Volatile profiling of Cinnamomum heyneanum and Cinnamomum Palghatensis and in vitro and in silico antidiabetic activity of essential oil nanoemulsions

Essential oil nanoemulsions (EONs) of two wild cinnamons, Cinnamomum heyneanum (CH) and Cinnamomum Palghatensis (CP), were formulated, characterized and investigated for their antidiabetic activity. Leaf essential oils (EOs) were extracted and characterized by GC-MS and GC-FID. Two sets of EONs were formulated and characterized by zeta analyzer, viscometer and TEM. Antioxidant activity was studied using DPPH, ABTS, superoxide, hydroxyl and hydrogen peroxide assays. Antidiabetic activity was evaluated by α-amylase inhibition, α-glucosidase inhibition, glucose uptake and glucose-stimulated insulin secretion assays. In silico studies were performed to support the efficacy. Methyl eugenol (60.3 %), safrole (27.8 %) in CH EO and bicyclogermacrene (19.5 %), (E)-caryophyllene (14 %) in CP EO were major components. Of two sets of EONs, 1:2 ratio showed better hydrodynamic average diameter [CH 42.9±0.78 nm & CP 27.9±1.70 nm] and better zeta potential [CH −38.4±0.85 mV & CP −38.4±0.45 mV (1st day)]. TEM observation showed that 1:2 ratio EONs were spherical with an average diameter of 85 nm (CH) and 8.98 nm (CP). Both CH and CP showed remarkable antioxidant activity. CP showed better α-glucosidase inhibition (IC50 0.599±0.008 mg/mL), enhanced glucose uptake (0.53±0.08 fold vs. control) and insulin secretion (1.40±0.06 fold vs. control). In silico analysis reveals that all major components of CH and CP interact with key residues of the protein targets associated with diabetes, α-amylase, α-glucosidase, insulin receptor, Glugagon like peptide1 Receptor and Glut 4. In vitro and in silico studies revealed that EON of CH and CP have pharmacological properties due to the presence of various compounds against diabetes mellitus.