Unlocking Paeonia emodi’s Phytochemical Potential: Extraction, Quantification, and Bioassay Studies

Background: Type 2 diabetes features postprandial hyperglycaemia, impaired insulin signalling, and glyco-oxidative stress. Approaches that simultaneously attenuate intestinal carbohydrate digestion, enhance insulin receptor signalling, and limit advanced glycation end-products (AGEs) may offer superior benefit. Objective: To quantify phytochemical constituents of Paeonia emodi roots and assess multitarget antidiabetic activities—antiglycation, α-amylase and α-glucosidase inhibition, and PTP1B inhibition—across phytochemical classes and solvent fractions. Methods: Roots were ethanolic-extracted and successively fractionated with n-hexane, chloroform, ethyl acetate, and methanol. Total flavonoids, phenolics, and tannins were measured by AlCl₃ and Folin methods; alkaloids were determined gravimetrically. Bioactivities were evaluated in microplates: BSA–glucose antiglycation (Ex/Em 370/440 nm), α-amylase (DNS endpoint, A540), α-glucosidase with pNPG (A405), and PTP1B with pNPP (A405). IC₅₀ values were obtained by nonlinear regression with appropriate controls and replication. Results: P. emodi contained high flavonoids (852.67 ± 64.97 µg/mL) and tannins (394.00 ± 13.02 µg/mL), with lower phenolics (98.59 ± 29.71 µg/mL). Flavonoids displayed the strongest antiglycation effect (IC₅₀ 14.61 ± 0.93 µg/mL), while the n-hexane fraction was the most potent antiglycation extract (9.52 ± 0.34 µg/mL). For α-amylase, phenolics were most active (8.28 ± 1.07 µg/mL) and n-hexane and ethyl acetate fractions were superior (5.99 ± 0.20 and 6.09 ± 1.16 µg/mL), exceeding acarbose (20.54 ± 1.07 µg/mL). Tannins most strongly inhibited PTP1B (4.27 ± 0.20 µg/mL), and the methanol fraction was the most active extract (4.29 ± 0.26 µg/mL), followed by n-hexane (6.73 ± 0.05 µg/mL). For α-glucosidase, phenolics led among classes (5.50 ± 0.56 µg/mL), while n-hexane and methanol fractions were most potent (4.85 ± 0.06 and 5.85 ± 0.69 µg/mL). Conclusion: Paeonia emodi demonstrates a coherent multitarget antidiabetic profile. Non-polar fractions concentrate inhibitors of postprandial pathways (α-amylase/α-glucosidase and antiglycation), whereas polar fractions are enriched for PTP1B inhibition. These complementary mechanisms justify bioassay-guided isolation and standardization efforts toward phytopharmaceutical development for diabetes management.