Tyrosinase Inhibitory Activity of Total Triterpenes and Poricoic Acid A Isolated from Poria cocos

Novel Tripeptides as Tyrosinase Inhibitors: In Silico and In Vitro Approaches

Tyrosinase is a key enzyme responsible for the formation of melanin (a natural skin pigment with ultraviolet-protection properties). However, some people experience melanin overproduction, so new, safe, and biocompatible enzyme inhibitors are sought. New tripeptide tyrosinase inhibitors were developed using molecular modeling. A combinatorial library of tripeptides was prepared and docked to the mushroom tyrosinase crystal structure and investigated with molecular dynamics. Based on the results of calculations and expert knowledge, the three potentially most active peptides (CSF, CSN, CVL) were selected. Their in vitro properties were examined, and they achieved half-maximal inhibitory concentration (IC50) values of 136.04, 177.74, and 261.79 µM, respectively. These compounds attach to the binding pocket of tyrosinase mainly through hydrogen bonds and salt bridges. Molecular dynamics simulations demonstrated the stability of the peptid-tyrosinase complexes and highlighted the persistence of key interactions throughout the simulation period. The ability of these peptides to complex copper ions was also confirmed. The CSF peptide showed the highest chelating activity with copper. The 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) assay confirmed that none of the test tripeptides showed cytotoxicity toward the reconstructed human epidermis. Our results indicated that the developed tripeptides were non-toxic and effective tyrosinase inhibitors. They could be applied as raw materials in skin-brightening or anti-aging cosmetic products.

Anti-tyrosinase and anti-melanogenic effects of piperine isolated from Piper nigrum on B16F10 mouse melanoma cells

The essential function of melanin is to protect our skin against harmful environmental factors. However, excessive melanin production can cause undesirable hyperpigmentation issues, such as freckles and melasma. Although several compounds are used to control melanin production by inhibiting tyrosinase (TYR), their efficacy is limited by skin-related adverse effects and cytotoxicity concerns. Consequently, searching for new natural compounds with an effective TYR inhibitor (TYR-I) activity but less harmful effects continues. Plant-based natural extracts are an alternative that are in great demand due to their safety and diverse biological properties. This study assessed ten isolated plant compounds for their TYR-I activities using an in vitro mushroom TYR inhibition assay. Among these compounds, piperine (400 μM) demonstrated the highest TYR-I activity, with a potency of 36.27 ± 1.96 %. Hence, this study examined the effect of piperine on melanogenesis in melanocyte stimulating hormone-treated B16F10 melanoma cells and using kojic acid as a positive reference. Cell viability was evaluated through the standard 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide assay. Measurements of cellular TYR activity and melanin content were performed and related to changes in the transcriptional expression levels of melanogenesis-related genes, assessed via quantitative real-time reverse transcriptase (RT-q)PCR analysis. The results revealed that piperine at a concentration of 44 μM significantly reduced cellular TYR activity by 21.51 ± 2.00 % without causing cytotoxicity. Additionally, at the same concentration, piperine significantly decreased the intracellular melanin content by 37.52 ± 2.53 % through downregulating transcription levels of TYR and TYR-related protein 1 (TRP-1) but not TRP-2. Kojic acid, at a concentration of 1407 μM, induced a significant decrease in the melanin content and cellular TYR activity by suppressing all three melanogenesis-related genes. These findings suggest that piperine has potential as a potent depigmenting agent.

Identification of squalene epoxidase in triterpenes biosynthesis in Poria cocos by molecular docking and CRISPR-Cas9 gene editing

BACKGROUND

Squalene epoxidase is one of the rate-limiting enzymes in the biosynthetic pathway of membrane sterols and triterpenoids. The enzyme catalyzes the formation of oxidized squalene, which is a common precursor of sterols and triterpenoids.

RESULT

In this study, the squalene epoxidase gene (PcSE) was evaluated in Poria cocos. Molecular docking between PcSE and squalene was performed and the active amino acids were identified. The sgRNA were designed based on the active site residues. The effect on triterpene synthesis in P. cocos was consistent with the results from ultra-high-performance liquid chromatography-quadruplex time-of-flight-double mass spectrometry (UHPLC-QTOF-MS/MS) analysis. The results showed that deletion of PcSE inhibited triterpene synthesis. In vivo verification of PcSE function was performed using a PEG-mediated protoplast transformation approach.

CONCLUSION

The findings from this study provide a foundation for further studies on heterologous biosynthesis of P. cocos secondary metabolites.

Phytochemistry and Biological Activities of Poria

Poria is a common Traditional Chinese Medicine in clinic. In recent years, the chemical and pharmacological studies of Poria have made great progress, triterpenes and polysaccharides have been isolated, and various types of compounds containing lipids, octanoic acids, fatty acids, and trace elements have been found. In this paper, we reviewed the literature, summarized the main compound types, and reviewed in detail their pharmacological effects in antitumor, immunomodulatory, effects on kidney, hepatoprotective activity, effects on blood sugar, antioxidant effects, anti-inflammatory effects, effects on the gut, antidepressant, and so on, and also categorized the compounds with the same or similar pharmacological effects to provide a reference for the in-depth study of the material basis of the pharmacological effect, quality standards, and pharmacological activity of Poria.

5-Methoxy-2-mercaptobenzimidazole as an efficient inhibitor on tyrosinase: Inhibitory activity and mechanism

In this study, 5-methoxy-2-mercaptobenzimidazole (5-M-2-MB) was confirmed as an efficient tyrosinase inhibitor by methods of enzyme kinetic, fluorescence quenching, ANS-binding, thermodynamics, energy transfer, and molecular docking in combination. The results proved that 5-M-2-MB significantly inhibited the tyrosinase (IC₅₀ = 60 ± 2 nM) in a reversible and competitive way with the K_i value of 80 ± 1 nM. It quenched the intrinsic fluorescence of tyrosinase through a static mechanism, and caused conformational change of the enzyme by increasing the hydrophobic region. Moreover, this compound could bind to tyrosinase and form 5-M-2-MB-tyrosinase complex by hydrogen bond and hydrophobic interaction. The interactions were generated between 5-M-2-MB and specific amino acid residues (Trp-358, Thr-308, Glu-356, and Asp-357) located on the A chain of tyrosinase. Therefore, this study would offer a theoretical foundation for developing the new tyrosinase inhibitor.

Transdermal Delivery Systems of Natural Products Applied to Skin Therapy and Care

Natural products are favored because of their non-toxicity, low irritants, and market reacceptance. We collected examples, according to ancient wisdom, of natural products to be applied in transdermal delivery. A transdermal delivery system, including different types of agents, such as ointments, patches, and gels, has long been used for skin concerns. In recent years, many novel transdermal applications, such as nanoemulsions, liposomes, lipid nanoparticles, and microneedles, have been reported. Nanosized drug delivery systems are widely applied in natural product deliveries. Nanosized materials notably enhance bioavailability and solubility, and are reported to improve the transdermal permeation of many substances compared with conventional topical formulations. Natural products have been made into nanosized biomaterials in order to enhance the penetration effect. Before introducing the novel transdermal applications of natural products, we present traditional methods within this article. The descriptions of novel transdermal applications are classified into three parts: liposomes, emulsions, and lipid nanoparticles. Each section describes cases that are related to promising natural product transdermal use. Finally, we summarize the outcomes of various studies on novel transdermal agents applied to skin treatments.

Anti-tyrosinase, anti-cholinesterase and cytotoxic activities of extracts and phytochemicals from the Tunisian Citharexylum spinosum L.: Molecular docking and SAR analysis

Previously phytochemical investigations carried out on the flowers and trunk bark extracts of Citharexylum spinosum L. tree, allowed the isolation of twenty molecules belonging to several families of natural substances [triterpene acids, iridoid glycosides, phenylethanoid glycosides, 8,3'-neolignan glycosides, together with other phenolic compounds]. In the present work, a biological evaluation (anti-tyrosinase, anticholinesterase and cytotoxic activities) was performed on the prepared extracts and the isolated secondary metabolites. The results showed that the EtOAc extract of the trunk bark displayed the highest anti-tyrosinase effect with a percent inhibition of 55.0 ± 1.8% at a concentration of 100 µg/mL. The highest anticholinesterase activity was presented by the same extract with an IC₅₀ value of 99.97 ± 3.01 µg/mL. The EtOAc extract of flowers and that of the trunk bark displayed the best cytotoxic property with IC₅₀ values of 96.00 ± 2.85 and 88.75 ± 2.00 µg/mL, respectively, against the human cervical cancer cell line (HeLa), and IC₅₀ values of 188.23 ± 3.88 and 197.00 ± 4.25 µg/mL, respectively, against the human lung cancer (A549) cell lines. Biological investigation of the pure compounds showed that the two 8,3'-neolignan glycosides, plucheosides D₁-D₂, generate the highest anti-tyrosinase potency with a percent inhibition of 61.4 ± 2.0 and 79.5 ± 2.3%, respectively, at a concentration of 100 µM. The iridoid glycosides exhibited a significant anticholinesterase activity with IC₅₀ values ranging from 17.19 ± 1.02 to 52.24 ± 2.50 µM. Triterpene pentacyclic acids and iridoid glycosides exerted encouraging cytotoxic effects against HeLa with IC₅₀ values ranging from 9.00 ± 1.10 to 25.00 ± 1.00 µM. The study of the structure-activity relationship (SAR) has been sufficiently and widely discussed. The natural compounds that exhibited the significant bioactivities were docked.

The Role of Bioactive Compounds and other Metabolites from Mushrooms against Skin Disorders- A Systematic Review Assessing their Cosmeceutical and Nutricosmetic Outcomes

Bioactive compounds derived from mushrooms have been shown to present promising potential as cosmeceutical or nutricosmetic ingredients. Scientific data reviewed herein showed that extracts prepared from medicinal and edible mushrooms and their individual metabolites presented antiinflammatory, antioxidant, photoprotective, antimicrobial, anti-tyrosinase, anti-elastase, and anticollagenase activities. These metabolites can be utilised as ingredients to suppress the severity of Inflammatory Skin Diseases, offer photoprotection to the skin, and correct Hyperpigmentation. However, studies regarding the molecular mechanism behind the mentioned bioactivities are still lacking. Challenges associated with the use of mushroom extracts and their associated metabolites as cosmeceutical and nutricosmetic ingredients include several steps from the fruiting bodies to the final product: extraction optimization, estimation of the efficacy and safety claims, the use of micro and nanocarriers to allow for controlled release and the pros and cons associated with the use of extracts vs individual compounds. This systematic review highlights that mushrooms contain diverse biomolecules that can be sustainably used in the development of nutricosmetic and cosmeceutical formulations. Reports regarding stability, compatibility, and safety assessment, but also toxicological studies are still needed to be considered. Furthermore, some of the constraints and limitations hindering the development of this type of ingredients still require long-term studies to achieve major breakthroughs.