Inhibition of Carbohydrate Digestive Enzymes by a Complementary Essential Oil Blend: In Silico and Mixture Design Approaches

El Hassania Loukili ^1* Mouhcine Fadil ² Amal Elrherabi ³ Mohammed Er-Rajy ² Mohamed Taibi ³ Khalil Azzaoui ² Rachid Salghi ⁴ Rachid Sabbahi ^4* Mohammed M Alanazi ⁵ Larbi Rhazi ⁶ Aleksandar Széchenyi ⁷ Mohamed Siaj ⁸ Belkheir Hammouti ¹

• ¹ Euromed University, Fez, Fes-Meknes, Morocco
• ² Sidi Mohamed Ben Abdellah University, Fes, Morocco
• ³ Mohamed Premier University, Oujda, Morocco
• ⁴ Université Ibn Zohr, Agadir, Souss-Massa, Morocco
• ⁵ King Saud University, Riyadh, Riyadh, Saudi Arabia
• ⁶ UniLaSalle, Beauvais, Hauts-de-France, France
• ⁷ University of Pécs, Pécs, Baranya, Hungary
• ⁸ Université du Québec à Montréal, Montreal, Quebec, Canada

The increasing demand for natural alternatives in diabetes treatment has focused attention on plant-derived metabolites, particularly essential oils (EOs) with bioactive properties. This study aims to optimize an EO mixture to inhibit two key enzymes involved in glucose digestion: pancreatic α-amylase and intestinal α-glucosidase. The EOs tested were extracted from three Moroccan medicinal plants: false yellowhead (Inula viscosa L.), rose geranium (Pelargonium graveolens L'Hér.), and lemongrass (Cymbopogon citratus (DC.) Stapf.). The Gas chromatography coupled with mass spectrometry (GC-MS) analysis identified 32 metabolites in P. graveolens, with citronellol (18.67 %), eucalyptol (13.30 %), and 2-octen-1-ol (8.12 %) as the major metabolites . In I. viscosa, 18 metabolites were found, dominated by 2-camphanol acetate (51.12 %) and camphol (19.32 %). C. citratus, contained 23 metabolites, with α-citral (24.70 %) and 2-isopropenyl-5-methylhex-4-enal (29.25 %) being the key metabolites. Using a statistical mixture design, different EO ratios were evaluated for their inhibitory effects on these enzymes, which play crucial roles in glucose absorption and postprandial glucose regulation. A complementary action was observed in specific EO combinations, significantly enhancing enzyme inhibition compared to individual oils. The optimal formulation for α-glucosidase inhibition was a binary mixture of 73 % C. citratus and 27 % P. graveolens. In comparison, the best blend for α-amylase inhibition consisted of 56 % P. graveolens and 44 % I. viscosa. Density functional theory (DFT) calculations supported these findings by elucidating the electronic properties of the key volatile metabolites and confirming their electrophilic nature and interaction potential with the enzymes. Molecular docking simulations further provided preliminary theoretical insights, suggesting that these phytochemicals may exhibit more substantial inhibitory effects than acarbose, a widely used antidiabetic drug. These findings suggest that optimized EO formulations hold significant potential as natural alternatives for managing hyperglycemia and developing novel therapies for diabetes.