Stephen J. Cutler

Neuropeptide FF (NPFF) receptor antagonists prevent morphine-mediated antinociceptive tolerance, and compounds with dual mu opioid receptor (MOR) agonist and NPFF antagonist activity produce antinociception without tolerance. Compounds synthesized showed affinities in radioligand competition binding assays in the nM and µM range at the opioid and NPFF receptors, respectively, and displayed substitution-dependent functional profiles in the [³⁵S]GTPγS functional assay. From six compounds screened in vivo for antinociception and ability to prevent NPFF-induced hyperalgesia in mouse warm water tail withdrawal tests, compound 22b produced dose-dependent MOR-mediated antinociception with an ED₅₀ value (and 95% confidence interval) of 6.88 (4.71–9.47) nmol, i.c.v., and also prevented NPFF-induced hyperalgesia. Meanwhile, 22b did not demonstrate the respiratory depression, hyperlocomotion, or impaired intestinal transit of morphine. Moreover, repeated treatment with 22b produced a 1.6-fold rightward shift in antinociceptive dose response, significantly less acute antinociceptive tolerance than morphine. Evaluated for microsomal stability in vitro and in vivo pharmacokinetic profile, 22b showed suitable microsomal stability paired in vivo with a large apparent volume of distribution and a clearance smaller than the hepatic flow in rats, suggesting no extra-hepatic metabolism. In conclusion, the present study confirms that dual-action opioid–NPFF ligands may offer therapeutic promise as analgesics with fewer liabilities of use.

Cannabidiol (CBD) is a major phytocannabinoid present in Cannabis sativa (Linneo, 1753). This naturally occurring secondary metabolite does not induce intoxication or exhibit the characteristic profile of drugs of abuse from cannabis like Δ⁹-tetrahydrocannabinol (∆⁹-THC) does. In contrast to ∆⁹-THC, our knowledge of the neuro-molecular mechanisms of CBD is limited, and its pharmacology, which appears to be complex, has not yet been fully elucidated. The study of the pharmacological effects of CBD has grown exponentially in recent years, making it necessary to generate frequently updated reports on this important metabolite. In this article, a rationalized integration of the mechanisms of action of CBD on molecular targets and pharmacological implications in animal models and human diseases, such as epilepsy, pain, neuropsychiatric disorders, Alzheimer’s disease, and inflammatory diseases, are presented. We identify around 56 different molecular targets for CBD, including enzymes and ion channels/metabotropic receptors involved in neurologic conditions. Herein, we compiled the knowledge found in the scientific literature on the multiple mechanisms of actions of CBD. The in vitro and in vivo findings are essential for fully understanding the polypharmacological nature of this natural product.

A series of dietary flavonoid acacetin 7-O-methyl ether derivatives were computationally designed aiming to improve the selectivity and potency profiles against monoamine oxidase (MAO) B. The designed compounds were evaluated for their potential to inhibit human MAO-A and -B. Compounds 1c, 2c, 3c, and 4c were the most potent with a Ki of 37 to 68 nM against MAO-B. Compounds 1c–4c displayed more than a thousand-fold selectivity index towards MAO-B compared with MAO-A. Moreover, compounds 1c and 2c showed reversible inhibition of MAO-B. These results provide a basis for further studies on the potential application of these modified flavonoids for the treatment of Parkinson’s Disease and other neurological disorders.

The goal of this study was to assess the pharmacological effects of black tea (Camellia sinensis var. assamica) water extract on human kinin-forming enzymes in vitro. Tea is a highly consumed beverage in the world. Factor XII (FXII, Hageman factor)-independent- and -dependent activation of prekallikrein to kallikrein leads to the liberation of bradykinin (BK) from high-molecular-weight kininogen (HK). The excessive BK production causes vascular endothelial and nonvascular smooth muscle cell permeability, leading to angioedema. The prevalence of angiotensin-converting enzyme inhibitor (ACEI)-induced angioedema appears to be through BK. Both histamine and BK are potent inflammatory mediators. However, the treatments for histamine-mediated angioedema are unsuitable for BK-mediated angioedema. We hypothesized that long-term consumption of tea would reduce bradykinin-dependent processes within the systemic and pulmonary vasculature, independent of the anti-inflammatory actions of polyphenols. A purified fraction of the black tea water extract inhibited both kallikrein and activated FXII. The black tea water extracts inhibited factor XII-induced cell migration and inhibited the production of kallikrein on the endothelial cell line. We compared the inhibitory effects of the black tea water extract and twenty-three well-known anti-inflammatory medicinal herbs, in inhibiting both kallikrein and FXII. Surprisingly, arjunglucoside II specifically inhibited the activated factor XII (FXIIa), but not the kallikrein and the activated factor XI. Taken together, the black tea water extract exerts its anti-inflammatory effects, in part, by inhibiting kallikrein and activated FXII, which are part of the plasma kallikrein–kinin system (KKS), and by decreasing BK production. The inhibition of kallikrein and activated FXII represents a unique polyphenol-independent anti-inflammatory mechanism of action for the black tea.

Ovarian cancer is a fatal gynecological cancer because of a lack of early diagnosis, which often relapses as chemoresistant. Trichodermin, a trichothecene first isolated from Trichoderma viride, is an inhibitor of eukaryotic protein synthesis. However, whether trichodermin is able to suppress ovarian cancer or not was unclear. In this study, trichodermin (0.5 µM or greater) significantly decreased the proliferation of two ovarian cancer cell lines A2780/CP70 and OVCAR-3. Normal ovarian IOSE 346 cells were much less susceptible to trichodermin than the cancer cell lines. Trichodermin predominantly inhibited ovarian cancer cells by inducing G0/G1 cell cycle arrest rather than apoptosis. Trichodermin decreased the expression of cyclin D1, CDK4, CDK2, retinoblastoma protein, Cdc25A, and c-Myc but showed little effect on the expression of p21^Waf1/Cip1, p27^Kip1, or p16^Ink4a. c-Myc was a key target of trichodermin. Trichodermin regulated the expression of Cdc25A and its downstream proteins via c-Myc. Overexpression of c-Myc attenuated trichodermin’s anti-ovarian cancer activity. In addition, trichodermin decelerated tumor growth in BALB/c nude mice, proving its effectiveness in vivo. These findings suggested that trichodermin has the potential to contribute to the treatment of ovarian cancer.

The in vitro activity of L. donovani (promastigotes, axenic amastigotes and intracellular amastigotes in THP1 cells) and T. brucei, from the fractions obtained from the hydroalcoholic extract of the aerial part of Hypericum afrum and the isolated compounds, has been evaluated. The chloroform, ethyl acetate and n-butanol extracts showed significant antitrypanosomal activity towards T. brucei, with IC₅₀ values of 12.35, 13.53 and 12.93 µg/mL and with IC₉₀ values of 14.94, 19.31 and 18.67 µg/mL, respectively. The phytochemical investigation of the fractions led to the isolation and identification of quercetin (1), myricitrin (2), biapigenin (3), myricetin (4), hyperoside (5), myricetin-3-O-β-d-galactopyranoside (6) and myricetin-3’-O-β-d-glucopyranoside (7). Myricetin-3’-O-β-d-glucopyranoside (7) has been isolated for the first time from this genus. The chemical structures were elucidated by using comprehensive one- and two-dimensional nuclear magnetic resonance (1D and 2D NMR) spectroscopic data, as well as high-resolution electrospray ionization mass spectrometry (HR-ESI–MS). These compounds have also been evaluated for their antiprotozoal activity. Quercetin (1) and myricetin (4) showed noteworthy activity against T. brucei, with IC₅₀ and IC₉₀ values of 7.52 and 5.71 µM, and 9.76 and 7.97 µM, respectively. The T. brucei hexokinase (TbHK1) enzyme was further explored as a potential target of quercetin and myricetin, using molecular modeling studies. This proposed mechanism assists in the exploration of new candidates for novel antitrypanosomal drugs.

The aim of this study was to evaluate the total phenolic and flavonoid content, and the in vitro antioxidant, anti-inflammatory, antibacterial, antifungal, antimalarial, cytotoxicity, and antiprotozoal activities of the Algerian plant Cytisus villosus Pourr. (Syn. Cytisus triflorus L’Hérit.). Additionally, the radioligand displacement affinity on opioid and cannabinoid receptors was assessed for the extracts and isolated pure compounds. The hydro alcoholic extract of the aerial part of C. villosus was partitioned with chloroform (CHCl₃), ethyl acetate (EtOAc), and n-butanol (n-BuOH). The phenolic content of the C. villosus extracts was evaluated using a modified Folin–Ciocalteau method. The total flavonoid content was measured spectrometrically using the aluminum chloride colorimetric assay. The known flavonoids genistein (1), chrysin (2), chrysin-7-O-β-d-glucopyranoside (3), and 2″-O-α-l-rhamnosylorientin (4) were isolated. The antioxidant activities of the extracts and isolated compounds were evaluated using 2,2-diphenyl-1-picrylhydrazyl (DDPH) and cellular antioxidant activity (CAA) assays. The plant extracts showed moderate antioxidant activity. EtOAc and n-BuOH extracts showed moderate anti-inflammatory activity through the inhibition of induced nitric oxide synthase (iNOS) with IC₅₀ values of 48 and 90 µg/mL, respectively. The isolated pure compounds 1 and 3 showed good inhibition of Inducible nitric oxide synthase (iNOS) with IC₅₀ values of 9 and 20 µg/mL, respectively. Compounds 1 and 2 exhibited lower inhibition of Nuclear Factor kappa-light-chain-enhancer of activated B cells (NF-κB) with IC₅₀ values of 28 and 38 µg/mL, respectively. Furthermore, the extracts and isolated pure compounds have been shown to exhibit low affinity for cannabinoid and opioid receptors. Finally, n-BuOH extract was a potent inhibitor of Trypanosoma brucei with IC₅₀ value of 7.99 µg/mL and IC₉₀ value of 12.61 µg/mL. The extracts and isolated compounds showed no antimicrobial, antimalarial nor antileishmanial activities. No cytotoxic effect was observed on cancer cell lines. The results highlight this species as a promising source of anti-inflammatory and antitrypanosomal agents.

Natural products are an abundant source of potential drugs, and their diversity makes them a rich and viable prospective source of bioactive cannabinoid ligands. Cannabinoid receptor 1 (CB1) antagonists are clinically established and well documented as potential therapeutics for treating obesity, obesity-related cardiometabolic disorders, pain, and drug/substance abuse, but their associated CNS-mediated adverse effects hinder the development of potential new drugs and no such drug is currently on the market. This limitation amplifies the need for new agents with reduced or no CNS-mediated side effects. We are interested in the discovery of new natural product chemotypes as CB1 antagonists, which may serve as good starting points for further optimization towards the development of CB1 therapeutics. In search of new chemotypes as CB1 antagonists, we screened the in silico purchasable natural products subset of the ZINC12 database against our reported CB1 receptor model using the structure-based virtual screening (SBVS) approach. A total of 18 out of 192 top-scoring virtual hits, selected based on structural diversity and key protein–ligand interactions, were purchased and subjected to in vitro screening in competitive radioligand binding assays. The in vitro screening yielded seven compounds exhibiting >50% displacement at 10 μM concentration, and further binding affinity (K_i and IC₅₀) and functional data revealed compound 16 as a potent and selective CB1 inverse agonist (K_i = 121 nM and EC₅₀ = 128 nM) while three other compounds—2, 12, and 18—were potent but nonselective CB1 ligands with low micromolar binding affinity (K_i). In order to explore the structure–activity relationship for compound 16, we further purchased compounds with >80% similarity to compound 16, screened them for CB1 and CB2 activities, and found two potent compounds with sub-micromolar activities. Most importantly, these bioactive compounds represent structurally new natural product chemotypes in the area of cannabinoid research and could be considered for further structural optimization as CB1 ligands.

A series of isoxazole and triazole derivatives, with interesting bioactive scaffolds, were examined for their in vitro antibacterial, antifungal, and antiprotozoal activities. These compounds exhibited antitrypanosomal activity comparable to difluoromethylornithine (DMFO), a drug used in the treatment of human African trypanosomiasis. Isoxazole analogs 1, 3, and 4, and triazole derivatives 16, 17, 28, 37, 40, and 42 showed the highest antitrypanosomal activity with IC₅₀ values of 17.89, 1.82, 10.38, 10.26, 11.77, 9.29, 3.93, 2.11, and 0.93 µM, respectively. Compounds 40 and 42 showed the most potent activity against Leishmania donovani amastigotes with IC₅₀ values of 18.28 and 10.54 µM, respectively. Compound 42 showed the most potent activity against Leishmania donovani macrophage internalized amastigotes with an IC₅₀ value of 8.32 µM. Conjugate triazoles 40–43 displayed potential antimalarial activity against chloroquine-resistant W2 and chloroquine-sensitive D6 Plasmodium falciparum strains (IC₅₀ value range from 0.58 to 8.36 µM). Compound 37 showed antibacterial activity against Staphylococcus aureus, MRSA, and Mycobacterium intracellulare with IC₅₀ values of 15.53, 14.22, and 47.45 µM, respectively. None of the compounds exhibited antifungal activity.