Iodine-Promoted Aromatization of p-Menthane-Type Phytocannabinoids

Cannabinol Regulates the Expression of Cell Cycle-Associated Genes in Motor Neuron-like NSC-34: A Transcriptomic Analysis

Cannabinoids are reported to have neuroprotective properties and play a role in neurogenesis and neuroplasticity in in vitro and in vivo models. Cannabinol (CBN) is a minor cannabinoid produced by the degradation of Δ9-tetrahydrocannabinol in Cannabis sativa L. and exhibits anti-oxidant, analgesic, anti-bacterial, and anti-inflammatory effects. In this study, we explored the biological effects of 20 µM CBN (6.20 µg/mL) on differentiated NSC-34 cells by MTT assay and next-generation sequencing analysis on the transcriptome. KEGG and Gene Ontology enrichment analyses have been performed to evaluate potential CBN-associated processes. Our results highlighted the absence of any cytotoxic effect of CBN. The comparative transcriptomic analysis pointed out the downregulation of Cdkn2a, Cdkn2c and Cdkn2d genes, which are known to suppress the cell cycle. Ccne2, Cdk2, Cdk7, Anapc11, Anapc10, Cdc23, Cdc16, Anapc4, Cdc27, Stag1, Smc3, Smc1a, Nipbl, Pds5a, Pds5b, and Wapl genes, renowned for their role as cell cycle progression activators, were instead upregulated. Our work suggests that CBN regulates the expression of many genes related to the cell cycle, which are required for axonal maturation, migration, and synaptic plasticity, while not affecting the expression of genes involved in cell death or tumorigenesis.

Easy and Accessible Synthesis of Cannabinoids from CBD

Cannabidiol (CBD), a prominent phytocannabinoid found in various Cannabis chemotypes, is under extensive investigation for its therapeutic potential. Moreover, because it is nonpsychoactive, it can also be utilized as a functional ingredient in foods and supplements in certain countries, depending on its legal status. From a chemical reactivity point of view, CBD can undergo conversion into different structurally related compounds both during storage and after the consumption of CBD-based products. The analytical determination of these compounds is of paramount concern due to potential toxicity and the risk of losing the active ingredient (CBD) title. Consequently, the complete stereoselective total synthesis of representative CBD-derived compounds has become a matter of great interest. The synthesis of pure CBD-derived compounds, achievable in a few synthetic steps, is essential for preparing analytical standards and facilitating biological studies. This paper details the transformation of the readily available CBD into Δ8-THC, Δ9-THC, Δ8-iso-THC, CBE, HCDN, CBDQ, Δ6-iso-CBD, and 1,8-cineol cannabinoid (CCB). The described protocols were executed without the extensive use of protecting groups, avoiding tedious purifications, and ensuring complete control over the structural features.

Transcriptome Highlights Cannabinol Modulation of Mitophagy in a Parkinson's Disease In Vitro Model

Parkinson's disease (PD) is a neurodegenerative disorder characterized by the loss of dopaminergic neurons in the substantia nigra and the accumulation of α-synuclein aggregates, known as Lewy bodies. It is known that mitochondria dysfunctions, including impaired localization, transport and mitophagy, represent features of PD. Cannabinoids are arising as new therapeutic strategies against neurodegenerative diseases. In this study, we aimed to evaluate the potential protective effects of cannabinol (CBN) pre-treatment in an in vitro PD model, namely retinoic acid-differentiated SH-SY5Y neuroblastoma cells treated with 1-methyl-4-phenylpyridinium (MPP+). With this aim, we performed a transcriptomic analysis through next-generation sequencing. We found that CBN counteracted the loss of cell viability caused by MPP+ treatment. Then, we focused on biological processes relative to mitochondria functions and found that CBN pre-treatment was able to attenuate the MPP+-induced changes in the expression of genes involved in mitochondria transport, localization and protein targeting. Notably, MPP+ treatment increased the expression of the genes involved in PINK1/Parkin mitophagy, while CBN pre-treatment reduced their expression. The results suggested that CBN can exert a protection against MPP+ induced mitochondria impairment.

Cannabinol: History, Syntheses, and Biological Profile of the Greatest "Minor" Cannabinoid

Cannabis (Cannabis sativa L.) is an outstanding source of bioactive natural products, with more than 150 different phytocannabinoids isolated throughout the decades; however, studies of their bioactivity have historically concentrated on the so-called "big four" [∆⁹-THC (1a), CBD (2a), CBG (3a) and CBC (4a)]. Among the remaining products, which have traditionally been referred to as "minor cannabinoids", cannabinol (CBN, 5a) stands out for its important repercussions and implications on the global scientific landscape. Throughout this review, we will describe why CBN (5a) deserves a prominent place within the so-called "cannabinome", providing an overview on its history, the syntheses developed, and its bioactivity, highlighting its promising pharmacological potential and the significant impact that the study of its chemistry had on the development of new synthetic methodologies.

Minor Phytocannabinoids: A Misleading Name but a Promising Opportunity for Biomedical Research

Despite the very large number of phytocannabinoids isolated from Cannabis (Cannabis sativa L.), bioactivity studies have long remained focused on the so called “Big Four” [Δ⁹-THC (1), CBD (2), CBG (3) and CBC (4)] because of their earlier characterization and relatively easy availability via isolation and/or synthesis. Bioactivity information on the chemical space associated with the remaining part of the cannabinome, a set of ca 150 compounds traditionally referred to as “minor phytocannabinoids”, is scarce and patchy, yet promising in terms of pharmacological potential. According to their advancement stage, we sorted the bioactivity data available on these compounds, better referred to as the “dark cannabinome”, into categories: discovery (in vitro phenotypical and biochemical assays), preclinical (animal models), and clinical. Strategies to overcome the availability issues associated with minor phytocannabinoids are discussed, as well as the still unmet challenges facing their development as mainstream drugs.

Synthetic Strategies for Rare Cannabinoids Derived from Cannabis sativa

Efficient syntheses of eight key cannabinoids were established and optimized. Predominant cannabinoids such as cannabigerol (CBG-C₅) and cannabidiol (CBD-C₅) were prepared from olivetol via regioselective condensation. Further treatments of CBD led to Δ⁹-tetrahydrocannabinol (THC-C₅), Δ⁸-iso-tetrahydrocannabinol (iso-THC-C₅), and cannabinol (CBN-C₅). Alternatively, a [3 + 3] annulation between olivetol and citral yielded the minor cannabinoid cannabichromene (CBC-C₅), which was converted into two very rare polycycles, cannabicyclol (CBL-C₅) and cannabicitran (CBT-C₅), in a one-pot reaction. Finally, all eight syntheses were extended by utilizing resorcinol and two phenolic analogues, achieving a cannabinoid group with more than 30 compounds through a facile synthesis strategy.

The Combined Effect of Branching and Elongation on the Bioactivity Profile of Phytocannabinoids. Part I: Thermo-TRPs

The affinity of cannabinoids for their CB₁ and CB₂ metabotropic receptors is dramatically affected by a combination of α-branching and elongation of their alkyl substituent, a maneuver exemplified by the n-pentyl -> α,α-dimethylheptyl (DMH) swap. The effect of this change on other cannabinoid end-points is still unknown, an observation surprising since thermo-TRPs are targeted by phytocannabinoids with often sub-micromolar affinity. To fill this gap, the α,α-dimethylheptyl analogues of the five major phytocannabinoids [CBD (1a), Δ⁸-THC (6a), CBG (7a), CBC (8a) and CBN (9a)] were prepared by total synthesis, and their activity on thermo-TRPs (TRPV1-4, TRPM8, and TRPA1) was compared with that of one of their natural analogues. Surprisingly, the DMH chain promoted a shift in the selectivity toward TRPA1, a target involved in pain and inflammatory diseases, in all investigated compounds. A comparative study of the putative binding modes at TRPA1 between DMH-CBC (8b), the most active compound within the series, and CBC (8a) was carried out by molecular docking, allowing the rationalization of their activity in terms of structure–activity relationships. Taken together, these observations qualify DMH-CBC (8b) as a non-covalent TRPA1-selective cannabinoid lead that is worthy of additional investigation as an analgesic and anti-inflammatory agent.

Novel cannabidiol-carbamate hybrids as selective BuChE inhibitors: Docking-based fragment reassembly for the development of potential therapeutic agents against Alzheimer's disease

Cannabidiol (CBD) and rivastigmine have been launched as drugs for treating dementia and cholinesterases (ChEs) are ideal drug targets. This study focused on developing novel ChE inhibitors as drug leads against dementia through molecular modeling and fragment reassembly approaches. A potent carbamate fragment binding to active site gorge of BuChE was found via a docking-based structural splicing approach, thus, 17 novel compounds were designed by structural reassembly. Compound C16 was identified as a highly selective potent BuChE inhibitor (IC₅₀ = 5.3 nM, SI > 4000), superior to CBD (IC₅₀ = 0.67 μM). C16 possessed BBB penetrating ability, benign safety, neuroprotection, antioxidant and pseudo-irreversible BuChE inhibition (K_d = 13 nM, k₂ = 0.26 min^-1), showing good drug-like properties. In vivo studies confirmed that C16 significantly ameliorated the scopolamine-induced cognition impairment, almost entirely recovered the Aβ_1-42 (icv)-impaired cognitive function to the normal level, showed better behavioral performance than donepezil and good anti-amyloidogenic effect. Hence, the potential BuChE inhibitor C16 can be developed as a promising disease-modifying treatment of AD.

Antioxidant function of phytocannabinoids: Molecular basis of their stability and cytoprotective properties under UV-irradiation

In this contribution, a comprehensive study of the redox transformation, electronic structure, stability and photoprotective properties of phytocannabinoids is presented. The non-psychotropic cannabidiol (CBD), cannabigerol (CBG), cannabinol (CBN), cannabichromene (CBC), and psychotropic tetrahydrocannabinol (THC) isomers and iso-THC were included in the study. The results show that under aqueous ambient conditions at pH 7.4, non-psychotropic cannabinoids are slight or moderate electron-donors and they are relatively stable, in the following order: CBD > CBG ≥ CBN > CBC. In contrast, psychotropic Δ⁹-THC degrades approximately one order of magnitude faster than CBD. The degradation (oxidation) is associated with the transformation of OH groups and changes in the double-bond system of the investigated molecules. The satisfactory stability of cannabinoids is associated with the fact that their OH groups are fully protonated at pH 7.4 (pKa is ≥ 9). The instability of CBN and CBC was accelerated after exposure to UVA radiation, with CBD (or CBG) being stable for up to 24 h. To support their topical applications, an in vitro dermatological comparative study of cytotoxic, phototoxic and UVA or UVB photoprotective effects using normal human dermal fibroblasts (NHDF) and keratinocytes (HaCaT) was done. NHDF are approx. twice as sensitive to the cannabinoids' toxicity as HaCaT. Specifically, toxicity IC₅₀ values for CBD after 24 h of incubation are 7.1 and 12.8 μM for NHDF and HaCaT, respectively. None of the studied cannabinoids were phototoxic. Extensive testing has shown that CBD is the most effective protectant against UVA radiation of the studied cannabinoids. For UVB radiation, CBN was the most effective. The results acquired could be used for further redox biology studies on phytocannabinoids and evaluations of their mechanism of action at the molecular level. Furthermore, the UVA and UVB photoprotectivity of phytocannabinoids could also be utilized in the development of new cannabinoid-based topical preparations.

Phytocannabinoid Pharmacology: Medicinal Properties of Cannabis sativa Constituents Aside from the "Big Two"

Plant-based therapies date back centuries. Cannabis sativa is one such plant that was used medicinally up until the early part of the 20th century. Although rich in diverse and interesting phytochemicals, cannabis was largely ignored by the modern scientific community due to its designation as a schedule 1 narcotic and restrictions on access for research purposes. There was renewed interest in the early 1990s when the endocannabinoid system (ECS) was discovered, a complex network of signaling pathways responsible for physiological homeostasis. Two key components of the ECS, cannabinoid receptor 1 (CB1) and cannabinoid receptor 2 (CB2), were identified as the molecular targets of the phytocannabinoid Δ⁹-tetrahydrocannabinol (Δ⁹-THC). Restrictions on access to cannabis have eased worldwide, leading to a resurgence in interest in the therapeutic potential of cannabis. Much of the focus has been on the two major constituents, Δ⁹-THC and cannabidiol (CBD). Cannabis contains over 140 phytocannabinoids, although only a handful have been tested for pharmacological activity. Many of these minor cannabinoids potently modulate receptors, ionotropic channels, and enzymes associated with the ECS and show therapeutic potential individually or synergistically with other phytocannabinoids. The following review will focus on the pharmacological developments of the next generation of phytocannabinoid therapeutics.

Cannabitwinol, a Dimeric Phytocannabinoid from Hemp, Cannabis sativa L., Is a Selective Thermo-TRP Modulator

Cannabitwinol (CBDD, 3), the second member of a new class of dimeric phytocannabinoids in which two units are connected by a methylene bridge, was isolated from a hemp (Cannabis sativa L.) industrial extract. The structural characterization of cannabitwinol, complicated by broadening of ¹H NMR signals and lack of expected 2D NMR correlations at room temperature, was fully carried out in methanol-d₄ at -30 °C. All the attempts to prepare CBDD by reaction of CBD with formaldehyde or its iminium analogue (Eschenmoser salt) failed, suggesting that this sterically congested dimer is the result of enzymatic reactions on the corresponding monomeric acids. Analysis of the cannabitwinol profile of transient receptor potential (TRP) modulation evidenced the impact of dimerization, revealing a selectivity for channels activated by a decrease of temperature (TRPM8 and TRPA1) and the lack of significant affinity for those activated by an increase of temperature (e.g., TRPV1). The putative binding modes of cannabitwinol with TRPA1 and TRPM8 were investigated in detail by a molecular docking study using the homology models of both channels.

Mammalian Transient Receptor Potential TRPA1 Channels: From Structure to Disease

The transient receptor potential ankyrin (TRPA) channels are Ca²⁺-permeable nonselective cation channels remarkably conserved through the animal kingdom. Mammals have only one member, TRPA1, which is widely expressed in sensory neurons and in non-neuronal cells (such as epithelial cells and hair cells). TRPA1 owes its name to the presence of 14 ankyrin repeats located in the NH₂ terminus of the channel, an unusual structural feature that may be relevant to its interactions with intracellular components. TRPA1 is primarily involved in the detection of an extremely wide variety of exogenous stimuli that may produce cellular damage. This includes a plethora of electrophilic compounds that interact with nucleophilic amino acid residues in the channel and many other chemically unrelated compounds whose only common feature seems to be their ability to partition in the plasma membrane. TRPA1 has been reported to be activated by cold, heat, and mechanical stimuli, and its function is modulated by multiple factors, including Ca²⁺, trace metals, pH, and reactive oxygen, nitrogen, and carbonyl species. TRPA1 is involved in acute and chronic pain as well as inflammation, plays key roles in the pathophysiology of nearly all organ systems, and is an attractive target for the treatment of related diseases. Here we review the current knowledge about the mammalian TRPA1 channel, linking its unique structure, widely tuned sensory properties, and complex regulation to its roles in multiple pathophysiological conditions.

One-Pot Total Synthesis of Cannabinol via Iodine-Mediated Deconstructive Annulation

The thermal degradation of cannabichromene (CBC, 3) is dominated by cationic reactions and not by the pericyclic rearrangements observed in model compounds. The rationalization of these differences inspired the development of a process that coupled, in an aromatization-driven single operational step, the condensation of citral and alkylresorciniols to homoprenylchromenes and their in situ deconstructive annulation to benzo[c]chromenes. This process was applied to a total synthesis of cannabinol (CBN, 5) and to its molecular editing.

Biomimetic Transformation of p-Menthene Glucosides into p-Cymenes and Carvotanacetone

A biomimetic transformation of p-menthene glucosides into aromatic monoterpenoids that alluded to mechanisms for essential oil metabolism, which lines up with the precepts of molecular economy, is described. Acid treatment of (-)-(3 S,4 S,6 R)-3,6-dihydroxy-1-menthene 3- O-β-d-glucopyranoside (1) and (-)-(3 S,4 R,5 R,6 S)-3,5,6-trihydroxy-1-menthene 3- O-β-d-glucopyranoside (2), from Ageratina glabrata, yielded p-cymene (7) and carvacrol (9). The stable oxidized intermediates (+)-(3 S,4 S,6 R)-3,6-dihydroxy-1-menthene (3), (+)-(1 S,4 S,6 R)-1,6-dihydroxy-2-menthene (4), (+)-(1 R,4 S,6 R)-1,6-dihydroxy-2-menthene (5), (+)-(4 S,6 R)-yabunikkeol (6), (+)-(4 S)-carvotanacetone (8), (+)-(1 S,4 S,5 R,6 R)-1,5,6-trihydroxy-2-menthene (15), (+)-(1 R,4 S,5 R,6 R)-1,5,6-trihydroxy-2-menthene (16), and the new (+)-(4 S,5 R,6 S)-1(7),2-menthadiene (17) permitted establishment of the reaction mechanisms. The reactivity of the hydroxy groups of 4 and 5, as well as those of 15 and 16, was compared by acetylation reactions and supported by DFT calculations, revealing diminished reactivity in 4 and 15 due to the cis configuration of their hydroxy groups at C-1 and C-6. In addition, p-cymene (7) was detected as one of the major constituents of the essential oil of A. glabrata, which matches well with the biomimetic study.