Kojic acid (KA) has emerged as a prominent tyrosinase inhibitor with considerable potential in cosmetic applications; however, its susceptibility to instability during storage poses a challenge to its widespread use. This review explores the advancements in addressing this limitation through the development of various KA derivatives, focusing on the modification of the C-7 hydroxyl group. Strategies such as esterification, hydroxy-phenyl ether formation, glycosylation, and incorporation into amino acid or tripeptide derivatives have been employed to enhance stability and efficacy. Among these derivatives, Kojic Acid Dipalmitate (KDP), a palmitic ester derivative of KA, stands out for its notable improvements in stability, permeability, and low toxicity. Recent developments indicate a growing utilization of KDP in cosmetic formulations, with over 132 available products on the market, encompassing various formulations. Additionally, three patents and seven advanced system deliveries of KDP further underscore its significance. Despite its increasing prevalence, the literature on KDP remains limited. This comprehensive review aims to bridge this gap by providing insights into the synthesis process, physicochemical properties, pharmaceutical preparation, diverse applications of KDP in cosmetic products, and recent nanotechnology formulations of KDP. This review paper seeks to explore the recent developments in the use of KDP in cosmetics. The goal is to enhance stability, permeability, and reduce the toxicity of KA, with the intention of promoting future research in this promising sector.

DNA-binding transcription factors are broadly characterized as proteins that bind to specific sequences within genomic DNA and modulate the expression of downstream genes. This study focused on KojR—a transcription factor involved in the metabolism of kojic acid, which is an organic acid synthesized in Aspergillus oryzae and is known for its tyrosinase-inhibitory properties. However, the regulatory mechanism underlying KojR-mediated kojic acid synthesis in remains unclear. Hence, we aimed to obtain a comprehensive identification of KojR-associated genes using genomic Systematic Evolution of Ligands by Exponential enrichment (gSELEX-Seq) and RNA-Seq. During the genome-wide exploration of KojR-binding sites via gSELEX-Seq and identification of KojR-dependent differentially expressed genes (DEGs) using RNA-Seq, we confirmed that KojR directly regulates kojT, as was previously reported. We also observed that kojA expression, which may be controlled by KojR, was significantly reduced in a ΔkojR strain. Notably, no binding of KojR to the kojA promoter region was detected. Furthermore, certain KojR-dependent DEGs identified in the present study were associated with enzymes implicated in the carbon metabolic pathway of A. oryzae. This strongly indicates that KojR plays a central role in carbon metabolism in A. oryzae.

The practice of voluntary depigmentation is still prevalent in Africa, with a wide range of lightening cosmetics used. Our objective was to research and quantify three regulated and/or prohibited depigmenting ingredients present in lightening cosmetics sold in Ouagadougou. Twenty-nine lightening cosmetic samples were collected from vendors and HPLC analysis was subsequently conducted to identify and measure the concentrations of hydroquinone, clobetasol propionate, and kojic acid. The presence of hydroquinone was indicated on the label of 13.79% of the products, while 51.72% contained it after analysis. Furthermore, none of the products mentioned a concentration of hydroquinone exceeding 2.00%, even though 27.58% of them contained high concentrations. For clobetasol propionate, its presence was stated on the labels of 13.79% of the products, while 31.03% contained it. One sample had a clobetasol content exceeding 0.05%, although none mentioned a concentration higher than this value. Finally, while 24.13% of the samples claimed to contain kojic acid, only 17.24% did. We also observed that 41.38% of the samples contained combinations of two depigmenting ingredients investigated, with a predominance of the hydroquinone + clobetasol propionate (27.38%). These results demonstrate that manufacturers' declarations regarding the compositions of active ingredients in lightening cosmetics can sometimes be deceptive.

Nowadays, there is evidence that bacteria can contribute to cancer formation and interfere with therapy by mediating its carcinogenesis and related infection. Moreover, it is acknowledged that microbial infections and antibiotic resistance represent severe economic and health risks to society. These facts have led to the developing of several new techniques for impeding crucial biological processes in microbial cells. One of these techniques centers on using metal-chelating agents, which can disrupt the microorganism's vital metal metabolism by obstructing metal uptake and bioavailability for critical reactions. Additionally, nanotechnology has made a wide range of nanomaterials available for possible uses in the antibacterial industry. This complex field is shaped by antimicrobial nanoparticles, also investigated as therapeutic and drug-delivery tools. Halloysite nanotubes (HNTs) are naturally occurring tubular clay nanomaterials consisting of aluminosilicate kaolin sheets rolled up several times. The aluminon and siloxane groups on the surface of HNTs facilitate the formation of hydrogen bonds with biomaterials on their surface. These properties make HNTs crucial in a wide range of applications, such as in environmental sciences, wastewater treatment, dye removal, nanoelectronics and nanocomposite fabrication, catalytic studies, coatings for glass or anti-corrosive coatings, cosmetics, flame retardants, stimulus-response, and in forensic sciences. This work aimed to produce an antibacterial material by combining the properties of halloysite nanotubes with the ability of kojic acid to chelate iron. Starting from kojic acid, a simple nucleophilic substitution involving the hydroxyl groups on the surface of the nanotubes was performed. The obtained material was characterized by IR and SEM, and its ability to chelate iron was evaluated. Finally, the capacity to load drugs such as resveratrol and curcumin was also evaluated by UV analysis. In this way, a new bio-based material that can be used as a drug carrier and antimicrobial was produced.