Phenolic Extracts from Clerodendrum volubile Leaves Inhibit Cholinergic and Monoaminergic Enzymes Relevant to the Management of Some Neurodegenerative Diseases

ABSTRACT

This study investigated the inhibitory effects of phenolic-rich extracts from Clerodendrum volubile leaves on cholinergic [acetylcholinesterase (AChE) and butyrylcholinesterase (BChE)] and monoaminergic [monoamine oxidase (MAO)] enzymes' activities and pro-oxidants [Fe²⁺ and quinolinic acid-(QA)] induced lipid peroxidation in rats brain homogenates in vitro. Free phenolic extracts (FPE) and bound phenolic extracts (BPE) were obtained via solvent extraction, and the total phenol and flavonoid contents were evaluated. The phenolic constituents of the extracts were also determined using high performance liquid chromatography coupled with diode array detector (HPLC-DAD). Our findings revealed that FPE had higher AChE (2.06 μg/mL), BChE (2.79 μg/mL), and MAO (2.81 μg/mL) inhibitory effects than BPE [AChE, 2.80 μg/mL; BChE, 3.40 μg/mL; MAO, 3.39 μg/mL]. Furthermore, FPE also had significantly (P < 0.05) higher inhibitory effects on Fe²⁺ and QA-induced lipid peroxidation compared to BPE. FPE (162.61 mg GAE/g) had higher total phenol content than BPE. However, BPE (18.65 mg QE/g) had significantly higher total flavonoid content than FPE (13.32 mg QE/g). Phenolic acids (such as gallic acid, catechin, chlorogenic, caffeic, ellagic, p-Coumaric acids) and flavonoids (catechins, rutin and quercetin) were present in both extracts. This study revealed that the enzymes' inhibitory activities and antioxidant potentials of phenolic-rich extracts from C. volubile could be part of the mechanism of actions behind its use for memory/cognitive function as obtained in folklore. However, FPE exhibited significantly higher enzymes, inhibitory and antioxidant potentials than BPE.

KEYWORDS:

• Clerodendrum volubile
• cholinesterase
• monoamine oxidase
• oxidative stress
• polyphenols

Declaration of Interest: The authors report no conflicts of interest. The authors alone are responsible for the content and writing of the article.

ABOUT THE AUTHORS

Ganiyu Oboh is Professor of Biochemistry at the Department of Biochemistry, Federal University of Technology Akure. He is the Principal Investigator of the Functional Foods and Nutraceutical Unit at the Department of Biochemistry, Federal University of Technology Akure. His research interests are in functional foods and nutraceuticals. Omodesola O. Ogunruku is Lecturer at the Department of Biochemistry, Obafemi Awolowo University, Ile-Ife, Nigeria. Her research interests are in functional foods and nutraceuticals. Sunday I. Oyeleye is Lecturer at the Biomedical Technology Department Federal University of Technology Akure. His research interests are in functional foods and nutraceuticals. Tosin A. Olasehinde is Research Scientist at the Nutrition and Toxicology Division, Food Technology Department, Federal Institute of Industrial Research Oshodi, Lagos, Nigeria. He is also a Doctoral Student at the University of FortHare Alice South Africa. His research interests are in functional foods and nutraceuticals. Ayokunle O. Ademosun is Lecturer at the Department of Biochemistry, Federal University of Technology Akure, Ondo State, Nigeria. He is a member of the Functional Foods and Nutraceutical Unit, Department of Biochemistry, Federal University of Technology. His research interests are in functional foods and nutraceuticals. Aline Augusti Boligon is a member of the Phytochemical Research Laboratory, Department of Industrial Pharmacy, Federal University of Santa Maria, Brazil.