Solanum leaves extracts exhibit antioxidant properties and inhibit monoamine oxidase and acetylcholinesterase activities (in vitro) in Drosophila melanogaster

Curcumin improves the ability of donepezil to ameliorate memory impairment in Drosophila melanogaster: involvement of cholinergic and cnc/Nrf2-redox systems

One of the well-established models for examining neurodegeneration and neurotoxicity is the Drosophila melanogaster model of aluminum-induced toxicity. Anti-cholinesterase drugs have been combined with other neuroprotective agents to improve Alzheimer's disease management, but there is not much information on the combination of anti-cholinesterases with dietary polyphenols to combat memory impairment. Here, we assess how curcumin influences some of the critical therapeutic effects of donepezil (a cholinesterase inhibitor) in AlCl3-treated Drosophila melanogaster. Harwich strain flies were exposed to 40 mM AlCl3 - alone or in combination with curcumin (1 mg/g) and/or donepezil (12.5 µg/g and 25 µg/g) - for seven days. The flies' behavioral evaluations (memory index and locomotor performance) were analyzed. Thereafter, the flies were processed into homogenates for the quantification of acetylcholinesterase (AChE), catalase, total thiol, and rate of lipid peroxidation, as well as the mRNA levels of acetylcholinesterase (ACE1) and cnc/NRF2. Results showed that AlCl3-treated flies presented impaired memory and increased activities of acetylcholinesterase and lipid peroxidation, while there were decrease in total thiol levels and catalase activity when compared to the control. Also, the expression of ACE1 was significantly increased while that of cnc/NRF2 was significantly decreased. However, combinations of curcumin and donepezil, especially at lower dose of donepezil, significantly improved the memory index and biochemical parameters compared to donepezil alone. Thus, curcumin plus donepezil offers unique therapeutic effects during memory impairment in the D. melanogaster model of neurotoxicity.

Phytochemicals from African eggplants (Solanum macrocarpon L) and Black nightshade (Solanum nigrum L) leaves as acetylcholinesterase inhibitors: an in-silico study

Acetylcholinesterase inhibitors (AChEIs) like donepezil are commonly used to treat Alzheimer's disease. AChEIs have also been considered for other therapeutic uses, such as anti-inflammatory neuroprotective agents. Consequently, the use of natural plant products as potential AChEIs can have therapeutic benefits. We previously reported the anticholinesterase properties of the phenolics and alkaloids found in the leaf extracts of two tropical plants with nutritional and ethnobotanical importance-African eggplant (Solanum macrocarpon L) and Black nightshade (Solanum nigrum L). Here, we tested the ability of both extracts to inhibit human erythrocyte AChE (an indirect mediator of pro-inflammatory cytokines production via acetylcholine degradation). We further used molecular docking and MD simulation to identify the potential molecular mechanism(s) of phenolic and alkaloid compounds as human AChEIs. Special focus was given to compounds containing the benzyl group that can establish stacking interactions similar to donepezil (a standard AChEI). Flavone-luteolin rutinosides (LR) were identified as single-binding or dual-binding AChEIs; specifically, we attributed the dual-binding LR4 and LR5 to their linked hexose moiety. This characteristic allows the dual binders to occupy the catalytic triads and the peripheral anionic subsite, while exploring the catalytic gorge. We further delineated the inhibition of human erythrocyte AChE, as the flavone common to both plant extracts-luteolin rutinosides-had positive in silico interactions with AChE. These findings suggest that phytochemicals from S. macrocarpon and S. nigrum with dual binding properties can be potential AChE inhibitors. In fact, compounds such as LR4 and LR5 should be further investigated as potential inhibitors of human AChE and may represent important natural alternatives to donepezil.Communicated by Ramaswamy H. Sarma.

Neuroprotective properties of Solanum leaves in Transgenic Drosophila melanogaster model of Alzheimer's disease

INTRODUCTION

We investigated the effect of African eggplant (AE) (Solanum macrocarpon L) and Black nightshade (BN) (Solanum nigrum L) leaves; two tropical vegetables consumed by humans on behavioral, biochemical and histological indices in Drosophila melanogaster model of Alzheimer's disease (AD).

MATERIALS AND METHOD

Transgenic flies expressing human Amyloid Precursor Protein (hAPP) and β-secretase (hBACE 1) were exposed to the pulverized leaf samples (0.1 and 1.0%) in their diets for fourteen days. Thereafter, the flies were assessed for their behavioral indices and routine histology of brain cells. Furthermore, fly head homogenates were assayed for β-amyloid level, activities of acetylcholinesterase (AChE) and β-secretase (BACE-1), as well as oxidative stress markers.

RESULTS

Result showed that the significantly lower (p < 0.05) behavioral parameters (survival, locomotor performance and memory index), higher AChE and BACE-1 activities, β-amyloid, ROS and lipid peroxidation levels, as well as reduced antioxidant indices observed in the AD flies, were significantly ameliorated (p < 0.05) in AD flies treated with the leaf samples.

DISCUSSION

This study has showed that leaves of AE and BN ameliorated behavioral and biochemical indices in AD flies via neural enzyme modulatory, and antioxidant mechanisms.

CONCLUSION

Hence, this study further justifies the neuroprotective properties of both AE and BN.

Effect of Solanum vegetables on memory index, redox status, and expressions of critical neural genes in Drosophila melanogaster model of memory impairment

African eggplant (Solanum macrocarpon L) (AE) and Black Nightshade (Solanum nigrum L) (BN) leaves are green leafy vegetables with nutritional and ethnobotanical values. We have previously characterized the vegetables via HPLC/LC-MS to reveal notable phenolic acids, flavonoids and alkaloids. In this present study, we addressed the efficacy of the two vegetables in mitigating mercuric chloride (HgCl₂)-induced neurotoxicity and memory impairment in Drosophila melanogaster. Flies were exposed to HgCl₂ (0.30 mg/g) alone or in combination with the vegetables (0.1 and 1.0%) of both samples in their diets for seven days. The results showed that HgCl₂ (Hg)-exposed flies had significantly reduced survival rate and memory index, which were ameliorated in the Hg-exposed flies fed AE or BN. This was accompanied by increased reactive oxygen species (ROS) levels, reduced total thiol, as well as catalase, glutathione transferase (GST) and acetylcholine esterase (AChE) activities in Hg-exposed fly heads, but ameliorated in Hg-exposed flies fed dietary inclusions of the vegetables. In addition, the Hg-induced alterations in SOD, NF-ҝB/Relish, Dronc and Reaper mRNA levels were statistically indistinguishable from controls in Hg-treated flies fed diets containing AE or BN. Normalization of cnc/Nrf2 and FOXO were observed only in Hg-treated flies fed BN. These findings suggest that dietary AE or BN leaves offer protection against Hg-induced memory impairment and neurotoxicity in D. melanogaster, and further justify them as functional foods with neuroprotective properties.

Anticholinesterase activity and antioxidant properties of Heinsia crinita and Pterocarpus soyauxii in Drosophila melanogaster model

Background

Plant alkaloids have become important sources of nutraceuticals owing to their pharmacological importance especially in the management of neurodegenerative diseases such as Alzheimer’s disease. In assessing the therapeutic potentials of plant phytochemicals, the fruit fly (Drosophila melanogaster) has emerged as a very veritable tool and has been largely accepted as an alternative model in biomedical research.

Objectives

In this study, alkaloid extracts from bush apple (Heinsia crinita (Afzel.) G. Taylor and padauk (Pterocarpus soyauxii Taub.) leaves were assessed on D. melanogaster exposed to aluminum toxicity.

Materials and methods

Alkaloid extracts were prepared by solvent extraction method. Thereafter, the extracts were evaluated for their in vitro antioxidant properties, Fe²⁺-chelating abilities and inhibitory effects on drosophila acetylcholinesterase (AChE) activity. The samples were also characterized for their constituent alkaloids via HPLC. Thereafter, effective safe dose of the extracts were determined in D. melanogaster (Harwich strain). Subsequently, flies assaulted with AlCl₃ were co-treated with the extracts (8.3 and 16.6 μg/g) for seven days, during which their survival rate was monitored. This was followed by assaying for the activities of AChE, antioxidant enzymes [superoxide dismutase (SOD), catalase and glutathione-S-transferase (GST)]. Also, the flies were assayed for levels of thiobarbituric acid reaction substance (TBARS) and reactive oxygen species (ROS).

Results

The results revealed that both extracts showed in vitro antioxidant properties with Padauk showing significantly higher antioxidant properties in vitro. However, there was no significant difference in their in vitro AChE inhibition. In vivo, Al-induced toxicity reduced survival rate, elevated AChE, SOD and GST activities, as well as TBARS and ROS levels which were ameliorated by the extracts. It was also revealed that piperine was predominant in PA, while 1-cyclohexen-1-yl-pyrrolidine was predominant in BA.

Conclusion

Our data suggest that the protective abilities of these extracts against Al-induced toxicity can be primarily associated with their anticholinesterase and metal chelating abilities. Thus, these vegetables can be potential sources of nutraceuticals against aluminum toxicity and associated diseases.

Solanum vegetable-based diets improve impairments in memory, redox imbalance, and altered critical enzyme activities in Drosophila melanogaster model of neurodegeneration

The effects of two Solanum vegetables, S. macrocarpon L. (African eggplant), and S. nigrum L. (black nightshade) on aluminum model of neurodegeneration in Drosophila melanogaster was investigated. Flies were treated with AlCl₃ alone or in combination with the leaves from both samples in their diets for 7 days. Thereafter, locomotor performance and aversive phototaxic suppression test for learning and memory were carried out. This was followed by assay for reactive oxygen species, antioxidant properties, and enzyme (monoamine oxidase and cholinesterase) activities. Also, the in vitro antioxidant properties and chromatographic phenolic and alkaloid characterization of the samples were determined. Results showed that impaired behavioral physiology, antioxidant status, and enzyme activities observed in Al-treated flies were ameliorated in flies treated with both samples. In addition, both samples exhibited in vitro antioxidant effects. The protective effects from these samples against Al-induced toxicity can be associated with their antioxidant, antimonoaminergic, and anticholinergic properties. PRACTICAL APPLICATIONS: In the quest for a holistic prevention/management approach to neurodegenerative diseases, functional foods are becoming prominent. The use of Drosophila melanogaster to study human diseases is gaining huge recognition due to the high homologue between disease-causing genes between the two organisms. Consequently, this study presents African eggplant and black nightshade leafy vegetables as sources of polyphenols and alkaloids which are able to ameliorate impaired learning and memory, redox status, and enzyme activities in Al-induced D. melanogaster model of neurodegeneration.