Renoprotective Potential of Beetroot Spent Extract Under Hyperglycemic Conditions

Diabetic nephropathy is a major complication of diabetes mellitus, primarily driven by hyperglycemia-induced oxidative stress and renal tubular cell injury. Beetroot (Beta vulgaris L.) is rich in antioxidant phytochemicals, and its industrial processing generates large amounts of spent material that may retain significant bioactive compounds. This study evaluated the phytochemical profile, antioxidant capacity, and renoprotective potential of beetroot spent extracts under hyperglycemic conditions. Beetroot spent material was extracted using hot water and 70% ethanol. Total phenolic, flavonoid, and betalain contents were quantified, and antioxidant activity was assessed using the 2,2'-azino-bis(3-ethylbenzothiazoline-6-sulfonic acid) (ABTS) radical scavenging assay. Phytochemical characterization was performed by ultra-high-pressure liquid chromatography-electrospray ionization-quadrupole time-of-flight mass spectrometry (UHPLC-ESI-QTOF-MS). Cytotoxicity was evaluated in peripheral blood mononuclear cells, SH-SY5Y, HEK-293, and MDA-MB-231 cells using the 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) assay. Renoprotective effects were investigated in HEK-293 renal tubular cells cultured under normal (5.5 mM) and high-glucose (200 mM) conditions. UHPLC-ESI-QTOF-MS was used to identify over 80 phenolic and flavonoid compounds including quercetin, epicatechin, and epigallocatechin gallate. The hot water extract exhibited superior antioxidant activity, achieving approximately 90% ABTS radical inhibition. Beetroot spent extract showed no cytotoxicity at concentrations below 1 mg/mL and significantly restored HEK-293 cell viability (>90%) under high-glucose conditions at concentrations ≥31.25 µg/mL. In conclusion, beetroot spent water extract possesses strong antioxidant and renoprotective activities against hyperglycemia-induced renal cell damage, supporting its valorization as a sustainable functional food ingredient for diabetes-related health applications.