Bio-Guided Fractionation of Stem Bark Extracts from Phyllanthus muellarianus: Identification of Phytocomponents with Anti-Cholinesterase Activity.

Gabriella Massolini,Manuela Bartolini,Gloria Brusotti,Vincenza Andrisano,Caterina Temporini,Marina Naldi

doi:10.3390/molecules26144376

Gabriella Massolini, Manuela Bartolini

Open Access

https://doi.org/10.3390/molecules26144376

Copy DOI

Abstract

A combination of flash chromatography, solid phase extraction, high-performance liquid chromatography, and in vitro bioassays was used to isolate phytocomponents endowed with anticholinesterase activity in extract from Phyllanthus muellarianus. Phytocomponents responsible for the anti-cholinesterase activity of subfractions PMF1 and PMF4 were identified and re-assayed to confirm their activity. Magnoflorine was identified as an active phytocomponent from PMF1 while nitidine was isolated from PMF4. Magnoflorine was shown to be a selective inhibitor of human butyrylcholinesterase—hBChE (IC50 = 131 ± 9 μM and IC50 = 1120 ± 83 μM, for hBuChE and human acetylcholinesterase—hAChE, respectively), while nitidine showed comparable inhibitory potencies against both enzymes (IC50 = 6.68 ± 0.13 μM and IC50 = 5.31 ± 0.50 μM, for hBChE and hAChE, respectively). When compared with the commercial anti-Alzheimer drug galanthamine, nitidine was as potent as galanthamine against hAChE and one order of magnitude more potent against hBuChE. Furthermore, nitidine also showed significant, although weak, antiaggregating activity towards amyloid-β self-aggregation.

Highlights

Since ancient times, plants have been known as a source of active compounds either with poisoning or therapeutic effects
We report the evaluation of the anticholinesterase activity of extracts from the stem bark of Phyllanthus muellarianus (PM) and the bio-guided fractionation of the most active extract to identify phytocomponents endowed with anticholinesterase activity
Water extracts of the stem bark of PM (PMWE), prepared in accordance with the traditional use, were selected as a potential source of phytocomponents endowed with anticholinesterase activity within a screening campaign on decoctions from eight African plants collected in the camps of Abing (Cameroon) (Table S1, Supplementary Material)

Summary

Introduction

Plants have been known as a source of active compounds either with poisoning or therapeutic effects. An extensive chemical investigation has been carried out along the years by few research groups to validate the traditional use of PM extracts in the treatment of wound infections and as wound-healing lotions [15,17,18,19,20,21,22,23] These investigations have led to the identification of the alkaloid nitidine as the main phytocomponent endowed with antimicrobial activity in the stem bark extracts [18], while geraniin was identified as the major antimicrobial agent in the aqueous extracts from aerial part [20]. The first was published in 2007 by Joshi et al [25], who showed that the aqueous extracts of Phyllanthus amarus leaves and stems could exert antiamnesic activity in mice This effect was correlated to the anticholinesterase, antioxidant, and anti-inflammatory activity of some phytocomponents which, were not identified. For the most interesting phytocomponents, the inhibitory activity toward amyloidbeta (Aβ) self-aggregation, a well-known pathological hallmark of AD and, a widely studied therapeutic target for AD treatment [33], was evaluated

Results and Discussion

Plant Material

Extraction Procedure

Determination of Polyphenol Content

Fractionation of dPMME by Solid Phase Extraction

Fractionation of PMME by Flash Chromatography

Chromatographic Analysis

Isolation of PC1 from F1

Isolation of PC2a and PC2b from Fraction F2

3.10. MS Analysis of Isolated Phytocomponents

3.12. Inhibition of Human Cholinesterase Activity

3.13. Inhibition of Aβ1–42 Self-Aggregation