Soy extracts are well known as medicinal and nutritional ingredients. The multiple benefits of soybean extracts for skincare range from skin lightening, extracellular matrix enhancement and delayed hair growth, to a protective effect from photodamage and possibly from skin cancer.
Rich in proteins STI, a Kunitz-type trypsin inhibitor, and BBI, the Bowman-Birk protease inhibitor.
SKIN WHITENING
Soybean-derived serine protease inhibitors and soybean extracts alter skin pigmentation. Its inhibition of the serine proteases was found to reduce the keratinocyte receptor Protease-Activated Receptor-2 (PAR-2) in keratinocyte-melanocyte activation and therefore to alter skin color. It inhibits the PAR-2 activation resulting in cytoskeletal and cell surface reorganization and reduced keratinocyte phagocytosis.
Soybean extracts also reduce pigment deposition in human skin and decreases the pigmentary level of human age spots.
EXTRACELLULAR MATRIX ENHANCEMENT
Soybean extracts enhance collagen and elastin synthesis and promote the correct assembly of new elastin fibers, providing complete protection and restoration of the dermal extracellular matrix. It also has elastase-inhibitory activities which protect existing elastin fibers from degradation, therefore providing anti-aging benefits such as reducing skin sagging and wrinkling.
Additionally, these extracts exhibited elastin-enhancement activities. It increases the elastin fibers network with an accompanying increase in elastin mRNA and desmosine content.
Therefore, soybean extracts increase the expression of elastin, elastin-accessory proteins, and collagen. Soybean extracts not only protect the extracellular matrix from degradation, but also induce collagen and elastin synthesis, and increase the total amount of stable, cross-linked elastin fibers.
REDUCTION OF HAIR GROWTH
Soybean extracts delay the hair cycle, reduce hair growth, reduce the length of the hair shafts with reduced hair follicles size revealed by the reduction in hair follicle dimensions and hair bulb diameter. It results in thinner and smaller hair shafts. As a result, it reduced hair growth and led to a uniform, directionally organized hair appearance.
Additionally, the depigmenting effect of STI and BBI, soybean extract active component, led to lighter colored hair shafts, which could potentially contribute to the reduced visibility of undesired hair growth. Therefore, it alters the pattern of melanogenic gene expression.
PROTECTIVE EFFECT FROM PHOTODAMAGE
Soybean extracts reduce UV-induced edema and erythema and additionally reduces UVB-induced DNA and cellular damage, which could lessen the risk of skin cancer.
Soybean extracts inhibit the COX-2 pathway. It reduced UVB-induced COX-2 expression and PGE2 secretion and inhibited p38 MAP kinase activation. The COX-2 inhibitory activity of soybean extracts suggests the possible delay of photoaging and skin cancer processes in human skin.
Soy extract is safe to be used in cosmetic practice based on the concentrations specified in this safety assessment.
https://online.personalcarecouncil.org/ctfa-static/online/lists/cir-pdfs/FR784.pdf