Peptides can generally be divided into two major categories: animal-derived peptides and plant-derived peptides.
Most products on the market that claim to contain “small-molecule peptides” are actually plant-derived peptides (plants do not contain collagen). These peptides have a single-chain, planar structure (such as soy isoflavones or genistein). Because their structural form and amino acid composition differ greatly from animal-derived peptides, which have a triple-helix 3D structure, they are not compatible with human skin, resulting in less effective functionality.
However, animal-derived peptides naturally have a larger molecular weight (typically above 3,000 Daltons), making them difficult for the skin to absorb directly, which remains a major challenge in current peptide technology.