PTP1B is a deceptively simple target with an outsized influence on human metabolism. The enzyme works by removing phosphate groups from tyrosine residues on signaling proteins, and among its substrates are the insulin receptor and downstream mediators of the insulin signaling cascade. When PTP1B runs unchecked, it effectively short-circuits insulin signaling, forcing cells to become less responsive to the hormone, a hallmark of type 2 diabetes. Genetic studies in mice made the case decades ago: animals lacking functional PTP1B show enhanced insulin sensitivity and resistance to diet-induced obesity without obvious developmental defects. That biological profile has made the enzyme a magnet for pharmaceutical chemists, but developing selective inhibitors has proved difficult because PTP1B shares a highly conserved catalytic pocket with closely related phosphatases, and the charged active site makes it hard to design drug-like molecules that bind tightly and get into cells. Natural products, with their structural diversity and often favorable safety profiles, remain an important hunting ground for new chemotypes against this target.

The Korean and Vietnamese team turned their attention to hemp seed cake, the protein- and polyphenol-rich solid residue left after oil is pressed from seeds of Cannabis sativa. Hemp cultivation for food and feed is expanding worldwide, and the cake is already valued as a source of protein, minerals, and phenolic compounds for applications such as fortified bread. Previous studies had identified phenylpropionamides in hemp seed husks and shown that hemp hull fiber and its constituent compounds can shape the human gut microbiome, but the cake itself had not been systematically explored for enzyme inhibitors relevant to metabolic disease. Using chromatographic separation guided by spectroscopic analysis and comparison with published data, the researchers identified two compounds: N-trans-caffeoyltyramine and N-trans-feruloyltyramine. Both belong to a family of cinnamoyl phenethyl amides, molecules in which a hydroxycinnamic acid moiety, the same aromatic framework found in coffee’s chlorogenic acid chemistry, is joined by an amide bond to tyramine, a phenolic amine.

The enzyme assays delivered the headline result. N-trans-caffeoyltyramine inhibited PTP1B with a half-maximal inhibitory concentration, or IC50, of 62.0 micromolar, while its feruloyl cousin proved considerably more potent, achieving an IC50 of 14.0 micromolar. For a pair of small phenolic amides isolated from a food-industry residue, those numbers are respectable, particularly because the compounds were tested as purified molecules rather than as a crude extract whose activity might be inflated by synergistic effects. The difference in potency between the two is chemically informative: the feruloyl compound carries a methoxy group in place of one of the caffeoyl compound’s hydroxyl groups, and the extra methyl ether appears to help the molecule engage the enzyme, a structure-activity clue that could guide the design of more potent analogs.

To understand how the more potent compound suppresses the enzyme, the team performed kinetic analysis, the classical enzymology method that reveals where and how an inhibitor binds. The results showed that N-trans-feruloyltyramine acts as a mixed inhibitor with an inhibition constant, Ki, of 30.9 micromolar. Mixed inhibition means the compound can bind both the free enzyme and the enzyme-substrate complex, indicating that it does not sit exclusively in the catalytic pocket but also makes contact with adjacent or allosteric regions of the protein. From a drug-discovery standpoint, that behavior is potentially advantageous. Inhibitors that engage sites outside the highly conserved catalytic cleft are more likely to discriminate between PTP1B and its close relatives such as T-cell protein tyrosine phosphatase, which has long frustrated efforts to develop selective compounds. The mixed-mode profile also suggests the feruloyl amide exploits binding determinants beyond the phosphate-binding loop that all members of the phosphatase family share.

Molecular docking simulations provided a structural picture consistent with the kinetics. Docking places a small molecule into a three-dimensional model of the target protein and scores the predicted binding pose and interaction energy. The simulations showed that N-trans-feruloyltyramine can occupy the PTP1B active-site region and form specific interactions with residues lining the pocket, including the hydrogen-bonding contacts expected between its phenolic hydroxyls and the polar residues that normally recognize phosphorylated tyrosine substrates. The aromatic rings and amide linkage of the compound allow it to span a meaningful stretch of the binding site, anchoring itself through multiple simultaneous contacts. While docking is a computational hypothesis rather than proof, the agreement between the predicted binding mode, the measured IC50, and the kinetic signature of mixed inhibition gives the pharmacological case for the compound internal coherence that many natural-product screening hits lack.

The researchers then widened the lens with a network pharmacology analysis, a systems-level approach that has become a staple of natural-product research. The method begins by identifying putative protein targets of a compound, often through databases that link chemical structures to known or predicted targets, and then maps those targets onto disease-associated genes and signaling networks. For N-trans-feruloyltyramine, the analysis pointed toward molecular mechanisms relevant to the treatment of type 2 diabetes mellitus, connecting the compound’s PTP1B inhibition to broader insulin-signaling and metabolic pathways. Network pharmacology cannot confirm efficacy, but it generates testable hypotheses about how a food-derived molecule might exert pleiotropic effects, and it helps prioritize which cellular assays and animal models should come next. In this case, the network view supports the idea that a PTP1B inhibitor from hemp could influence glucose homeostasis through the same axis that pharmaceutical PTP1B inhibitors are designed to modulate.

Context matters for any compound isolated from a food matrix, and here the feruloyl amide has a head start. A 2025 safety assessment published in Human and Experimental Toxicology evaluated N-trans-feruloyltyramine using in vitro genotoxicity studies and a 90-day toxicity study in rats, work that provides a preliminary toxicological foundation for a molecule now being flagged as an enzyme inhibitor. The compound also occurs naturally in hemp hull fiber, where it has been shown to influence the composition of the human gut microbiome in vitro, raising the possibility that it reaches the intestinal environment in a bioactive form when hemp-derived foods are consumed. Whether oral consumption of hemp seed cake delivers blood concentrations sufficient to inhibit PTP1B in human tissues is a question the current study cannot answer, and the authors are careful to frame their findings as a basis for further investigation rather than a dietary recommendation.

The broader significance of the study lies in what it says about agricultural side streams. Hemp seed cake is produced in quantity wherever hemp oil is pressed, and much of it is undervalued relative to its chemical content. Earlier work has catalogued its proteins, minerals, polyphenols, and glycoproteins, and extrusion processing has been shown to modify its polyphenol profile and biological activities. The new results add a specific, mechanistically characterized bioactivity to that inventory: PTP1B inhibition by phenylpropionamides, with potency data, kinetic mode, docking evidence, and a disease-relevant network context. That combination is exactly the kind of package that turns a phytochemistry observation into a credible lead for functional-food or nutraceutical development.

Considerable work remains before any of this reaches a clinic or a supermarket shelf. The IC50 values, while promising, are in the low-to-mid micromolar range, well above the nanomolar potencies typical of clinical drugs, so potency optimization through structural modification or synergistic formulations would be needed. Selectivity against related phosphatases must be demonstrated experimentally, bioavailability and metabolism in vivo remain uncharacterized, and the network pharmacology predictions require validation in cellular and animal models of insulin resistance. Still, the study delivers what early-stage natural-product science is supposed to deliver: a verified chemical lead from an unexpected source, a mechanistic hypothesis grounded in kinetics and structure, and a clear map of what to test next. In the effort to find new tools against type 2 diabetes, the humble residue of hemp oil pressing has just earned a place on the list of materials worth watching.

Subject of Research: PTP1B inhibitory activity of phenylpropionamides isolated from hemp seed cake as potential antidiabetic compounds

Article Title: Inhibitory effects of phenylpropionamides from the hemp seed cake on protein tyrosine phosphatase 1B: in vitro, molecular docking, and network pharmacology approach

Article References: Cao, T. Q., Yeo, C. E., Yu, S., Chi, H. N., Tran, T. Y. N., Tuong, L.-T., Kim, J.-S., & Hahn, D. (2026). Inhibitory effects of phenylpropionamides from the hemp seed cake on protein tyrosine phosphatase 1B: in vitro, molecular docking, and network pharmacology approach. Food Science and Biotechnology. https://doi.org/10.1007/s10068-026-02293-8

Image Credits: AI Generated

DOI: 10.1007/s10068-026-02293-8

Keywords: hemp seed cake, PTP1B, phenylpropionamides, N-trans-feruloyltyramine, N-trans-caffeoyltyramine, type 2 diabetes, molecular docking, network pharmacology, enzyme inhibition, natural products, Cannabis sativa, insulin signaling