Urbanization and industrialization are responsible for environmental contamination in the air, water, and soil. These activities also generate large amounts of heavy metal ions in the environment, and these contaminants cause various types of health issues in humans and other animals. Hexavalent chromium, lead, and cadmium are toxic heavy metal ions that come into the environment through several industrial processes, such as tanning, electroplating, coal mining, agricultural activities, the steel industry, and chrome plating. Several physical and chemical methods are generally used for the heavy metal decontamination of wastewater. These methods have some disadvantages, including the generation of secondary toxic sludge and high operational costs. Hence, there is a need to develop a cost-effective and eco-friendly method for the removal of heavy metal ions from polluted areas. Biological methods are generally considered eco-friendly and cost-effective. This review focuses on heavy metal contamination, its toxicity, and eco-friendly approaches for the removal of heavy metals from contaminated sites.

Berberine (a protoberberine isoquinoline alkaloid) has shown promising pharmacological activities, including analgesic, anti-inflammatory, anticancer, antidiabetic, anti-hyperlipidemic, cardioprotective, memory enhancement, antidepressant, antioxidant, anti-nociceptive, antimicrobial, anti- HIV and cholesterol-lowering effects. It is used in the treatment of the neurodegenerative disorder. It has strong evidence to serve as a potent phytoconstituent in the treatment of various neurodegenerative disorders such as AD. It limits the extracellular amyloid plaques and intracellular neurofibrillary tangles. It has also lipid-glucose lowering ability, hence can be used as a protective agent in atherosclerosis and AD. However, more detailed investigations along with safety assessment of berberine are warranted to clarify its role in limiting various risk factors and AD-related pathologies. This review highlights the pharmacological basis to control oxidative stress, neuroinflammation and protective effect of berberine in AD, which will benefit to the biological scientists in understanding and exploring the new vistas of berberine in combating Alzheimer’s disease.

Since primitive times, herbs have been extensively used in conventional remedies for boosting cognitive impairment and age-associated memory loss. It is mentioned that medicinal plants have a variety of dynamic components, and they have become a prominent choice for synthetic medications for the care of cognitive and associated disorders. Herbal remedies have played a major role in the progression of medicine, and many advanced drugs have already been developed. Many studies have endorsed practicing herbal remedies with phytoconstituents, for healing Alzheimer’s disease (AD). All the information in this article was collated from selected research papers from online scientific databases, such as PubMed, Web of Science, and Scopus. The aim of this article is to convey the potential of herbal remedies for the prospect management of Alzheimer’s and related diseases. Herbal remedies may be useful in the discovery and advancement of drugs, thus extending new leads for neurodegenerative diseases such as AD. Nanocarriers play a significant role in delivering herbal medicaments to a specific target. Therefore, many drugs have been described for the management of age-linked complaints such as dementia, AD, and the like. Several phytochemicals are capable of managing AD, but their therapeutic claims are restricted due to their lower solubility and metabolism. These limitations of natural therapeutics can be overcome by using a targeted nanocarrier system. This article will provide the primitive remedies as well as the development of herbal remedies for AD management.

Severe acute respiratory syndrome coronavirus 2 (SARS‐CoV‐2) is a human coronavirus (HCoV) that has created a pandemic situation worldwide as COVID‐19. This virus can invade human cells via angiotensin‐converting enzyme 2 (ACE2) receptor‐based mechanisms, affecting the human respiratory tract. However, several reports of neurological symptoms suggest a neuroinvasive development of coronavirus. SARS‐CoV‐2 can damage the brain via several routes, along with direct neural cell infection with the coronavirus. The chronic inflammatory reactions surge the brain with proinflammatory elements, damaging the neural cells, causing brain ischemia associated with other health issues. SARS‐CoV‐2 exhibited neuropsychiatric and neurological manifestations, including cognitive impairment, depression, dizziness, delirium, and disturbed sleep. These symptoms show nervous tissue damage that enhances the occurrence of neurodegenerative disorders and aids dementia. SARS‐CoV‐2 has been seen in brain necropsy and isolated from the cerebrospinal fluid of COVID‐19 patients. The associated inflammatory reaction in some COVID‐19 patients has increased proinflammatory cytokines, which have been investigated as a prognostic factor. Therefore, the immunogenic changes observed in Parkinson’s and Alzheimer’s patients include their pathogenetic role. Inflammatory events have been an important pathophysiological feature of neurodegenerative diseases (NDs) such as Parkinson’s and Alzheimer’s. The neuroinflammation observed in AD has exacerbated the Aβ burden and tau hyperphosphorylation. The resident microglia and other immune cells are responsible for the enhanced burden of Aβ and subsequently mediate tau phosphorylation and ultimately disease progression. Similarly, neuroinflammation also plays a key role in the progression of PD. Several studies have demonstrated an interplay between neuroinflammation and pathogenic mechanisms of PD. The dynamic proinflammation stage guides the accumulation of α‐synuclein and neurodegenerative progression. Besides, few viruses may have a role as stimulators and generate a cross‐autoimmune response for α‐synuclein. Hence, neurological complications in patients suffering from COVID‐19 cannot be ruled out. In this review article, our primary focus is on discussing the neuroinvasive effect of the SARS‐CoV‐2 virus, its impact on the blood‐brain barrier, and ultimately its impact on the people affected with neurodegenerative disorders such as Parkinson’s and Alzheimer’s.

In neurodegenerative disorders, crossing the blood-brain barrier to achieve higher brain uptake of drugs has attracted considerable interest of researchers in recent years. The present approach is designed with a hypothesis that polyamidoamine (PAMAM) dendrimer can be suitable for better brain delivery of donepezil (DZ) utilizing the conjugation strategy. Amine-terminated 4.0 G PAMAM dendrimers (utilizing ethylenediamine core) were synthesized and characterized by different spectroscopic methods (¹H and ¹³C NMR, UV–vis, Fourier transform infrared, electrospray ionization mass). The synthesized PAMAM dendrimer was then conjugated with DZ-ester and finally DZ (ester)-PAMAM conjugate (PDZ) was prepared. The chemical shifts of −CHO (δ = 9.92) and O–CH₃ (δ = 3.153) in ¹H NMR spectrum confirmed the synthesis of PDZ. The percent drug conjugation of DZ was approximately 26%, and 16 DZ molecules were conjugated with each PAMAM molecule. The size and ζ-potential observed of PDZ conjugate were 122 ± 1.88 nm and 0.434 ± 0.322, respectively. In vitro release studies suggested that DZ release was in a sustained fashion until 120 h at physiological pH conditions. The in vitro acetylcholine esterase (AChE) inhibition activity of PDZ formulation was significantly higher (p < 0.05) than that of the DZ alone at 1 μM dose. In the in vivo studies, the brain uptake of PDZ was quite higher than that of DZ following intravenous administration in Sprague-Dawley rats. The plasma drug concentration studies resulted into improved pharmacokinetic parameters. Half-life (t_1/2), volume of distribution (V_d), and clearance were found to be 5.75 ± 0.41 h^–1, 0.135 ± 0.02 L, and 0.016 ± 0.0021 L/h, respectively, in the case of PDZ formulation and 1.09 ± 0.10 h^–1, 0.172 ± 0.016 L, and 0.108 ± 0.014 L/h, respectively, in the case of DZ solution. The improved half-life and 4-fold increase in brain uptake was observed in the case of the dendrimer-conjugated formulation, which suggested that the synthesized conjugates provide significantly higher DZ brain delivery. The prepared PDZ-conjugated formulation improved AChE inhibition in vitro and the brain delivery in vivo. This strategy may be explored further for better delivery of DZ to the brain.