Justicia gendarussa Burm. f. leaf extract protects against glucotoxicity-induced pancreatic β-cell dysfunction and...

The present study aimed to develop a Justicia gendarussa Burm.f. leaf extract enriched with flavonoids and to investigate its antidiabetic mechanisms, particularly its ability to enhance pancreatic β-cell function and prevent β-cell death under hyperglycemic conditions. The extract, prepared using ethanol via the Soxhlet extraction method, yielded 15.06% dry extract by weight and exhibited a dark green, viscous appearance. Phytochemical analysis revealed a high flavonoid content (172.10 mg quercetin equivalents/g extract) and a moderate phenolic content (23.47 mg gallic acid equivalents/g extract). Antioxidant activity, evaluated using 2,2-diphenyl-1-picrylhydrazyl and 2,2'-azino-bis(3-ethylbenzothiazoline-6-sulfonic acid assays, demonstrated potent radical scavenging capacity, with IC₅₀ values of 1.15±0.14 and 0.42±0.07 mg/ml, respectively. High-performance liquid chromatography analysis identified vitexin as the one bioactive flavonoid in the extract with amount of 0.19±0.02 mg/g extract. In vitro studies using INS-1 pancreatic β-cells exposed to high glucose concentrations showed that the extract at concentrations of 50 and 100 µg/ml markedly increased cell viability and reduced intracellular reactive oxygen species levels comparable with those of normal-glucose controls. The antioxidant effect of the JG extract was mediated through the upregulation of key antioxidant genes, Nrf2 and Trx. Furthermore, the extract reduced apoptosis by 25.59%, an effect comparable with that of 10 µM vitexin. Gene expression analysis revealed that the extract markedly upregulated pancreatic and duodenal homeobox 1 mRNA levels compared with the high-glucose group, suggesting enhanced insulin synthesis via activation of key transcriptional regulators. In conclusion, the cytoprotective effects of JG extract are mediated through antioxidant activity, inhibition of apoptosis and stimulation of insulin gene expression. Further molecular and in vivo studies, along with clinical validation, are warranted to support the development of this herbal extract as a complementary therapeutic strategy for managing type 2 diabetes.