Activity of THC, CBD, and CBN on Human ACE2 and SARS-CoV1/2 Main Protease to Understand Antiviral Defense Mechanism

Cannabigerol and Cannabicyclol Block SARS-CoV-2 Cell Fusion

The search for new active substances against SARS-CoV-2 is still a central challenge after the COVID-19 pandemic. Antiviral agents to complement vaccination are an important pillar in the clinical situation. Selected cannabinoids such as cannabigerol, cannabicyclol, cannabichromene, and cannabicitran from Cannabis sativa and synthetic homologues of cannabigerol and cannabicyclol were evaluated for effects on the cell viability of Vero cells (CC50 of cannabigerol and cannabicyclol 40 resp. 38 µM) and reduced virus entry of vesicular stomatitis pseudotyped viruses with surface-expressed SARS-CoV-2 spike protein at 20 µM. In addition to a reduction of pseudotyped virus entry, a titer reduction assay on Vero cells after preincubation of Wuhan SARS-CoV-2 significantly confirmed antiviral activity. Investigations on the molecular targets addressed by cannabigerol and cannabicyclol indicated that both compounds are inhibitors of SARS-CoV-2 spike protein-mediated membrane fusion, as could be shown by a virus-free reporter fusion inhibition assay (EC50 for cannabigerol 5.5 µM and for cannabicyclol 10.8 µM) and by monitoring syncytia formation in Vero reporter cells. Selectivity indices were calculated as 7.4 for cannabigerol and 3.5 for cannabicyclol. Systematic semisynthetic alterations of cannabigerol and cannabicyclol indicated that the side chains of both compounds do not contribute to the observed anti-membrane fusion activity.

Comparison of decarboxylation rates of acidic cannabinoids between secretory cavity contents and air-dried inflorescence extracts in Cannabis sativa cv. 'Cherry Wine'

Studies with secretory cavity contents and air-dried inflorescence extracts of the CBD-rich hemp strain, Cannabis sativa cv. 'Cherry Wine', were conducted to compare the decarboxylation rates of acidic cannabinoids between two groups. The secretory cavity contents acquired from the capitate-stalked glandular trichomes by glass microcapillaries, and inflorescence samples air-dried for 15 days of storage in darkness at room temperature were analysed by high-pressure liquid chromatography. The ratio of acidic cannabinoids to the total cannabinoids was ranging from 0.5% to 2.4% lower in the air-dried inflorescence samples compared to the secretory cavity samples as follows. In the secretory cavity content, the percentage of acidic cannabinoids to the total cannabinoids was measured as 86.4% cannabidiolic acid (CBDA), 6.5% tetrahydrocannabinolic acid (THCA), 4.3% cannabichromenic acid (CBCA), 1.4% cannabigerolic acid (CBGA), and 0.6% cannabidivarinic acid (CBDVA), respectively. In the air-dried inflorescence, however, the acidic cannabinoids were detected with 84% CBDA, 4.8% THCA, 3.3% CBCA, 0.8% CBGA, and 0.3% Δ9-tetrahydrocannabivarinic acid (Δ9-THCVA), respectively. The ratio of cannabidiol (CBD) to cannabidiolic acid (CBDA) was close to 1:99 (w/w) in secretory cavity contents, however, it was roughly 1:20 (w/w) in the air-dried inflorescence. In addition, Δ9-tetrahydrocannabivarin (Δ9-THCV) and Δ9-tetrahydrocannabivarinic acid (Δ9-THCVA) were only detected in the air-dried inflorescence sample, and the ratio of Δ9-THCV to Δ9-THCVA was about 1:20 (w/w). Besides, cannabidivarinic acid (CBDVA) was only observed in the secretory cavity content.

Antiviral activities of hemp cannabinoids

Hemp is an understudied source of pharmacologically active compounds and many unique plant secondary metabolites including more than 100 cannabinoids. After years of legal restriction, research on hemp has recently demonstrated antiviral activities in silico, in vitro, and in vivo for cannabidiol (CBD), Δ9-tetrahydrocannabinol (Δ9-THC), cannabidiolic acid (CBDA), cannabigerolic acid (CBGA), and several other cannabinoids against severe acute respiratory syndrome coronavirus-2 (SARS-CoV-2), human immunodeficiency virus (HIV), and γ-herpes viruses. Mechanisms of action include inhibition of viral cell entry, inhibition of viral proteases, and stimulation of cellular innate immune responses. The anti-inflammatory properties of cannabinoids are also under investigation for mitigating the cytokine storm of COVID-19 and controlling chronic inflammation in people living with HIV. Retrospective clinical studies support antiviral activities of CBD, Δ9-THC, and cannabinoid mixtures as do some prospective clinical trials, but appropriately designed clinical trials of safety and efficacy of antiviral cannabinoids are urgently needed.

Chemical Constituents from Streblus taxoides Wood with Their Antibacterial and Antityrosinase Activities Plus in Silico Study

Hyperpigmentation frequently occurs after inflammation from bacterial infection. Thus, the inhibition activity of tyrosinase, the key enzyme to catalyze the melanogenesis and/or inhibition of bacterial infection, could decrease melanin production. Hence, the potential inhibitors could be discovered from natural products. ω-Hydroxymoracin C (1), a new compound with two other 2-arylbenzofurans, i.e., moracin M (2) and moracin C (3), and two stilbenes, i.e., 3, 4, 3', 5'-tetrahydroxybibenzyl (4) and piceatannol (5), were isolated from the wood of Streblus taxoides. Compound 4 showed a strong inhibitory activity against tyrosinase enzyme with an IC₅₀ value of 35.65 µg/mL, followed by compound 2 with an IC₅₀ value of 47.34 µg/mL. Conversely, compound 1, 3 and 5 showed moderate activity, with IC₅₀ values of 109.64, 128.67 and 149.73 µg/mL, respectively. Moreover, compound 1 and 3 showed an antibacterial effect against some Staphylococcus spp. Thus, the isolated compounds exhibited potential antityrosine and antibacterial effects. Additionally, an in silico study was performed in order to predict theoretical molecular interactions between the obtained metabolites from S. taxoides and tyrosinase as an extended in vitro enzyme binding assay experiment.

Small molecules in the treatment of COVID-19

The outbreak of COVID-19 has become a global crisis, and brought severe disruptions to societies and economies. Until now, effective therapeutics against COVID-19 are in high demand. Along with our improved understanding of the structure, function, and pathogenic process of SARS-CoV-2, many small molecules with potential anti-COVID-19 effects have been developed. So far, several antiviral strategies were explored. Besides directly inhibition of viral proteins such as RdRp and M^pro, interference of host enzymes including ACE2 and proteases, and blocking relevant immunoregulatory pathways represented by JAK/STAT, BTK, NF-κB, and NLRP3 pathways, are regarded feasible in drug development. The development of small molecules to treat COVID-19 has been achieved by several strategies, including computer-aided lead compound design and screening, natural product discovery, drug repurposing, and combination therapy. Several small molecules representative by remdesivir and paxlovid have been proved or authorized emergency use in many countries. And many candidates have entered clinical-trial stage. Nevertheless, due to the epidemiological features and variability issues of SARS-CoV-2, it is necessary to continue exploring novel strategies against COVID-19. This review discusses the current findings in the development of small molecules for COVID-19 treatment. Moreover, their detailed mechanism of action, chemical structures, and preclinical and clinical efficacies are discussed.

Cross-Talk between the (Endo)Cannabinoid and Renin-Angiotensin Systems: Basic Evidence and Potential Therapeutic Significance

This review is dedicated to the cross-talk between the (endo)cannabinoid and renin angiotensin systems (RAS). Activation of AT₁ receptors (AT₁Rs) by angiotensin II (Ang II) can release endocannabinoids that, by acting at cannabinoid CB₁ receptors (CB₁Rs), modify the response to AT₁R stimulation. CB₁R blockade may enhance AT₁R-mediated responses (mainly vasoconstrictor effects) or reduce them (mainly central nervous system-mediated effects). The final effects depend on whether stimulation of CB₁Rs and AT₁Rs induces opposite or the same effects. Second, CB₁R blockade may diminish AT₁R levels. Third, phytocannabinoids modulate angiotensin-converting enzyme-2. Additional studies are required to clarify (1) the existence of a cross-talk between the protective axis of the RAS (Ang II—AT₂ receptor system or angiotensin 1-7—Mas receptor system) with components of the endocannabinoid system, (2) the influence of Ang II on constituents of the endocannabinoid system and (3) the (patho)physiological significance of AT₁R-CB₁R heteromerization. As a therapeutic consequence, CB₁R antagonists may influence effects elicited by the activation or blockade of the RAS; phytocannabinoids may be useful as adjuvant therapy against COVID-19; single drugs acting on the (endo)cannabinoid system (cannabidiol) and the RAS (telmisartan) may show pharmacokinetic interactions since they are substrates of the same metabolizing enzyme of the transport mechanism.