Analytical Profiling and Neuroactivity of M. tortuosum via UPLC-MS in Parkinson’s Model

Researchers at Tshwane University of Technology (Pretoria, South Africa) investigated the potential of M. tortuosum extracts and the M. tortuosum extract Zembrin, to alleviate Parkinson’s disease (PD) deficits in zebrafish larvae. Their research assessed locomotion, reactive oxygen species, and total glutathione content. These deficits were induced by theneurotoxin, 6-hydroxydopamine (6-OHDA). Mesembrine alkaloid profiles of a methanol and acid-base extract of M. tortuosum and Zembrin were obtained using ultra-performance liquid chromatography coupled to mass spectrometry (UPLC-MS). A paper based on their work was published in the Journal of Ethnopharmacology (1).

A progressive neurodegenerative disease characterized by classical motor symptoms, including, but not limited to, tremors and rigidity, non-motor symptoms of PD include loss of cognitive function, depression and anxiety; these latter symptoms can develop decades before the motor symptoms become noticeable (2,3). While PD stems from a progressive loss of dopaminergic neurons in the substantia nigra pars compacta (SNpc) of the midbrain region, the cause of this loss is unknown (4,5).

Mesembryanthemum tortuosum (L.) N.E.Brown is an indigenous South African plant that has a varied medicinal profile created through centuries of traditional use (6). Fermented M. tortuosum, known as kougoed has been traditionally chewed, smoked or inhaled as snuff by the Khoisan people of southern Africa for its psychoactive properties (7), and studies have previously confirmed its use as a sedative, anxiolytic and antidepressant herbal remedy (6). Recently, it has been confirmed that M. tortuosum acts as a neurotransmitter-releasing agent (8), as well as displaying both antioxidant and anti-inflammatory properties, which could be beneficial in the treatment of PD (9).

A commercially available standardized M. tortuosum extract with a defined alkaloid composition, Zembrin is an aqueous ethanolic extract prepared in 30% distilled water and 70% ethanol, with a total alkaloid content greater than 0.38% (10).

The larvae of zebrafish (Danio rerio) have gained attention as a model for biomedical research, as the species share 80% genetic homology with humans (11). In addition, zebrafish are smaller in size compared to rodent models, have a high level of reproduction, faster development, and a shorter life cycle, which make the species an economical and robust high throughput screening animal model for drugs of plant origin, particularly complementary for PD experimentation, as zebrafish show early development of the dopaminergic cell networks (12).

Prior to UPLC-MS analysis, the dried M. tortuosum extracts and commercial Zembrin powder (were dissolved in methanol to a final concentration of 1 mg/mL, filtered through 0.2 μm syringe filters, and injected into an ultra-performance liquid chromatography system, with analysis performed using the previously developed method by the researchers (13). In the neuroprotection assay, zebrafish larvae at two days post-fertilization were treated concurrently with 6-OHDA (250.0 μM) and M. tortuosum extracts or Zembrin, and incubated for 72 h. At the end of the incubation period, locomotion was monitored and the reactive oxygen species (ROS) and total glutathione content (tGSH) in the larvae were also assessed. In the neurorestoration assay, the 2 dpf larvae were initially pre-treated with 6-OHDA (250.0 μM) for 24 h, and the extracts or Zembrin were added after 24 h and incubation proceeded for a further 48 h. Locomotion, reactive oxygen species (ROS), and total glutathione content (tGSH) were determined at the end of the 48 hour incubation. Both assays utilized L-dopa and selegiline as the positive controls.

The researchers determined that the M. tortuosum extracts and Zembrin containing various levels of mesembrine alkaloids improved both locomotion and oxidative stress associated with PD in the zebrafish larvae model. Furthermore, the effects of L-dopa and selegiline as core treatments in the management of PD were further confirmed in this PD zebrafish larvae model. However, they stressed that, while the zebrafish larvae model provide valuable insights into biological effects, direct extrapolation to humans is limited and the results must be validated in higher vertebrate models (1).

References

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