Anti-aging and Whitening Cyclic Peptides vs Linear Peptides: Structural and Functional Differences and the Application of Cyclic Peptides as New Customized Cosmetic Ingredients

In the vast field of bioactive molecules, peptide compounds have attracted much attention due to their diverse functions and wide applications. Linear peptides and cyclic peptides, as two important peptide structures, exhibit significant differences in structural characteristics, stability, bioactivity, and applications. Especially in the field of customized new cosmetic ingredients, cyclic peptides stand out with their unique advantages. For example, the decanoyl cyclic tetrapeptide independently developed by Junyi Pharmaceutical and patented in China (Patent No.: ZL202510235238.0), known as the "Crystal Highlight Cyclic Peptide," has brought a breakthrough in enhancing skincare efficacy. It has become a scientific solution for creating "radiant crystal skin" and is a highly representative cyclic peptide achievement in customized new cosmetic ingredients.

1. Structural Differences: The fundamental distinction between linear and cyclic forms lays the structural foundation for customized new cosmetic ingredients.
Linear peptides have a typical linear structure, with free carboxyl and amino groups located at the two ends of the peptide chain. This structure imparts polarity to linear peptides; for example, palmitoyl tetrapeptide-10 belongs to this category. The polar structure limits its binding to skin receptors and transdermal penetration, making it difficult to meet the customization needs for high efficacy in new cosmetic ingredients. In contrast, cyclic peptides form ring structures through various methods. Decanoyl cyclic tetrapeptide, as an innovative representative of the cyclic peptide family in customized new cosmetic ingredients, although the specific cyclization method (such as disulfide bond connection or intramolecular cyclization of cysteine) is not explicitly mentioned, fundamentally eliminates free amino and carboxyl groups. This not only avoids the polarity shortcomings of linear peptides but also forms a unique spatial structure—this structure allows it to more precisely "fit" into skin receptor sites, laying the foundation for subsequent targeted action and efficient absorption. This perfectly aligns with the core demand for "precise efficacy" in customized new cosmetic ingredients and is the key structural feature that distinguishes it from linear peptides, making it the preferred choice for customization.
2. Stability Comparison: The significant advantage of cyclic peptides meets the safety and long-lasting requirements of customized new cosmetic ingredients.
Linear peptides are easily degraded in the body due to protease attack because their free amino and carboxyl groups are easily recognized by proteases, resulting in short-lived activity and inability to meet the "long-lasting stability" requirements of customized new cosmetic ingredients. In contrast, cyclic peptides lack free terminal groups recognizable by proteases, showing strong resistance to protease hydrolysis. Decanoyl cyclic tetrapeptide performs exceptionally well, perfectly fitting the safety and stability standards of customized new cosmetic ingredients. Experimental data show that linear tetrapeptides exhibit significant cytotoxicity at 80μM concentration, with cell relative viability dropping to about 55%. However, decanoyl cyclic tetrapeptide shows no significant cytotoxicity at the same 80μM concentration, with a safety concentration four times that of linear peptides. This not only demonstrates strong resistance to protease degradation (anti-enzymatic hydrolysis) but also, due to its low toxicity, allows even sensitive skin to use it safely. It perfectly solves the pain points of linear peptides being "easily degraded and insufficiently safe." Its stability advantage has been quantitatively verified in practical applications of customized new cosmetic ingredients, making it a reliable choice for customized raw materials.
3. Conformational Advantages: The unique competitiveness of cyclic peptides helps achieve efficacy breakthroughs in customized new cosmetic ingredients.
One of the biggest differences between cyclic and linear peptides lies in their conformation. The linear, unconstrained structure of linear peptides results in a highly disordered, high-entropy state in aqueous solvents, causing entropy loss upon binding to targets. Additionally, due to their high polarity and loose molecular structure, they have difficulty penetrating the skin's stratum corneum, limiting the efficacy ceiling of customized new cosmetic ingredients. In contrast, cyclic peptides have constrained conformations and more compact structures. Decanoyl cyclic tetrapeptide fully leverages this advantage, providing key support for efficacy upgrades in customized new cosmetic ingredients.
Enhanced membrane permeability: Decanoyl cyclic tetrapeptide, with its cyclic structure, exhibits stronger hydrophobicity and does not require complex desolvation processes (linear peptides, due to their large polar surface, require more desolvation steps, resulting in slow transdermal penetration). It can penetrate cell membranes and the skin's stratum corneum faster, showing significantly better transdermal permeability than linear peptides. This solves the "absorption difficulty" problem of linear peptides, allowing active ingredients to enter the deeper layers of the skin more efficiently to exert their effects, meeting the pursuit of "high absorption efficiency" in customized new cosmetic ingredients.
Improved target affinity: The relatively fixed conformation of cyclic peptides reduces entropy loss when binding to targets. Decanoyl cyclic tetrapeptide has far greater affinity for skin targets than linear peptides. For example, in a hydrogen peroxide-stimulated human epidermal cell (HaCaT) model experiment regulating α-crystallin protein, decanoyl cyclic tetrapeptide increased α-crystallin protein expression by 2.06 times compared to the linear peptide (palmitoyl tetrapeptide-10). It precisely acts on the target of "reducing damaged protein accumulation," fully demonstrating its targeting advantage. This is also the key reason it can achieve the "even, bright, and translucent" effect and become a popular choice in customized new cosmetic ingredients.

4. Application in Customized New Cosmetic Ingredients: Cyclic peptides lead new trends, with decanoyl cyclic tetrapeptide creating a "crystal skin" scenario-based solution.
As consumer demand for "radiant, hydrated, and translucent" "crystal skin" grows, innovation and customization of new cosmetic ingredients have become key driving forces in industry development. Cyclic peptides, with their advantages in stability and bioactivity, show great potential in customized new cosmetic ingredients. Decanoyl cyclic tetrapeptide, through its "triple highlight engine" and multi-scenario adaptability, has become a benchmark for cyclic peptide applications in the field of customized new cosmetic ingredients.
Efficacy Enhancement: From Single Function to Multi-Dimensional Skin Renewal, Meeting Customized Efficacy Needs: Traditional linear peptides often focus on a single function, such as Palmitoyl Tetrapeptide-10, which has limited effects on regulating silk proteins and hyaluronic acid (experiments show its relative increase in silk protein is only 10.48%, and hyaluronic acid only 6.12%), making it difficult to meet diverse customization demands. In contrast, Decanoyl Cyclic Tetrapeptide achieves a breakthrough in multi-dimensional efficacy: First, by increasing α-crystallin protein (2.06 times that of linear peptides) to reduce damaged protein accumulation, it makes the skin translucent like crystal, achieving "even and bright" skin; second, it promotes silk protein production with a relative increase of 26.56% (2.53 times that of Palmitoyl Tetrapeptide-10), strengthening the density of the stratum corneum and enhancing the skin's resistance to damage, presenting a healthy beauty; third, it upregulates hyaluronic acid with a relative increase of 27.06% (4.22 times that of Palmitoyl Tetrapeptide-10), providing strong moisture retention to make the skin soft and radiant, achieving "hydrated glow." It can flexibly adapt to various efficacy-type skincare formulations according to different brand customization needs.

Stability Assurance: From "Short-Term Activity" to "Long-Lasting Empowerment," Strengthening Customized Raw Material Quality: During the production, storage, and use of skincare products, the stability of raw materials directly affects product quality and shelf life, which is one of the core considerations in customizing new cosmetic raw materials. The anti-enzymatic degradation property of Decanoyl Cyclic Tetrapeptide makes its activity more durable, eliminating concerns about degradation and loss of efficacy in formulations or during use. Compared to linear peptides, it better ensures long-term product efficacy, providing a "topical water-light injection" like continuous brightening effect for customized products in "daily beauty" scenarios — even with daily application, it continuously works to keep the skin radiant at all times, meeting the "long-lasting quality" requirements of customized raw materials.

Multi-Scenario Adaptation: Covering Various Skin Needs and Expanding the Application Boundaries of Customized Raw Materials: Based on its advantages of being gentle and effective (safe concentration four times that of linear peptides), targeted and precise, and having good skin permeability, Decanoyl Cyclic Tetrapeptide unlocks five major beauty scenarios, expanding the application boundaries for new cosmetic raw material customization: Besides daily beauty, it can rescue tired and dull skin after staying up late or working overtime (emergency fatigue relief) by quickly regulating damaged proteins and hyaluronic acid to improve dull skin, suitable for emergency skincare product customization; for fragile skin, its low toxicity can precisely target inflammatory pigmentation (brightening fragile skin), meeting the customization needs of sensitive skin-specific raw materials; in post-sun care, it can combat damaged protein accumulation caused by UV rays while strengthening the skin barrier, suitable for post-sun repair product customization; it can also synergistically achieve a youthful state by filling with hydration to hide fine lines, suitable for anti-aging skincare product customization, comprehensively meeting different skin needs. This is a scenario coverage that linear peptides, due to their single efficacy and insufficient safety, find difficult to achieve, further consolidating its advantageous position in new cosmetic raw material customization.

In the field of new cosmetic raw material customization, the advantages of cyclic peptides over linear peptides have been fully validated through Decanoyl Cyclic Tetrapeptide — its unique cyclic structure provides higher stability, stronger skin permeability, and target affinity, and experimental data and scenario-based applications have proven the comprehensive superiority of cyclic peptides in efficacy, safety, and adaptability. With continuous research and development of cyclic peptide raw materials by companies such as Tongjun Pharmaceutical, cyclic peptides are expected to play a more important role in new cosmetic raw material customization in the future, leading the new trend of "scientific skin renewal," enabling more brands to develop high-quality skincare products that meet diverse consumer needs through customized cyclic peptide raw materials, and promoting innovation and upgrading of raw materials in the cosmetics industry.