventional solvents, viz., anhydrous methanol, acidified methanol and water were employed in this work. Experimental approach. To evaluate the phytochemicals in the different sorghum bran extracts, total phenol content, flavonoids, condensed tannins and anthocyanins were determined as per standard protocols. LC/MS/MS analysis of extracts was also performed for their phenolic profiling. The antioxidant activity of the extracts was estimated via three assays: DPPH, ABTS and CUPRAC. The antibacterial activity against two most opportunistic food borne pathogens: Escherichia coli and Staphylococcus aureus were measured by agar well diffusion assay and minimum inhibitory concentration (MIC) was determined by serial dilution method. Results and conclusions. Following similar process of extraction, ionic liquid extract of sorghum bran exhibited highest yield (14.9±0.7 %) which indicated to the various possible interactions like Van der Waals forces, H-bonding, hydrophobic and cation-π which ionic liquid can offer in contrast to other conventional solvents, though total phenol content was observed to be only (7.41±0.73 mg GAE/g sample dry weight (DW)). The hydrophobicity of the ionic liquid also helped in efficient extraction of condensed tannins (63.15±2.13 mg CE /g sample DW) which resulted in significant antioxidant activity of the ionic liquid extract (DPPH: 85.22±1.21 µmol/g sample DW; ABTS: 100.75±0.93 µmol/g sample DW; CUPRAC: 63.24±1.86 µmol/g sample DW). An interesting revelation reported in this work is the inability of DPPH assay to evaluate antioxidant activity in acidic environment. The anhydrous methanolic extract of sorghum bran displayed pH sensitivity making the extract beneficial for certain applications. Qualitative analysis of extracts revealed greater number of phenolic compounds to be present in methanol and distilled water extracts. Moreover, various derivatives of apigenin and luteolin were also observed in all the four extracts. In addition, the acidified methanol extract of the sorghum bran exhibited antimicrobial property at a concentration of 12 mg/mL. A larger inhibition zone was observed against Escherichia coli in comparison to Staphylococcus aureus while the MIC against these two bacteria was found to be 2.2 and 1.1 mg/mL, respectively. Novelty and scientific contribution. This paper presents the first information on the application of ionic liquids as extracting phase for sorghum bran polyphenols and the quantification of such extracts. As evident from the study, each solvent has its own role in extraction of bioactive compounds. This work also proves that sorghum bran imparts antibacterial activity against foodborne pathogens.
Currently, a variety of petroleum based plastic materials are dominating the packaging industries owing to their durability, versatility, light-weight and most importantly their cost-effectiveness. This trend is being overcome by the growing concern towards environmental pollution caused by the production as well as the disposal of these materials and the presence of toxic substances that could migrate from the packaging material to the product causing potential risk to human health while using the product. Biopolymers, is a promising green alternative to synthetic, non-degradable polymers. These natural polymers (polysaccharides, proteins and lipids) are much more suitable components for food as well as non-food packaging applications due to their qualities of renew-ability, degradability and edibility. However, poor water vapour barrier properties of carbohydrates (polysaccharides) and proteins, and low elasticity of lipids are the main limitations for their use as commercial packaging materials. In this regard plasticizers provide the necessary workability to biopolymers. This review gives a brief insight into their plasticization effects, types, properties along with their effect and recent applications on bio-based materials, with special reference to a new class of plasticizers, Ionic liquids.
Ionic liquid (1‐butyl‐3‐methyl imidazolium chloride—[bmim]Cl) was used as a plasticizer alternative to enhance the mechanical strength of the starch‐zein composite films. Additionally, sorghum bran extract (SBE) was utilized as a sustainable source of bioactive compounds to introduce the antimicrobial activity to the composite films. [Bmim]Cl provided better solubilization capacity thereby enhancing the compatibility of film components. Thus, [bmim]Cl substantially improved the tensile strength and elongation at break of the ionic liquid plasticized (8.93 ± 1.59 MPa and 29.53 ± 0.86%) as well as sorghum bran functionalized films (8.99 ± 0.42 MPa and 21.91 ± 0.76%). Incorporation of SBE to the potato starch‐zein film solution enhanced opacity and attributed antioxidant properties to the composite film and that endorsed the possibility of inhibiting lipid peroxidation. Furthermore, the sorghum bran functionalized films possessed antimicrobial activity against Escherichia coli, making them appropriate for active packaging applications.
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