Chemical composition and studying the possible neuroprotective effect of iridoids-rich fraction from Pentas lanceolata leaves using rotenone model of Parkinson's disease in mice

Abstract

Parkinsonism is an age-related neurodegenerative illness that affects motor coordination leading to loss of dopaminergic neurons. Many medications are used for the treatment of Parkinson's disease but are only symptomatic and have a limited effect on the progression of this ailment. Therefore, bioactive compounds which derived from plants have been examined for their ability to improve the neuronal damage and cell death happened in parkinsonian patients. In this study the iridoids-rich fraction isolated from Pentas lanceolata (PIRF) leaves was investigated for its phytoconstituents. Seven iridoids (1-7) and one flavonol diglycoside (8) were isolated, and their chemical structures were achieved by ¹H and ¹³C nuclear magnetic resonance and ESI-MS spectral data. Compound 1 (6β,7β-epoxy-8-epi-splendoside) and 5 (gaertneroside) were isolated for the first time from Pentas genus as well as compound 8 (kaempferol-3-O-robinobioside). The current study aims to investigate the possible anti-parkinsonian effect of PIRF using a rotenone model of Parkinsonism in mice. Behavioural tests (wirehanging, stair and wooden-walking tests) were done to examine the motor coordination in mice after treatment. Biochemical and histopathological examinations for brain striatum in different groups were also evaluated. Results revealed that rotenone-treated mice had poor motor functions described by depletion of dopamine and Ach levels, a significant increase in proinflammatory cytokines, IL-1B, TNF-α and Mcp-1 and oxidative biomarkers with subsequent reduction in antioxidant mediators. Disorganization of striatum, degenerated neurocytes, slight vacuolation, shrunken neurons with pyknotic nuclei and apoptotic cells are displayed by histopathological examinations. Treatment with PIRF ameliorates the neurodegeneration-induced by rotenone in the brain of mice. The anti-parkinsonian effect of PIRF could be attributed to their bioactive constituents of iridoids.

Keywords: Pentas lanceolata; Behavioral tests Rotenone; Motor functions; Parkinson's disease; Plant iridoids.

Fig. 1

Design of extraction and isolation of compounds of iridoids-rich fraction from Pentas lanceolata  leaves (PIRF)

Fig. 2

Experimental design of in vitro and in vivo anti-parkinsonian study. DMSO, Dimethylsulfoxide, PIRF, The iridoids-rich fraction isolated from Pentas lanceolata leaves, Rot, Rotenone

Fig. 3

Chemical structures of isolated compounds 1–8 from Pentas lanceolata iridoids-rich fraction

Fig. 4

The expression of BDNF gene in human colonic epithelial cell line (Caco-2)

Fig. 5

The expression of NGF gene in human astrocytoma cell (1321N1)

Fig. 6

Effect of PIRF treatment in rotenone model of Parkinsonism on behavioral tests. A, In the wire-hanging test. B, In the stair test. C, In the wooden-walking test. *, means significantly different from control group; @, significantly different from rotenone group. Each value represents the mean of 11 measurements ± standard error of mean (SEM)

Fig. 7

Effect of PIRF treatment in rotenone model of Parkinsonism on dopamine level. *, means significantly different from control group. Each value represents the mean of 8 values ± standard error of mean (SEM)

Fig. 8

Effect of PIRF treatment in rotenone model of Parkinsonism on inflammatory markers. A on IL-1β content, B on TNF- α content, and C on monocyte chemotactic protein-1 content. *, significantly different from control group. Each value represents the mean of 8 values ± standard error of mean (SEM)

Fig. 9

Effect of PIRF treatment in rotenone model of Parkinsonism on acetylcholine esterase level. *, significantly different from control group. Each value represents the mean of 8 values ± standard error of mean (SEM)

Fig. 10

Effect of PIRF treatment in rotenone model of Parkinsonism on β- amyloid content. *, significantly different from control group. Each value represents the mean of 8 values ± standard error of mean (SEM)

Fig. 11

Effect of PIRF treatment in rotenone model of Parkinsonism of oxidative markers. A on MDA brain content, B on GSH brain content, and C on NO content. *, significantly different from control group. @, significantly different from rotenone group. Each value represents the mean of 8 values ± standard error of mean (SEM)

Fig. 12

A photomicrograph of brain. A control group shows normal histological structure brain tissue with normal neurons (N), B rotenone treated group shows disorganization of striatum, degenerated neurocytes with dilated blood vessels (Bv), vacuolation (V) pyknotic nuclei (P), apoptotic cells (Ap), (C): rotenone and reference L-dopa treated group shows moderate improvement with perivascular vacuolation (V), pyknotic nuclei (P), apoptotic cells (Ap) and slight with dilated blood vessels (Bv), (D): rotenone and low dose PIRF treated group shows moderate improvement was seen with slight perivascular vacuolation (V), pyknotic nuclei (P), apoptotic cells (Ap) and slight with dilated blood vessels (arrowhead), (E): rotenone and high dose PIRF treated group shows noticeable improvement was seen in almost neuronal cells of striatum, with few histopathological changes such as minimal pyknotic nuclei (P), apoptotic cells (Ap) and normal dilated blood vessels (Bv)