Natural bioactive compounds play an increasingly important role in modern cosmetic formulations, particularly in the context of efficacy, safety, and regulatory compliance. Among them, vitamin A-related compounds have attracted significant attention due to their well-documented effects on skin renewal, collagen synthesis, and photoaging prevention. This review provides a comprehensive overview of natural vitamin A derivatives and structurally related carotenoids used in cosmetic applications, including retinol, retinal, retinyl esters, β-carotene, lycopene, zeaxanthin, astaxanthin, lutein, and fucoxanthin. The article critically examines their intracellular mechanisms of action, distinguishing between canonical retinoid signaling pathways mediated by nuclear receptors (RAR/RXR) and the predominantly antioxidant activities of carotenoids. Particular attention is given to the metabolic conversion of provitamin A compounds and their relevance to biological activity in the skin. Furthermore, recent regulatory restrictions on the use of retinol and retinyl esters, especially within the European Union, are discussed in the context of formulation challenges and the growing interest in naturally derived alternatives. By integrating mechanistic insights with regulatory and application-oriented perspectives, this review highlights the potential and limitations of natural vitamin A-related compounds and outlines future directions for their use in safe and effective cosmetic products.

The global rise of antimicrobial resistance represents a major challenge to public health and highlights the urgent need for the discovery of new antibacterial agents. Xanthones, characterized by a rigid dibenzo-γ-pyrone scaffold, have emerged as promising candidates owing to their broad structural diversity and ability to interact with multiple biological targets. This review provides examples of natural, semisynthetic, and synthetic xanthone derivatives investigated for their antimicrobial potential. Natural xanthones and their structural diversity are first discussed, followed by an analysis of semisynthetic and synthetic derivatives developed to overcome the structural limitations imposed by natural biosynthetic pathways and to improve antimicrobial activity. Particular attention is devoted to structure–activity relationships, including the effects of hydroxylation, methoxylation, alkylation, halogenation, and the position of substituents on antibacterial potency. The review further critically evaluates the factors that may limit the translation of promising in vitro findings into therapeutic applications, including limited mechanistic understanding, physicochemical properties, selectivity, toxicity, and the scarcity of standardized experimental approaches. Collectively, the available evidence supports xanthone derivatives as a valuable and versatile scaffold for the development of new antimicrobial candidates, while also highlighting the substantial work required to advance these compounds toward practical therapeutic applications.

The field of cosmetic science is rapidly evolving due to advances in skin biology research and increasing demand for evidence-based, personalized skincare solutions. A key aspect of this progress is the targeted modulation of biological macromolecules involved in skin aging, pigmentation, inflammation, and tissue regeneration. This review highlights major molecular targets in modern cosmetic research, focusing on telomerase, histone deacetylases (particularly sirtuins), matrix metalloproteinases, antioxidant enzymes, CD44 receptor, tyrosinase, microphthalmia-associated transcription factor, and melanocortin receptors, all of which regulate processes such as DNA repair, gene expression, extracellular matrix remodeling, and melanogenesis. Recent findings indicate that natural and synthetic compounds can effectively modulate these targets, supporting anti-aging and depigmenting strategies. Telomerase activators and sirtuin modulators show potential in maintaining cellular homeostasis and delaying skin aging. In pigmentation research, the transition from mushroom to human tyrosinase assays has enabled development of more selective inhibitors, including thiamidol. The review also addresses molecular targets relevant to inflammatory skin disorders, scars, and skin atrophy. Advances in molecular and biotechnological methods are expected to improve mechanistic understanding and support the rational design of safer, more effective next-generation cosmetic ingredients and formulations.