Valorization of various nut residues grown in Turkiye: Antioxidant, anticholinesterase, antidiabetic, and cytotoxic activities

The utilization of plant-based residues has been extensively employed for the control of diverse illnesses, owing to their safety and minimal adverse effects. In the current study, it was aimed for the characterization of the bioactive, enzyme inhibitory, and cytotoxic activities of fresh pistachio shell skin (FPSS), green walnut husk and walnut membrane (GWH), almond outer shell and inner brown skin (ASIS), as well as peanut husk and inner skin (PHIS) to be used as industrial food processing by-products. The results showed that the samples exhibited different extraction yields, with GWH having the highest percentage at 15.18%, followed by FPSS at 12.81%, ASIS at 10.29%, and PHIS at 7.80%. FPSS had the highest total phenolic content (16.28 mg gallic acid equivalents (GAE)/g) as well as the best antioxidant capabilities for DPPH (8.96 mg Trolox equivalent (TE)/g), FRAP (11.46 mg TE/g), and ABTS (22.38 mg TE/g) assays. FPSS was followed by PHIS, ASIS, and GWH, respectively. Moreover, the extracts exhibited relatively low activity against acetylcholinesterase, α-glucosidase, and α-amylase compared to standard acarbose or galantamine. Furthermore, the extracts may have the potential to induce cytotoxic effects, varying from moderate to mild, on both cancerous (IC = 454.55-617.28 μg/mL) and healthy cells (IC = 438.60-490.20 μg/mL). The results of this research showed that shell residues of nut hold promise for a variety of industrial applications spanning the food, pharmaceutical, and cosmetic sectors.