N-Hydroxycinnamoyl amides of fluorinated amino acids: Synthesis, anti-tyrosinase and DPPH scavenging activities

A tiered approach for evaluation of anti-melanogenic activity of trans-N-coumaroyltyramine derivatives

Skin hyperpigmentation is commonly treated by topical drug application. Several naturally occurring compounds exhibit attractive biological effects including anti-melanogenic activity. Chemically modified derivatives of those compounds are expected to be more efficient. However, efficacy and safety testing processes are of significant consideration to identify the most effective compound among them. Herein, we demonstrated a tiered approach to investigate the antipigmentation activity of 17 trans-N-coumaroyltyramine derivatives. First, we evaluated the in chemico antityrosinase activity, then the cytotoxicity of the most potent derivatives using a mitochondrial activity-based assay, followed with the in vitro anti-melanogenic activity in two dimensional (2D) monolayer human melanocytes. The selected derivatives were topically applied on a three dimensional (3D) pigmented-reconstructed human epidermis (pRhE) containing melanocytes and keratinocytes to evaluate their depigmenting activity. Two of the 17 derivatives displayed a significant reduction in pigmentation in the 3D pRhE, comparable to kojic acid, a known tyrosinase inhibitor. In addition, a molecular docking experiment indicated an interaction of the three derivatives and tyrosinase, suggesting that these derivatives have potent anti-melanogenic activity through tyrosinase inhibition. Our findings provide an alternative approach for investigating skin-whitening agents, thereby facilitating the research and development of skin-whitening products that need not be tested on animals.

Synthesis, Photoisomerization, Antioxidant Activity, and Lipid-Lowering Effect of Ferulic Acid and Feruloyl Amides

The Ugi four-component reaction employing naturally occurred ferulic acid (FA) is proposed as a convenient method to synthesize feruloyl tertiary amides. Applying this strategy, a peptoid-like derivative of ferulic acid (FEF77) containing 2 additional hydroxy-substituted aryl groups, has been synthesized. The influence of the configuration of the double bond of ferulic acid and feruloyl amide on the antioxidant activity has been investigated thanks to light-mediated isomerization studies. At the cellular level, both FA, trans and cis isomers of FEF77 were able to protect human endothelial cord vein (HECV) cells from the oxidative damage induced by exposure to hydrogen peroxide, as measured by cell viability and ROS production assays. Moreover, in steatotic FaO rat hepatoma cells, an in vitro model resembling non-alcoholic fatty liver disease (NAFLD), the molecules exhibited a lipid-lowering effect, which, along with the antioxidant properties, points to consider feruloyl amides for further investigations in a therapeutic perspective.

Synthesis of readily available fluorophenylalanine derivatives and investigation of their biological activity

A series of thirty novel N-acetylated fluorophenylalanine-based aromatic amides and esters was synthesized using N-(3-dimethylaminopropyl)-N'-ethylcarbodiimide or phosphorus trichloride in pyridine. They were characterized by spectral methods and screened against various microbes (Mycobacterium tuberculosis, non-tuberculous mycobacteria, other bacteria, fungi), for their inhibition of acetylcholinesterase (AChE) and butyrylcholinesterase (BChE) and cytotoxicity. All amino acids derivatives revealed a moderate inhibition of both cholinesterases with IC₅₀ values for AChE and BChE of 57.88-130.75µM and 8.25-289.0µM, respectively. Some derivatives were comparable or superior to rivastigmine, an established drug. Phenyl 2-acetamido-3-(4-fluorophenyl)propanoate was identified as the selective and most potent inhibitor of BChE. The esterification and amidation of parent acids led to an improved BChE inhibition. The esters are better inhibitors of BChE than the amides. The introduction of NO₂ and CH₃ groups into aniline ring and CF₃ moiety in phenol is translated into lower IC₅₀ values. Seven compounds showed selectivity index higher than 10 for at least one cholinesterase. Especially the esters exhibited a mild activity against Gram-positive bacteria, mycobacteria and several fungal strains with minimum inhibitory concentrations starting from 125µM. The highest susceptibility was recorded for Trichophyton mentagrophytes fungus.

Hydroxycinnamic Acids and Their Derivatives: Cosmeceutical Significance, Challenges and Future Perspectives, a Review

Bioactive compounds from natural sources, due to their widely-recognized benefits, have been exploited as cosmeceutical ingredients. Among them, phenolic acids emerge with a very interesting potential. In this context, this review analyzes hydroxycinnamic acids and their derivatives as multifunctional ingredients for topical application, as well as the limitations associated with their use in cosmetic formulations. Hydroxycinnamic acids and their derivatives display antioxidant, anti-collagenase, anti-inflammatory, antimicrobial and anti-tyrosinase activities, as well as ultraviolet (UV) protective effects, suggesting that they can be exploited as anti-aging and anti-inflammatory agents, preservatives and hyperpigmentation-correcting ingredients. Due to their poor stability, easy degradation and oxidation, microencapsulation techniques have been employed for topical application, preventing them from degradation and enabling a sustained release. Based on the above findings, hydroxycinnamic acids present high cosmetic potential, but studies addressing the validation of their benefits in cosmetic formulations are still scarce. Furthermore, studies dealing with skin permeation are scarcely available and need to be conducted in order to predict the topical bioavailability of these compounds after application.

Rhodotorula glutinis Phenylalanine/Tyrosine Ammonia Lyase Enzyme Catalyzed Synthesis of the Methyl Ester of para-Hydroxycinnamic Acid and its Potential Antibacterial Activity

Biotransformation of L-tyrosine methyl ester (L-TM) to the methyl ester of para- hydroxycinnamic acid (p-HCAM) using Rhodotorula glutinis yeast phenylalanine/tyrosine ammonia lyase (PTAL; EC 4.3.1.26) enzyme was successfully demonstrated for the first time; progress of the reaction was followed by spectrophotometric determination at 315 nm. The following conditions were optimized for maximal formation of p-HCAM: pH (8.5), temperature (37°C), speed of agitation (50 rpm), enzyme concentration (0.080 μM), and substrate concentration (0.50 mM). Under these conditions, the yield of the reaction was ∼15% in 1 h incubation period and ∼63% after an overnight (∼18 h) incubation period. The product (p-HCAM) of the reaction of PTAL with L-TM was confirmed using Nuclear Magnetic Resonance spectroscopy (NMR). Fourier Transform Infra-Red spectroscopy (FTIR) was carried out to rule out potential hydrolysis of p-HCAM during overnight incubation. Potential antibacterial activity of p-HCAM was tested against several strains of Gram-positive and Gram-negative bacteria. This study describes a synthetically useful transformation, and could have future clinical and industrial applications.

Design and discovery of mushroom tyrosinase inhibitors and their therapeutic applications

INTRODUCTION

Tyrosinase inhibitors could have a huge importance in medicine, cosmetics and agriculture. Although many tyrosinase inhibitors are available, they have demonstrated only mild efficacy and safety concerns. This has led to the discovery of novel tyrosinase inhibitors that are more safe, potent and efficacious.

AREAS COVERED

The authors provide an overview of the recent scientific accounts describing the design of new molecules. These compounds belong to different chemical families. The review emphasizes the rationale behind the discovery, the study of structure-activity relationships, the study of the mechanism and kinetic of inhibition and the cellular effect of the inhibitors. The article is based on the literature published from 2007 onward related with the development of synthetic tyrosinase inhibitors.

EXPERT OPINION

Although a great number of tyrosinase inhibitors have been published in the literature, none, as of yet, have reached the potency and safety requirements needed to enter clinical trials. The emergence of new in vitro and in vivo tests will finally allow the arrival of new compounds that are more potent and safe.

Chemical composition and biological activities of Gerbera anandria

Gerbera anandria (Compositae) was extracted with 75% ethanol and the residue was fractionated using light petroleum, chloroform and ethyl acetate. The constituents of the extracts were separated by column chromatography employing solvents of different polarity. Column chromatography of the light petroleum fraction resulted in the isolation of methyl hexadecanoate, while the chloroform fraction afforded xanthotoxin, 2-hydroxy-6-methylbenzoic acid, 7-hydroxy-1(3H)-isobenzofuranone, a mixture of β-sitosterol and stigmasterol, and 8-methoxysmyrindiol and the ethyl acetate fraction gave gerberinside, apigenin-7-O-β-d-glucopyranoside and quercetin. A new coumarin, 8-methoxysmyrindiol, was found. The chemical structures of the isolated compounds were established by MS and NMR (HSQC, HMBC). Free radical scavenging and cytotoxic activities of crude extracts and 8-methoxysmyrindiol were further investigated. The ethyl acetate phase exerted the strongest DPPH free radical scavenging activity in comparison to the other fractions. The coumarin 8-methoxysmyrindiol demonstrated cytotoxicity against multiple human cancer cell lines, with the highest potency in HepG2 cells.