UPLC-PDA-ESI-QTOF-MS/MS fingerprint of purified flavonoid enriched fraction of Bryophyllum pinnatum; antioxidant properties, anticholinesterase activity and in silico studies

Abstract

Context

Bryophyllum pinnatum (Lam.) Oken (Crassulaceae) is used traditionally to treat many ailments.

Objectives

This study characterizes the constituents of B. pinnatum flavonoid-rich fraction (BPFRF) and investigates their antioxidant and anticholinesterase activity using in vitro and in silico approaches.

Materials and methods

Methanol extract of B. pinnatum leaves was partitioned to yield the ethyl acetate fraction. BPFRF was isolated from the ethyl acetate fraction and purified. The constituent flavonoids were structurally characterized using UPLC-PDA-MS². Antioxidant activity (DPPH), Fe²⁺-induced lipid peroxidation (LP) and anticholinesterase activity (Ellman’s method) of the BPFRF and standards (ascorbic acid and rivastigmine) across a concentration range of 3.125–100 μg/mL were evaluated in vitro for 4 months. Molecular docking was performed to give insight into the binding potentials of BPFRF constituents against acetylcholinesterase (AChE) and butyrylcholinesterase (BuChE).

Results

UPLC-PDA-MS² analysis of BPFRF identified carlinoside, quercetin (most dominant), luteolin, isorhamnetin, luteolin-7-glucoside. Carlinoside was first reported in this plant. BPFRF significantly inhibited DPPH radical (IC₅₀ = 7.382 ± 0.79 µg/mL) and LP (IC₅₀ = 7.182 ± 0.60 µg/mL) better than quercetin and ascorbic acid. Also, BPFRF exhibited potent inhibition against AChE and BuChE with IC₅₀ values of 22.283 ± 0.27 µg/mL and 33.437 ± 1.46 µg/mL, respectively compared to quercetin and rivastigmine. Docking studies revealed that luteolin-7-glucoside, carlinoside and quercetin interact effectively with crucial amino acid residues of AChE and BuChE through hydrogen bonds.

Discussion and conclusions

BPFRF possesses an excellent natural source of cholinesterase inhibitor and antioxidant. The material could be further explored for the potential treatment of oxidative damage and cholinergic dysfunction in Alzheimer’s disease.

Keywords:

• Alzheimer’s diseases
• acetylcholinesterase
• butyrylcholinesterase
• carlinoside
• docking studies
• lipid peroxidation

Author’s contribution

Authors OFCN, CAA and JOO designed the work; JOO conducted most of the in vitro assay, literature search and prepared the draft manuscript. DEE provided inputs on the antioxidant assay. Author CUI provided insight into the in silico experiment, Author JEP read the manuscript and Authors OFCN, BCN, CAA evaluated and approved the design, and supervised the work. All authors read and approved the final manuscript.

Acknowledgements

The authors hereby acknowledge Dr. Chukwuka Ogbonna for assisting with the sourcing of the plant material. Dr. Malcom J. Taylor of the mass spectrometry unit of the Central Analytical Facility (CAF), Stellenbosch University, South Africa, for assisting with the UPLC-PDA-QTOF-ESI-MS/MS analysis and data interpretation, as well as the members of the Centre for Bio-computing and Drug Design (CBDD), Adekunle Ajasin University, Nigeria, for the inputs on the isolation and purification of the BPFRF.

Disclosure statement

No potential conflict of interest was reported by the author(s).

Data availability statement

The data that support the findings of this study are available from the authors upon request.