Phytochemical characterization and anti-inflammatory activity of a water extract of Gentiana purpurea roots

Biflavonoids and bi- and tricoumarins from Daphne mezereum and inhibition of TNF-α secretion

Daphne mezereum L. (Thymelaeaceae) was an important medicinal plant in Norway during the 18th and 19th centuries and used against diseases such as diarrhea, swelling, stomach pain, and tuberculosis. Five previously undescribed phenolic compounds, including two biflavonoids with a catechin core structure, two tricoumarins, and one bicoumarin, together with ten known compounds were isolated from a 50% EtOH extract of the bark of D. mezereum. Using NMR, HRESIMS, acid hydrolysis, and circular dichroism spectra, the biflavonoids were identified as 3'-hydroxygenkwanol A and 3'-hydroxydihydrodaphnodorin B, and the coumarins were identified as 3‴-O-acetyltriumbellin, triumbellin 4‴-O-β-d-glucopyranoside, and daphnogitin-7-O-β-d-glucopyranoside. The absolute configuration of dihydrodaphnodorin B was for the first time established as 2R, 3S, 2″S, 3″S. Daphnin, syringin, 3'-hydroxydihydrodaphnodorin B, dihydrodaphnodorin B, and neochamaejasmin A and B were identified as the major secondary metabolites in the extract. Neochamaejasmin A and B showed the most potent inhibition of TNF-α secretion in Con A stimulated peripheral blood mononuclear cells (PBMCs) with 71.3 ± 3.4 and 83.5 ± 11.5% inhibition, respectively, at 50 μM.

Unveiling the tyrosinase inhibitory potential of phenolics from Centaurium spicatum: Bridging in silico and in vitro perspectives

Phenolics, abundant in plants, constitute a significant portion of phytoconstituents consumed in the human diet. The phytochemical screening of the aerial parts of Centaurium spicatum led to the isolation of five phenolics. The anti-tyrosinase activities of the isolated compounds were assessed through a combination of in vitro experiments and multiple in silico approaches. Docking and molecular dynamics (MD) simulation techniques were utilized to figure out the binding interactions of the isolated phytochemicals with tyrosinase. The findings from molecular docking analysis revealed that the isolated phenolics were able to bind effectively to tyrosinase and potentially inhibit substrate binding, consequently diminishing the catalytic activity of tyrosinase. Among isolated compounds, cichoric acid displayed the lowest binding energy and the highest extent of polar interactions with the target enzyme. Analysis of MD simulation trajectories indicated that equilibrium was reached within 30 ns for all complexes of tyrosinase with the isolated phenolics. Among the five ligands studied, cichoric acid exhibited the lowest interaction energies, rendering its complex with tyrosinase the most stable. Considering these collective findings, cichoric acid emerges as a promising candidate for the design and development of a potential tyrosinase inhibitor. Furthermore, the in vitro anti-tyrosinase activity assay unveiled significant variations among the isolated compounds. Notably, cichoric acid exhibited the most potent inhibitory effect, as evidenced by the lowest IC50 value (7.92 ± 1.32 µg/ml), followed by isorhamnetin and gentiopicrin. In contrast, sinapic acid demonstrated the least inhibitory activity against tyrosinase, with the highest IC50 value. Moreover, cichoric acid exhibited a mixed inhibition mode against the hydrolysis of l-DOPA catalyzed by tyrosinase, with Ki value of 1.64. Remarkably, these experimental findings align well with the outcomes of docking and MD simulations, underscoring the consistency and reliability of our computational predictions with the actual inhibitory potential observed in vitro.

Analysis of bitter compounds in traditional preparations of Gentiana purpurea L

Roots of Gentiana purpurea are known to have an intense bitter taste due to its high content of secoiridoids. In folk medicine roots have commonly been prepared as water decoctions, soaked in ethanol, or boiled with milk, wine, or beer. The aim of this study was to explore how various historical preparation methods influence yields of major bitter compounds in G. purpurea. HPLC-DAD analysis revealed that maceration with 40% and 70% ethanol, boiling with acetic acid (3% and 6%), vinegar and raw milk gave the highest extraction yields of gentiopicrin. Erythrocentaurin was detected when the roots were added to cold water before boiling, possibly because of enzymatic degradation. In contrast, erythrocentaurin was not detected in preparations where roots were added to boiling water, or when they were extracted with acetic acid or alcohol. The results stress the significance of traditional preparation methods to optimize yield of bioactive compounds.

Bitter Phytochemicals as Novel Candidates for Skin Disease Treatment

Skin diseases represent a global healthcare challenge due to their rising incidence and substantial socio-economic burden. While biological, immunological, and targeted therapies have brought a revolution in improving quality of life and survival rates for certain dermatological conditions, there remains a stringent demand for new remedies. Nature has long served as an inspiration for drug development. Recent studies have identified bitter taste receptors (TAS2Rs) in both skin cell lines and human skin. Additionally, bitter natural compounds have shown promising benefits in addressing skin aging, wound healing, inflammatory skin conditions, and even skin cancer. Thus, TAS2Rs may represent a promising target in all these processes. In this review, we summarize evidence supporting the presence of TAS2Rs in the skin and emphasize their potential as drug targets for addressing skin aging, wound healing, inflammatory skin conditions, and skin carcinogenesis. To our knowledge, this is a pioneering work in connecting information on TAS2Rs expression in skin and skin cells with the impact of bitter phytochemicals on various beneficial effects related to skin disorders.