Ultrasound-Assisted Extraction of Verbascoside from Clerodendrum glandulosum Leaves for Analysis of Antioxidant and Antidiabetic Activities

Abstract

Verbascoside (VER) is a phenylethanoid glycoside compound found in Clerodendrum species and is an important part of traditional medicine. It is found in the leaves of Clerodendrum glandulosum, which is taken as a soup or vegetable and also utilized in traditional medicine by the people of Northeast India, especially against hypertension and diabetes. In the present study, VER was extracted from C. glandulosum leaves using ultrasound-assisted extraction through the solvent extraction method (ethanol−water, ethanol, and water). The ethanol extract had the highest phenolic and flavonoid contents, viz., 110.55 mg GAE/g and 87.60 mg QE/g, respectively. HPLC and LC−MS were used to identify the active phenolic compound, and VER was found to be the main component present in the extraction with a molecular weight of 624.59 g/mol. NMR ( 1 H, 2D-COSY) analysis showed the presence of hydroxytyrosol, caffeic acid, glucose, and rhamnose in the VER backbone. Further, different antioxidant activities and antidiabetic and antihyperlipidemia enzyme markers' inhibition against VER-enriched ethanol extract were evaluated. The results showed that ultrasound extraction of polyphenols using ethanol from C. glandulosum could be a promising technique for the extraction of bioactive compounds. ■ HIGHLIGHTS1. Verbascoside was extracted by ultrasound from Clerodendrum glandulosum leaves. 2. HPLC revealed that verbascoside content was the highest (20.14%) for ethanol extracts. 3. NMR analysis revealed the presence of hydroxytyrosol, caffeic acid, glucose, and rhamnose in verbascoside. 4. Verbascoside exhibited antioxidant activities and different enzyme inhibitions.