Phytochemical Properties and Inhibitory and Antioxidant Effects of the Decoction, Infusion and Hydro-Alcoholic Extract of Nepeta Race-mosa on α-Amylase and α-Glucosidase

As an important plant belonging to the Nepeta genus, Nepeta racemosa has been reported to be widely used in traditional medicine. The present study was conducted to investigate the phytochemical content and antioxidant and antidiabetic potential of the decoction, infusion and hydro-alcoholic extract of this plant. The total phenolic content of the samples was determined using a slightly- modified Folin–Ciocalteu method. The DPPH free radical scavenging method was used to evaluate the antioxidant activities, and the Vanillin-Sulphuric Acid Method for the saponin content of the extract. Moreover, their inhibitory effects on α-amylase and α-glucosidase were investigated based on standard methods. The phenolic content of the plant decoction was found to be 222.8 mg of gallic acid equivalent per gram of dried extract and its flavonoid content 87.8 mg of quercetin equivalent per gram of dried extract. The highest saponin content obtained was associated with the hydro-alcoholic extract of the plant with 41.9 mg of quillaja equivalent per gram of dried extract. The plant decoction also showed the highest potential compared to the other samples in terms of antioxidant properties investigated using the DPPH and FRAP methods. Furthermore, the plant decoction showed great potential in terms of its inhibitory effects on α-amylase with 9.45 µmol of acarbose equivalent per gram of dried extract, and α-glucosidase with 33.57 µmol of acarbose equivalent per gram of dried extract. According to the results, Nepeta racemosa was found to exhibit high levels of antioxidant and antidiabetic abilities, which are directly proportional to its phenolic and flavonoid contents.