Most biological and chemical reactions in nature are regulated by specific amino acid sequences. By transcribing the interacting peptide sequence, it can be induced to produce small fragments with stable activity. The application of the above small fragments in skin cell proliferation and differentiation, extracellular matrix synthesis, and pigmentation has good effects, which provides a good opportunity for the development of dermatology and skin care. Compared with macromolecular proteins, small molecular peptides have the advantages of high utilization rate, low immunogenicity, low synthesis cost, and low toxicity. They have outstanding anti-oxidation, skin tissue repair, and anti-bacterial infection effects in the cosmetics field.

As shown in Figure 1, small-molecule peptides mainly refer to active substances that combine small-molecular-weight amino acid sequences with the human body in various ways. Because small molecular peptides are specific to skin receptors, they can enhance skin permeability while maintaining good performance stability. Generally speaking, according to the number of amino acid residues, small molecule polypeptides can be directly called dipeptides and tripeptides, and the number of amino acid residues in small molecule polypeptides is about 2-50. Small molecule peptides have the excellent characteristics of extremely strong biological activity, high safety performance, diverse activities, controllable quality, good membrane absorption, clear efficacy, and clear sequence. They have relatively good effects on normal adult epidermal keratinocytes and skin fibroblasts. And it can effectively improve the survival rate of aging human epidermal cells and skin fibroblasts, stimulate the activity of skin tissues, and increase the activity of stromal cells. Furthermore, it promotes the synthesis of skin collagen, hyaluronic acid, glycosaminoglycan, elastin, and fibronectin, and maintains skin elasticity. It has relatively prominent application value in the cosmetics field.
Small molecular peptides extracted from animals and plants mainly refer to the extraction of small molecular peptides from marine molluscs, terrestrial animals, marine plants, and land plants. Study reported that Liu, et al. prepared an in vitro cell model made by artificially reared Eisenia vulgaris. Through cell resuscitation culture and subculture, the activity of LMWPEE of earthworm small molecule polypeptide extract was investigated. And it was applied to applied it to normal adult epidermal keratinocyte HEK to explore its effect on normal adult skin fibroblast HSF, and HSF secreting type I procollagen. Through research, it is concluded that the earthworm small molecule polypeptide extract with a mass concentration of 25 mg/L presents a dose-effect relationship with the promotion of normal adult skin fiber cell activity. In addition to animal-derived small molecule polypeptides, plant-derived small molecule polypeptides have a wide range of applications in the cosmetics industry. Relevant researchers used protein hydrolysis and dextran gel permeation chromatography to directly extract and separate active biological peptides from natural plants such as rice, sweet potato, wolfberry, black beans, mung beans, wheat germ, and tea seeds. For example, the small molecule peptides in mung bean are extracted by enzymatic hydrolysis and applied to the skin surface. It can be concluded that mung bean small molecule polypeptide not only has strong anti-oxidation activity, but also has good skin whitening effect. In addition, microbial peptides also have more prominent advantages in the cosmetics industry. Microbial peptides mainly refer to enzymatic hydrolysis products derived from some fungi or aquatic algae, such as spirulina small molecule peptides.
Small molecule polypeptides directly extracted from natural organisms or obtained by protease hydrolysis have disadvantages such as poor stability, short half-life, poor in vitro stability, and difficulty in improving purity, and cannot meet the requirements of precise development and manufacturing of cosmetics. In the development process in recent years, with the continuous advancement of the research process of small molecule peptides in cosmetics by related researchers, the methods of synthetic small molecule peptides such as chemical synthesis peptide library and biosynthetic molecule peptide library have also been continuously improved. Among them, the chemical synthetic peptide library is mainly based on amino acids. The peptide chain synthesis uses solid phase synthesis, liquid phase synthesis and other chemical synthesis methods. At the same time, some unnatural amino acids are added, and appropriate modification is performed, and finally a high-purity extract of small molecule polypeptides can be obtained. The solid-state synthesis of small peptides needs to be proceeded gradually from the carboxyl end to the amino end, and the overall product purification is less difficult. For example, related researchers have used FMDC solid-phase synthesis to chemically synthesize peptide sequences. And when using high performance liquid chromatography, it was purified, and an anti-β2GP1 neurotransmitter inhibitor peptide was obtained. Such peptides can inhibit the synthesis of SNARE receptors and the excessive release of bicholamine and acetylcholine in the skin. At the same time, according to the mechanism of botulinum toxin, it locally blocks the nerve transmission of muscle contraction information to promote the relaxation of the corners of the eyes, face, forehead and other muscles, and finally achieves the purpose of wrinkle removal and fine lines; while the liquid phase synthesis method mainly uses mixed condensation reagents to synthesize peptides substance.
To be continued in Part II…
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