Two rare flavonoid glycosides from Litsea glutinosa (Lour.) C. B. Rob.: experimental and computational approaches endorse antidiabetic potentiality

**Background:** Diabetes mellitus is a global health crisis affecting 537 million adults (2021), projected to reach 783 million by 2045. Current therapies often fail to sustain glucose control or prevent complications. Litsea glutinosa (Lauraceae) is used in traditional medicine for diabetes, but antidiabetic evidence from its leaves was lacking. This study aimed to isolate phytoconstituents from L. glutinosa leaves and evaluate antidiabetic activity via in vivo and in silico methods.

**Methods:** Leaves were collected from Chittagong, Bangladesh. Methanol extract was partitioned (petroleum ether, chloroform, ethyl acetate). The chloroform fraction (320 mg) underwent gel permeation chromatography on Sephadex LH-20, followed by preparative TLC to yield compound 1 (5.0 mg) and compound 2 (3.0 mg). Structures were elucidated using 1H and 13C NMR, COSY, HSQC, HMBC, and ESI-MS. For in vivo study, 25 male Swiss albino mice (30-35 g) were divided into 5 groups (n=5): normal control, diabetic control (STZ 40 mg/kg i.p. for 5 days), metformin 50 mg/kg, MELG 300 mg/kg, and MELG 500 mg/kg. Fasting blood glucose was measured on days 3, 5, and 7. Molecular docking used AutoDock Vina against human aldose reductase (PDB: 1EL3) and α-amylase (PDB: 3BAJ). ADMET and toxicity were predicted using admetSAR and ProTox II.

**Key Results:** Compound 1 (4′-O-methyl (2″,4″-di-E-p-coumaroyl) afzelin, C40H34O14) and compound 2 (quercetin 3-O-(2″,4″-di-E-p-coumaroyl)-α-L-rhamnopyranoside, C39H32O15) were isolated. This is the first report of both from a Litsea species. In vivo, untreated diabetic control blood glucose rose to 16.3±3.15 mmol/L by day 7. MELG 300 mg/kg significantly reduced glucose to 6.0±0.12 mmol/L (p<0.05, 63.19% inhibition). MELG 500 mg/kg reduced glucose to 5.43±0.12 mmol/L (p<0.01, 66.69% inhibition), comparable to metformin (4.26±0.32 mmol/L, 73.87% inhibition). Docking showed compound 1 and 2 had binding affinities of -10.3 and -11.0 kcal/mol against aldose reductase (vs. IDD384: -9.5 kcal/mol), and -9.4 and -8.9 kcal/mol against α-amylase (vs. acarbose: -7.6 kcal/mol). PASS analysis predicted antidiabetic activity (Pa>0.33). ADMET predicted excellent human intestinal absorption, no CYP inhibition, and LD50 of 5000 mg/kg (class V).

**Clinical Implications:** The methanol extract of L. glutinosa leaves demonstrates significant glucose-lowering effects in a diabetic mouse model, with the 500 mg/kg dose approaching metformin efficacy. The isolated flavonoid glycosides show strong in silico inhibition of α-amylase and aldose reductase, key targets for glycemic control and prevention of diabetic complications. The favorable ADMET and safety profile (LD50 5000 mg/kg) supports potential for human use. However, these findings are preliminary; further studies are needed to validate mechanisms, conduct chronic toxicity, and explore clinical applications. The plant could serve as a natural source for developing antidiabetic therapies.