Phyto-Carbazole Alkaloids from the Rutaceae Family as Potential Protective Agents against Neurodegenerative Diseases

Role of Calcitriol and Vitamin D Receptor (VDR) Gene Polymorphisms in Alzheimer's Disease

Alzheimer's disease (AD) is characterized by amyloid beta (Aβ) buildup and neuronal degeneration. An association between low serum vitamin D levels and an increased risk of AD has been reported in several epidemiological studies. Calcitriol (1,25-dihydroxycholecalciferol) is the active form of vitamin D, and is generated in the kidney and many other tissues/organs, including the brain. It is a steroid hormone that regulates important functions like calcium/phosphorous levels, bone mineralization, and immunomodulation, indicating its broader systemic significance. In addition, calcitriol confers neuroprotection by mitigating oxidative stress and neuroinflammation, promoting the clearance of Aβ, myelin formation, neurogenesis, neurotransmission, and autophagy. The receptors to which calcitriol binds (vitamin D receptors; VDRs) to exert its effects are distributed over many organs and tissues, representing other significant roles of calcitriol beyond sustaining bone health. The biological effects of calcitriol are manifested through genomic (classical) and non-genomic actions through different pathways. The first is a slow genomic effect involving nuclear VDR directly affecting gene transcription. The association of AD with VDR gene polymorphisms relies on the changes in vitamin D consumption, which lowers VDR expression, protein stability, and binding affinity. It leads to the altered expression of genes involved in the neuroprotective effects of calcitriol. This review summarizes the neuroprotective mechanism of calcitriol and the role of VDR polymorphisms in AD, and might help develop potential therapeutic strategies and markers for AD in the future.

Antitumor and Phytochemical Properties of Ferula assa-foetida L. Oleo-Gum-Resin against HT-29 Colorectal Cancer Cells In Vitro and in a Xenograft Mouse Model

Colorectal cancer (CRC) is one of the most frequently occurring tumors. Ferula assa-foetida oleo-gum-resin (OGR) extract is a traditional cooking spice known for its broad spectrum of biological activities such as antifungal, antiparasitic, and anti-inflammatory activities. This study evaluated the antitumor effect of OGR extract against HT-29 colorectal cancer cells. The OGR chemical composition was analyzed using LC-ESI-MS/MS; MTT, clonogenic assays, and a xenograft model were used to measure cytotoxicity, while apoptotic proteins were detected using Western blotting. Phytochemical analysis revealed that the extract was a rich source of isoflavones, xanthones, and other derivatives. In a dose-dependent manner, the OGR extract significantly inhibited colony formation ability and HT-29 cell growth (IC50 was 3.60 ± 0.02 and 10.5 ± 0.1 mg/mL, respectively). On the other hand, the OGR extract significantly induced apoptosis and increased the expression of some pro-death proteins involved in cellular apoptosis including PUMA, BIM, BIK, and BAK. Moreover, in a subcutaneous HT-29 xenograft model, the tumor volume and burden decreased after treatment with the OGR extract (550 ± 32 mm3 and 16.3 ± 3.6, respectively) This study demonstrated that Ferula assa-foetida OGR ethanolic extract has potential antitumor effects against HT-29 CRC cell lines by reducing cell viability and the function of apoptosis. More studies are needed to reveal the underlying mechanisms related to cytotoxicity and apoptosis induction.

Novel studies on Isolation, purification and characterization of dibenzonitro compound from Glycosmis pentaphylla (Retz.) DC. and effect in downregulating neuronal cancers

To isolate Letrozole from Glycosmis pentaphylla (Retz.) DC. and to determine its effect on regulating the proliferation, cell cycle distribution, apoptosis and key mechanisms in human neuroblastoma cell lines. Letrozole was isolated through column chromatographic technique and its effect was checked on human neuroblastoma cell lines, IMR 32. The effects of Letrozole on cell viability were measured by MTT assay, and the cell cycle distribution was determined by flow cytometry. The expression changes in mRNA of proliferating cell nuclear antigen (PCNA), cyclin D1 and Bcl-xL were taken from real-time PCR analysis and the protein levels were detected by Western blotting. The results of the present study showed that Letrozole, isolated from leaves of G. pentaphylla could cause significant inhibitory effect on proliferation of IMR 32 cells in a dose dependent manner. Cell arrest was obtained at S phase with the treatment of Letrozole. Apart from this, the expression of PCNA, cyclin D1 and Bcl-xL were decreased both at mRNA and protein levels for the same treatment. Letrozole can inhibit proliferation, induce cell arrest and cause apoptosis in IMR 32 cell lines. The decreased expression of PCNA, cyclin D1 and Bcl-xL induced by Letrozole contributes to the above effects in vitro. This is the first report on the isolation of Letrozole from G. pentaphylla.

A review on anti-nutritional factors: unraveling the natural gateways to human health

Humans are constantly facing multiple health challenges from both communicable and non-communicable diseases that significantly affect their health. Additionally, drug resistance or failure has made the situation even worse and poses serious challenges for researchers to develop new drugs. Hence, to address these problems, there is an urgent need to discover and develop timely and long-term-based therapeutic treatments from different sources. One such approach is harnessing the potential of plant secondary metabolites. Plants have been utilized for therapeutic purposes in addition to being used for nutritional benefits. In the last two decades, plant-based drug developments have been one of the effective means of treating human diseases owing to their multiple functions. More recently, anti-nutritional factors (ANFs) have emerged as one of the important targets for novel plant-based drug development due to their multifaceted and potential pharmacological properties. However, their anti-nutritional properties have been the major setback for their limited success in the pharmacological sector. In this review, we provide an overview of ANFs and their beneficial roles in preventing human diseases with multiple case studies. We also highlight the recent developments and applications of ANFs in the food industry, agriculture, and pharmaceutics with future perspectives. Furthermore, we evaluate meta-analyses on ANFs from the last 30 years in relation to their function in human health benefits. This review is an endeavor to reevaluate the merit of these natural compounds and explore their potential for both human and animal health.

Multi-Targeting Neuroprotective Effects of Syzygium aromaticum Bud Extracts and Their Key Phytocompounds against Neurodegenerative Diseases

Alzheimer's disease (AD) is a neurodegenerative disease that causes a gradual loss of normal motor and cognitive function. The complex AD pathophysiology involves various factors such as oxidative stress, neuroinflammation, amyloid-beta (Aβ) aggregation, disturbed neurotransmission, and apoptosis. The available drugs suffer from a range of side effects and are not able to cover different aspects of the disease. Therefore, finding a safer therapeutic approach that can affect multiple targets at a time is highly desirable. In the present study, the underlying neuroprotective mechanism of an important culinary spice, Syzygium aromaticum (Clove) extract, and major bioactive compounds were studied in hydrogen peroxide-induced oxidative stress in human neuroblastoma SH-SY5Y cell lines as a model. The extracts were subjected to GC-MS to identify important bioactive components. The extracts and key bio-actives reduced reactive oxygen species (ROS), restored mitochondrial membrane potential (MMP), and provided neuroprotection from H2O2-induced oxidative stress in cell-based assays due to the antioxidant action. They also reduced lipid peroxidation significantly and restored GSH content. Clove extracts have also displayed anti-acetylcholinesterase (AChE) activity, anti-glycation potential, and Aβ aggregation/fibrilization inhibition. The multitarget neuroprotective approach displayed by Clove makes it a potential candidate for AD drug development.

Insight into the formation of polyhalogenated carbazoles during seawater chlorination

Although polyhalogenated carbazoles (PHCZs) have been widely detected in the marine environment, their origin is far from clear. In this study, the formation of PHCZs in the chlorination of seawater containing carbazole and its derivatives was investigated. A total of 14 PHCZs including six commonly found and eight unknown congeners were identified in the chlorination of seawater with carbazole. In addition, this study for the first time demonstrated the production of common PHCZs from the chlorination of seawater with 3-methyl carbazole and 3-formyl carbazole, especially 1,8-dibromo-3,6-dichlorocarbazole from 3-methyl carbazole. The formation of PHCZs in the reaction resulted from the halogenation of carbazole by reactive chlorine species (RCS) and mainly reactive bromine species (RBS), forming from the oxidation of bromide by RCS. Results also indicated that the reaction followed a successive halogenation pattern. A higher content of free chlorine and bromide facilitated the generation of RBS, while a higher concentration of DOC exhibited an inhibitory effect. The effects of free chlorine, bromide, DOC, and temperature on the formation of PHCZs were congener-specific. Given the widespread use of chlorination in seawater disinfection, seawater chlorination might be a potential source of PHCZs in the marine environment.

Switching Prenyl Donor Specificities in Squalene Synthase-Like Aromatic Prenyltransferases from Bacterial Carbazole Alkaloid Biosynthesis

Lavanduquinocin (LDQ) is a potent neuroprotective carbazole alkaloid from Streptomyces species that features a rare cyclic monoterpene/cyclolavandulyl moiety attached to the tricyclic carbazole nucleus. We elucidated the biosynthetic logic of LDQ by enzymatically reconstituting the total biosynthetic pathway and identified the genes required for generating the cyclolavandulyl moiety in LDQ based on mutagenetic analysis, including a cyclolavandulyl diphosphate synthase gene ldqA and a squalene synthase-like aromatic prenyltransferase gene ldqG. LdqG is homologous to carbazole prenyltransferases, NzsG and CqsB4, discovered from the biosynthetic pathways of two bacterial carbazoles, neocarazostatin and carquinostatin. Based on analysis of the sequences and modeled protein structures, further in vitro and in vivo site-directed mutagenetic analyses led to identification of two residue sites, F53 and C57 in NzsG vs I54 and A58 in LdqG, which play crucial roles in governing the prenyl donor specificities toward cyclolavandulyl, dimethylallyl, and geranyl diphosphates. By applying this knowledge in strain engineering, prenyl donor delivery was rationally switched to produce the desired prenylated carbazoles. The study provides an opportunity to rationally manipulate the prenylation modification to carbazole alkaloids, which could influence the biological activities by increasing the affinity for membranes as well as the interactions with cellular targets.

3-Methoxy Carbazole Impedes the Growth of Human Breast Cancer Cells by Suppressing NF-κB Signaling Pathway

Breast cancer represents the most frequently occurring cancer globally among women. As per the recent report of the World Health Organization (WHO), it was documented that by the end of the year 2020, approximately 7.8 million females were positively diagnosed with breast cancer and in 2020 alone, 685,000 casualties were documented due to breast cancer. The use of standard chemotherapeutics includes the frontline treatment option for patients; however, the concomitant side effects represent a major obstacle for their usage. Carbazole alkaloids are one such group of naturally-occurring bioactive compounds belonging to the Rutaceae family. Among the various carbazole alkaloids, 3-Methoxy carbazole or C13H11NO (MHC) is obtained from Clausena heptaphylla as well as from Clausena indica. In this study, MHC was investigated for its anti-breast cancer activity based on molecular interactions with specific proteins related to breast cancer, where the MHC had predicted binding affinities for NF-κB with −8.3 kcal/mol. Furthermore, to evaluate the biological activity of MHC, we studied its in vitro cytotoxic effects on MCF-7 cells. This alkaloid showed significant inhibitory effects and induced apoptosis, as evidenced by enhanced caspase activities and the cellular generation of ROS. It was observed that a treatment with MHC inhibited the gene expression of NF-kB in MCF-7 breast cancer cells. These results suggest that MHC could be a promising medical plant for breast cancer treatment. Further studies are needed to understand the molecular mechanisms behind the anticancer action of MHC.

Mechanistic Insights into the Neuroprotective Potential of Sacred Ficus Trees

Ficus religiosa (Bo tree or sacred fig) and Ficus benghalensis (Indian banyan) are of immense spiritual and therapeutic importance. Various parts of these trees have been investigated for their antioxidant, antimicrobial, anticonvulsant, antidiabetic, anti-inflammatory, analgesic, hepatoprotective, dermoprotective, and nephroprotective properties. Previous reviews of Ficus mostly discussed traditional usages, photochemistry, and pharmacological activities, though comprehensive reviews of the neuroprotective potential of these Ficus species extracts and/or their important phytocompounds are lacking. The interesting phytocompounds from these trees include many bengalenosides, carotenoids, flavonoids (leucopelargonidin-3-O-β-d-glucopyranoside, leucopelargonidin-3-O-α-l-rhamnopyranoside, lupeol, cetyl behenate, and α-amyrin acetate), flavonols (kaempferol, quercetin, myricetin), leucocyanidin, phytosterols (bergapten, bergaptol, lanosterol, β-sitosterol, stigmasterol), terpenes (α-thujene, α-pinene, β-pinene, α-terpinene, limonene, β-ocimene, β-bourbonene, β-caryophyllene, α-trans-bergamotene, α-copaene, aromadendrene, α-humulene, alloaromadendrene, germacrene, γ-cadinene, and δ-cadinene), and diverse polyphenols (tannin, wax, saponin, leucoanthocyanin), contributing significantly to their pharmacological effects, ranging from antimicrobial action to neuroprotection. This review presents extensive mechanistic insights into the neuroprotective potential, especially important phytochemicals from F. religiosa and F. benghalensis. Owing to the complex pathophysiology of neurodegenerative disorders (NDDs), the currently existing drugs merely alleviate the symptoms. Hence, bioactive compounds with potent neuroprotective effects through a multitarget approach would be of great interest in developing pharmacophores for the treatment of NDDs.

Ethnopharmacological Effects of Urtica dioica, Matricaria chamomilla, and Murraya koenigii on Rotenone-Exposed D. melanogaster: An Attenuation of Cellular, Biochemical, and Organismal Markers

Natural antioxidants derived from plants have been proven to have significant inhibitory effects on the free radicals of living organisms during actively metabolization. Excessive production of free radicals increases the risk of neurodegenerative diseases, such as Alzheimer’s disease, Parkinson’s disease, and motor sclerosis. This study aimed to compare the ethnopharmacological effects of Urtica dioica (UD), Matricaria chamomilla (MC), and Murraya koenigii (MK) on the amelioration of rotenone-induced toxicity in wild-type Drosophila melanogaster (Oregon R+) at biochemical, cellular, and behavioral levels. Phytoextracts were prepared from all three plants, i.e., UD, MC, and MK (aqueous and ethanolic fractions), and their bioactive compounds were evaluated using in vitro biochemical parameters (DPPH, ABTS, TPC, and TFC), UV-Vis, followed by FT-IR and HPLC. Third instar larvae and freshly eclosed flies were treated with 500 µM rotenone alone or in combination with UD, MC, and MK for 24 to 120 h. Following exposure, cytotoxicity (dye exclusion test), biochemical (protein estimation and acetylcholinesterase inhibition assays), and behavioral assays (climbing and jumping assays) were performed. Among all three plant extracts, MK exhibited the highest antioxidant properties due to the highest TPC, TFC, DPPH, and ABTS, followed by UD, then MC. The overall trend was MK > UD > MC. In this context, ethnopharmacological properties mimic the same effect in Drosophila, exhibiting significantly (p < 0.05) reduced cytotoxicity (trypan blue), improved biochemical parameters (proteotoxicity and AChE activity), and better behavioral parameters in the organisms cotreated with phyto extracts compared with rotenone. Conclusively, UV-Vis, FTIR, and HPLC analyses differentiated the plant extracts. The findings of this research may be beneficial in the use of select herbs as viable sources of phyto-ingredients that could be of interest in nutraceutical development and various clinical applications.

The radical scavenging activity of glycozolidol in physiological environments: a quantum chemical study

Glycozolidol (GLD), derived from Glycosmis pentaphylla, is predicted to be a good radical scavenger in physiological environments.