Insight into the Mechanisms Underlying the Tracheorelaxant Properties of the Sideritis raeseri Extract

Flavonoids derived from medicinal plants as a COVID-19 treatment

The severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) causes COVID-19 disease. Through its viral spike (S) protein, the virus enters and infects epithelial cells by utilizing angiotensin-converting enzyme 2 as a host cell's receptor protein. The COVID-19 pandemic had a profound impact on global public health and economies. Although various effective vaccinations and medications are now available to prevent and treat COVID-19, natural compounds derived from medicinal plants, particularly flavonoids, demonstrated therapeutic potential to treat COVID-19 disease. Flavonoids exhibit dual antiviral mechanisms: direct interference with viral invasion and inhibition of replication. Specifically, they target key viral molecules, particularly viral proteases, involved in infection. These compounds showcase significant immunomodulatory and anti-inflammatory properties, effectively inhibiting various inflammatory cytokines. Additionally, emerging evidence supports the potential of flavonoids to mitigate the progression of COVID-19 in individuals with obesity by positively influencing lipid metabolism. This review aims to elucidate the molecular structure of SARS-CoV-2 and the underlying mechanism of action of flavonoids on the virus. This study evaluates the potential anti-SARS-CoV-2 properties exhibited by flavonoid compounds, with a specific interest in their structure and mechanisms of action, as therapeutic applications for the prevention and treatment of COVID-19. Nevertheless, a significant portion of existing knowledge is based on theoretical frameworks and findings derived from in vitro investigations. Further research is required to better assess the effectiveness of flavonoids in combating SARS-CoV-2, with a particular emphasis on in vivo and clinical investigations.

Comparative Study on Assisted Solvent Extraction Techniques for the Extraction of Biologically Active Compounds from Sideritis raeseri and Sideritis scardica

The plants in the Sideritis genus are postulated to exhibit several important medicinal properties due to their unique chemical composition. To isolate the targeted phytochemical compounds, the selection of a suitable extraction method is of primary importance. In this work, a comparative study on the phytochemical profiles of various Sideritis raeseri and Sideritis scardica extracts has been carried out. An untargeted metabolomics approach based on ultra-high performance liquid chromatography coupled with high-resolution mass spectrometry was applied to investigate the metabolic differences between extracts obtained by conventional extraction and extractions assisted by microwaves, ultrasounds and high pressure. Additionally, the influence of extraction solvents on HPLC antioxidant profiles obtained following the derivatization of analytes with ABTS reagent was evaluated. A total of 102 metabolites have been putatively identified. The major secondary metabolites groups were classified as flavonoids, terpenoids, phenylethanoid glycosides and phenolic acids. The main antioxidants in the extracts were isoscutellarein and hypolaetin derivatives as well as verbascoside and chlorogenic acid. The results showed that 70% ethanol was the most effective extractant for different classes of phytochemicals including antioxidants. In addition, extraction supported with microwaves, ultrasounds or high pressure improved the overall recovery of metabolites by about 3 times compared to the conventional extraction method.

Vasorelaxant Effects of the Vitex Agnus-Castus Extract

This study was undertaken to describe and characterize the relaxing effects of the medicinal plant Vitex agnus-castus (VAC) extract on isolated rabbit arterial rings. The VAC extracts (VACE) were extracted with ethanol and tested in aorta rings (3-4 mm) of rabbits suspended in an organ bath (Krebs, 37°C, 95% O₂/5% CO₂) under a resting tension of 1 g to record isometric contractions. After the stabilization period (1-2 hours), contractions were induced by the addition of phenylephrine (0.5 μM) or high KCl (80 mM) and VACE was added on the plateau of the contractions. Experiments were performed to determine the effects and to get insights into the potential mechanism involved in VACE-induced relaxations. The cumulative addition of VACE (0.15–0.75 mg/mL) relaxed, in a concentration-dependent manner, the rabbit aorta rings precontracted either with phenylephrine- or with high KCl thus suggesting calcium channel blocking activities. The VACE effect appeared to be endothelium-dependent. The preincubation with L-NAME (the inhibitor of nitric oxide synthases (NOS)), ODQ (the selective inhibitor of guanylyl cyclase), and indomethacin (the cyclooxygenase inhibitor), downregulated VACE-induced relaxation of aorta rings precontracted with phenylephrine, whereas the bradykinin (stimulator of NOS) and zaprinast (phosphodiesterase inhibitor) further upregulated relaxant effects induced by VACE. These results revealed that the aorta relaxation effect of VACE was mainly endothelium-dependent and mediated by NO/cGMP and prostaglandins synthesis. This vasodilator effect of VACE may be useful to treat cardiovascular disorders, including hypertensive diseases.