Potential of South African medicinal plants targeting the reduction of Aβ42 protein as a treatment of Alzheimer's disease

Oxymatrine-mediated prevention of amyloid β-peptide-induced apoptosis on Alzheimer's model PC12 cells: in vitro cell culture studies and in vivo cognitive assessment in rats

Alzheimer's disease (AD) is a major neurological disease affecting elderly individuals worldwide. Existing drugs only reduce the symptoms of the disease without addressing the underlying causes. Commonly, Aβ25-35 peptide aggregation is the main reason for AD development. Recently, the discovery of multiple protein-targeting molecules has provided a new strategy for treating AD. This study demonstrates the neuroprotective potential of oxymatrine against multiple mechanisms, such as acetylcholinesterase, mitochondrial damage, and β-amyloid-induced cell toxicity. The in vitro cell culture studies showed that oxymatrine possesses significant potential to inhibit acetylcholine esterase and promotes antioxidant, antiapoptotic effects while preventing Aβ25-35 peptide aggregation in PC12 cells. Furthermore, oxymatrine protects PC12 cells against Aβ25-35-induced cytotoxicity and down-regulates the reactive oxygen species generation. The in vivo acute toxicological studies confirm the safety of oxymatrine without causing organ damage or death in animals. Overall, this study provided evidence that oxymatrine is an efficient neuroprotective agent, with a potential to be a multifunctional drug for Alzheimer's disease treatment. These findings present a reliable and synergistic approach for treating AD.

In-silico and in-vitro assessments of some fabaceae, rhamnaceae, apocynaceae, and anacardiaceae species against Mycobacterium tuberculosis H37Rv and triple-negative breast cancer cells

Medicinal plants play a huge role in the treatment of various diseases in the Limpopo province (South Africa). Traditionally, concoctions used for treating tuberculosis and cancer are sometimes prepared from plant parts naturally occurring in the region, these include (but not limited to) Schotia brachypetala, Rauvolfia caffra, Schinus molle, Ziziphus mucronate, and Senna petersiana. In this study, the aim was to evaluate the potential antimycobacterial activity of the five medicinal plants against Mycobacterium smegmatis mc²155, Mycobacterium aurum A + , and Mycobacterium tuberculosis H37Rv, and cytotoxic activity against MDA-MB 231 triple-negative breast cancer cells. Phytochemical constituents present in R. caffra and S. molle were tentatively identified by LC-QTOF-MS/MS as these extracts showed antimycobacterial and cytotoxic activity. A rigorous Virtual Screening Workflow (VSW) of the tentatively identified phytocompounds was then employed to identify potential inhibitor/s of M. tuberculosis pantothenate kinase (PanK). Molecular dynamics simulations and post-MM-GBSA free energy calculations were used to determine the potential mode of action and selectivity of selected phytocompounds. The results showed that plant crude extracts generally exhibited poor antimycobacterial activity, except for R. caffra and S. molle which exhibited average efficacy against M. tuberculosis H37Rv with minimum inhibitory concentrations between 0.25-0.125 mg/mL. Only one compound with a favourable ADME profile, namely, norajmaline was returned from the VSW. Norajmaline exhibited a docking score of -7.47 kcal/mol, while, pre-MM-GBSA calculation revealed binding free energy to be -37.64 kcal/mol. All plant extracts exhibited a 50% inhibitory concentration (IC₅₀) of < 30 μg/mL against MDA-MB 231 cells. Flow cytometry analysis of treated MDA-MB 231 cells showed that the dichloromethane extracts from S. petersiana, Z. mucronate, and ethyl acetate extracts from R. caffra and S. molle induced higher levels of apoptosis than cisplatin. It was concluded that norajmaline could emerge as a potential antimycobacterial lead compound. Validation of the antimycobacterial activity of norajmaline will need to be performed in vitro and in vivo before chemical modifications to enhance potency and efficacy are done. S. petersiana, Z. mucronate, R.caffra and S. molle possess strong potential as key contributors in developing new and effective treatments for triple-negative breast cancer in light of the urgent requirement for innovative therapeutic solutions.

Molecular Integrative Analysis of the Inhibitory Effects of Dipeptides on Amyloid β Peptide 1-42 Polymerization

The major pathological feature of Alzheimer's disease (AD) is the aggregation of amyloid β peptide (Aβ) in the brain. Inhibition of Aβ₄₂ aggregation may prevent the advancement of AD. This study employed molecular dynamics, molecular docking, electron microscopy, circular dichroism, staining of aggregated Aβ with ThT, cell viability, and flow cytometry for the detection of reactive oxygen species (ROS) and apoptosis. Aβ₄₂ polymerizes into fibrils due to hydrophobic interactions to minimize free energy, adopting a β-strand structure and forming three hydrophobic areas. Eight dipeptides were screened by molecular docking from a structural database of 20 L-α-amino acids, and the docking was validated by molecular dynamics (MD) analysis of binding stability and interaction potential energy. Among the dipeptides, arginine dipeptide (RR) inhibited Aβ₄₂ aggregation the most. The ThT assay and EM revealed that RR reduced Aβ₄₂ aggregation, whereas the circular dichroism spectroscopy analysis showed a 62.8% decrease in β-sheet conformation and a 39.3% increase in random coiling of Aβ₄₂ in the presence of RR. RR also significantly reduced the toxicity of Aβ₄₂ secreted by SH-SY5Y cells, including cell death, ROS production, and apoptosis. The formation of three hydrophobic regions and polymerization of Aβ₄₂ reduced the Gibbs free energy, and RR was the most effective dipeptide at interfering with polymerization.

Dementia in Africa: Current evidence, knowledge gaps, and future directions

In tandem with the ever-increasing aging population in low and middle-income countries, the burden of dementia is rising on the African continent. Dementia prevalence varies from 2.3% to 20.0% and incidence rates are 13.3 per 1000 person-years with increasing mortality in parts of rapidly transforming Africa. Differences in nutrition, cardiovascular factors, comorbidities, infections, mortality, and detection likely contribute to lower incidence. Alzheimer's disease, vascular dementia, and human immunodeficiency virus/acquired immunodeficiency syndrome-associated neurocognitive disorders are the most common dementia subtypes. Comprehensive longitudinal studies with robust methodology and regional coverage would provide more reliable information. The apolipoprotein E (APOE) ε4 allele is most studied but has shown differential effects within African ancestry compared to Caucasian. More candidate gene and genome-wide association studies are needed to relate to dementia phenotypes. Validated culture-sensitive cognitive tools not influenced by education and language differences are critically needed for implementation across multidisciplinary groupings such as the proposed African Dementia Consortium.

Potential of Sorghum Polyphenols to Prevent and Treat Alzheimer's Disease: A Review Article

Alzheimer's disease (AD) is characterized by the excessive deposition of extracellular amyloid-beta peptide (Aβ) and the build-up of intracellular neurofibrillary tangles containing hyperphosphorylated tau proteins. This leads to neuronal damage, cell death and consequently results in memory and learning impairments leading to dementia. Although the exact cause of AD is not yet clear, numerous studies indicate that oxidative stress, inflammation, and mitochondrial dysfunction significantly contribute to its onset and progression. There is no effective therapeutic approach to stop the progression of AD and its associated symptoms. Thus, early intervention, preferably, pre-clinically when the brain is not significantly affected, is a better option for effective treatment. Natural polyphenols (PP) target multiple AD-related pathways such as protecting the brain from Aβ and tau neurotoxicity, ameliorating oxidative damage and mitochondrial dysfunction. Among natural products, the cereal crop sorghum has some unique features. It is one of the major global grain crops but in the developed world, it is primarily used as feed for farm animals. A broad range of PP, including phenolic acids, flavonoids, and condensed tannins are present in sorghum grain including some classes such as proanthocyanidins that are rarely found in others plants. Pigmented varieties of sorghum have the highest polyphenolic content and antioxidant activity which potentially makes their consumption beneficial for human health through different pathways such as oxidative stress reduction and thus the prevention and treatment of neurodegenerative diseases. This review summarizes the potential of sorghum PP to beneficially affect the neuropathology of AD.

A Novel Cardenolide Glycoside Isolated from Xysmalobium undulatum Reduces Levels of the Alzheimer's Disease-Associated β-Amyloid Peptides Aβ42 In Vitro

Elevated levels of the amylo β-proteins (Aβ), particularly Aβ42, are associated with a high risk of Alzheimer’s disease (AD). The Aβ proteins are produced from cellular processing of the amyloid precursor proteins (APPs). To identify natural products that block the formation of Aβ-proteins from APPs, we previously screened a library of plant extracts and identified Xysmalobium undulaum (Apocynaceae) as a potential plant for further research. Here, we provide a report on the isolation and identification of the active principles from the plant species using a bioassay-guided fractionation. Fractions and resulting pure compounds from the purification process of the extract of X. undulatum were screened in vitro against APPs transfected HeLa cell lines. Three compounds, acetylated glycosydated crotoxogenin (1), xysmalogenin-3, β-d-glucopyranoside (2), and crotoxigenin 3-O-glucopyranoside (3), were subsequently isolated and their structures elucidated using NMR and mass spectrometry. Compound 1, a novel cardenolide, and 2 significantly decreased the Aβ42 levels in a dose-dependent manner while compound 3 was inactive. In silico investigations identified the AD’s β-secretase enzyme, BACE1, as a potential target for these compounds with the glycoside moiety being of significance in binding to the enzyme active site. Our study provides the first report of a novel cardenolide and the potential of cardenolides as chemical scaffolds for developing AD treatment drugs.

The relationship between Indigenous and allopathic health practitioners in Africa and its implications for collaboration: a qualitative synthesis

BACKGROUND

There have been increasing calls for collaboration between Indigenous health practitioners (IHPs) and allopathic health practitioners (AHPs) in Africa. Despite this, very few successful systems exist to facilitate formal collaboration. Direct relationships between providers, and at a health systems level are crucial to successful collaboration, but the nature and extent of these relationships have yet to be adequately explored.

OBJECTIVE

To explore the relationship between IHPs and AHPs in Africa, and to discuss the implications of this for future collaboration.

METHODS

An interpretive qualitative synthesis approach, combining elements of thematic analysis, meta-ethnography, and grounded theory, was used to systematically bring together findings of qualitative studies addressing the topic of collaboration between Indigenous and allopathic health practitioners in Africa.

RESULTS

A total of 1,765 papers were initially identified, 1,748 were excluded after abstract, full text and duplicate screening. Five additional studies were identified through references. Thus, 22 papers were included in the final analysis. We found that the relationship between Indigenous and allopathic health practitioners is defined by a power struggle which gives rise to lack of mutual understanding, rivalry, distrust, and disrespect.

CONCLUSION

The power struggle which defines the relationship between IHPs and AHPs in Africa is a hindrance to their collaboration and as such could partly account for the limited success of efforts to foster collaboration to date. Future efforts to foster collaboration between IHPs and AHPs in Africa must aim to balance the power disparity between them if collaboration is to be successful. Since this would be a novel approach, decision-makers and organisations who trial this power balancing approach to facilitate collaboration should evaluate resultant policies and interventions to ascertain their feasibility and efficacy in fostering collaboration, and the lessons learnt should be shared.

Ethnobotany, phytochemistry and pharmacological significance of the genus Bulbine (Asphodelaceae)

ETHNOPHARMACOLOGICAL RELEVANCE

The genus Bulbine (Asphodelaceae) is spread across Southern Africa and Australia and has been traditionally used for various medicinal applications such as treating skin diseases, burns, diarrhoea, and sexually transmitted diseases.

AIM OF THIS REVIEW

The aim is to present a critical review of the ethnomedicinally important species of the genus Bulbine with a comprehensive overview of their chemical constituents and biological activities.

MATERIALS AND METHODS

This paper is an overview of literature published on the genus Bulbine in the last six decades with regards to phytochemical composition and their respective pharmacological potentials with the aid of data obtained from the search engine Google Scholar with string searches performed using keywords to obtain relevant publications from scientific databases including ACS Journals, PubMed, Science Direct, SciELO, Sci Finder, Springer, Tailor & Francis, The Plant List Database, Web of Science and Wiley.

RESULTS

The literature survey reveals that only 12 species in the genus Bulbine have been reported to be used traditionally with scientific records of ethnomedicinal usage Anthraquinones appeared as the most abundant phytochemicals in the genus. Other isolated/detected metabolites include isofuranonaphthoquinones, flavonoids, and triterpenoids. Promising pharmacological activities have been reported by members of the genus with antiplasmodial, antitrypanosomal, antiviral, antioxidant, anticancer, anti-inflammatory and anti-microbial activity, potent wound healing properties as well as improved reproduction.

CONCLUSIONS

This review showed the traditional uses of this genus and its preventative and curative properties in the management of the listed diseases providing support from bioassays of the tested compounds and extracts. State-of-the-art analytical techniques are required for the characterisation and quantification of the compounds within the genus. The efficacy of the therapeutic potential of the Bulbine species need to be further confirmed with pre-clinical and clinical studies.