GC–MS Based Metabolomics Strategy for Cost-Effective Valorization of Agricultural Waste: Groundnut Shell Extracts and Their Biological Inhibitory Potential

Groundnut shells (GNS) make up about 20% of the weight of a dried peanut pod, indicating a substantial amount of shell residue after groundnut processing. In primary screening, bioactive metabolites present in the various GNS extract solvents like methanol, ethanol, acetone, ethyl acetate, hexane and petroleum ether were analyzed. Further, in the quantitative analysis, total phenol and tannin content have been analyzed. Major metabolites present in the GNS extracts are Octadecane (65%), Palmitic acid (23.53%), Oleic acid (10.41%), and Lupeol (21.44%). Methanol exhibits stronger antioxidant property than other extracts due to polarity and the phenols abundance. It was reflected in IC₅₀ results of DPPH (789.36 µg/mL) and ABTS (480.11 µg/mL) radical scavenging assays. Identical results were found in antimicrobial potential against Aeromonas hydrophila, Pseudomonas aeruginosa, Klebsiella pneumoniae, and Staphylococcus aureus. Higher antibacterial activity was obtained in methanolic extracts compared to other exrtacts. Minimum inhibitory concentration (MIC) was determined against the organisms tested, in which methanol exhibited lower MIC value at 250 µg/mL, whereas other solvent extracts showed at 500 µg/mL of GNS extracts. Further, the antimicrobial ability was confirmed by analyzing growth of microorganisms with the obtained MIC and Sub-MIC range of the extracts. At MIC range, bacterial growth was completely inhibited. This research is being implemented in order to develop a zero-waste production system by converting waste into valuable bio-products, including the use of GNS as a potential antioxidant and antibacterial agent, which is cost effective when compared to other pharmaceutical agents. Graphical Abstract: [Figure not available: see fulltext.]