Biological properties and HPLC analyses of four medicinal plants extracts obtained at different extraction temperatures

In the present study, extracts of four medicinal plants (Cajanus cajan, Carica papaya, Morinda morindoides, and Senna alexandrina) obtained at two different extraction temperatures (24 and 45°C) were investigated for their polyphenolic contents, antioxidant, and enzyme inhibitory properties. For instance, extracts of the studied species yielded total phenolic and flavonoid contents in the range of 17.8–66.3 mg GAE/g and 4.18–26.8 mg RE/g, respectively. High performance liquid chromatography (HPLC) coupled with antioxidant assays (HPLC-FRAP and HPLC-DPPH) was employed for direct identification of antioxidant compounds. The extracts showed moderate to high antioxidant potentials in various assays performed (radical scavenging activity: 10.15–240.08 mg TE/g; reducing activity: 24.88–229.59 mg TE/g; metal chelating activity: 5.56–18.32 mg EDTAE/g and total antioxidant capacity: 1.40–2.18 mM TE/g). Additionally, the extracts were found to exert inhibitory properties against all the studied enzymes (anti-acetylcholinesterase: 1.80–2.29 mg GALAE/g; anti-butyrylcholinesterase: 0.19–3.13 mg GALAE/g; anti-amylase: 0.39–0.58 mmol ACAE/g; anti-glucosidase: 0.17–1.36 mmol ACAE/g and anti-tyrosinase: 60.97–73.71 mg KAE/g). Of all, C. cajan extracts were revealed to be the best antioxidants and inhibitors of most enzymes. Therefore, this study demonstrated the pharmacological potentials of the four medicinal plants, especially C. cajan as viable sources of phyto-ingredients that could be of interest in nutraceutical development. Novelty impact statement: The methanol extracts from four medicinal plant with different extraction temperatures (24 and 45°C) were investigated. HPLC-DPPH and HPLC-FRAP methodologies were used. Different levels of phenolics in the tested extracts were determined. Cajamus cajan extracts were found to be the best one in the antioxidant assays. Our findings could be opened valuable windows in the further pharmaceutical studies and applications.