The Effect of Glycosylation on Biodistribution and Cytotoxicity of 99mTc-radiolabeled Luteolin

Purpose: Luteolin (Lu) and its glycosylated derivative, luteolin-7-O-glucoside (LuG), are the main bioactive flavonoids reported in the Scutellaria genus. Still, in vivo biodistribution and cytotoxic effects on cancer cells remain unrevealed. This study investigated the biodistribution and cytotoxic effects of Lu and LuG on cancer cell lines, particularly hepatic carcinoma (HepG2). Methods: Lu and LuG were isolated from S. pinnatifida extracts, and the structures were confirmed by ¹H-NMR spectroscopy. Radiolabeling was performed to assess their biodistribution in Wistar-Albino rats using SPECT imaging and organ radioactivity was measured. Organs were harvested and radioactivity quantified to determine tissue accumulation. Cytotoxicity was evaluated via MTT assay on normal (HUVEC) and cancer (HepG2, SW480) cell lines. Flow cytometry analyzed apoptosis/necrosis and cell cycle arrest after treatment. Results: LuG exhibited preferential accumulation in the liver (~28.7%) and significant cytotoxicity on HepG2 cells. Flow cytometry indicated non-apoptotic cell death and G1/S phase cell cycle arrest in HepG2 cells treated with LuG, whereas Lu showed less accumulation and cytotoxicity. Biodistribution data revealed lower accumulation in other organs, and LuG had negligible toxicity on non-hepatic cells (HUVEC, SW480). Overall biodistribution analysis revealed lower off-target accumulation, further supporting the hepatic selectivity of LuG. Conclusion: This study provides the first integrated evidence of the liver-targeted biodistribution and selective anticancer effects of LuG. These findings demonstrate LuG as a candidate therapeutic for hepatocellular carcinoma. These results emphasize the importance of pharmacological evaluation of flavonoid glycosides and support preclinical development of LuG as a targeted anticancer agent.