Seed watermelon extract found to promote sebum synthesis

A research group led by Associate Professor Tomohiro Itoh from the Graduate School of Bioresources at Mie University, Professor Takashi Fukuda from the Department of Fisheries in the Faculty of Agriculture at Kindai University, and Hagihara Farm Co., Ltd. (Shiki-gun, Nara Prefecture) announced on November 11 their discovery that coniferyl alcohol isolated from seed watermelon promotes sebum synthesis in the human sebaceous gland cell line SZ95 cells. The cultivar was developed by Hagihara Farm. The team found that coniferyl alcohol is a natural compound that promotes sebum synthesis and may improve skin barrier function. They plan to develop it for use as a cosmetic ingredient. Their findings were published in Molecules on August 2.

Dry skin is not simply a lack of moisture, but a physiological abnormality accompanied by a reduced skin barrier function. When sebum secretion decreases due to aging or stress, the skin membrane weakens, leading to a vicious cycle of moisture evaporation and inflammation. The skin barrier consists of corneocytes, intercellular lipids of the stratum corneum, and the sebum film. Among these components, ceramides and other substances form the sebum film. These are essential for maintaining barrier function.

In China, there is a watermelon cultivar bred for its seeds, which are eaten like nuts, known as "dagua." The seed watermelon cultivar used in this study was independently developed by Hagihara Farm and has characteristics found in wild varieties, including white flesh, unsweetened flesh, relatively large seeds, and drought tolerance.

In this study, the researchers isolated monolignols (coniferin, p-coumaryl alcohol, and coniferyl alcohol) from this cultivar. These compounds are synthesized using phenylalanine and tyrosine as substrates. The research team then examined the effects on sebum synthesis promotion in human sebaceous gland cells stimulated with linoleic acid by visualizing lipid accumulation using Oil Red O staining.

As a result, they confirmed that the isolated coniferyl alcohol promotes sebum synthesis in a dose-dependent manner. The quantity and enlargement of lipid droplets were also confirmed through microscopic observation.

Additionally, lipidomic analyses were conducted to comprehensively detect and quantify diverse lipid molecules present in living organisms. This further reveals metabolic states and disease mechanisms based on their composition and changes. These analyses showed a significant increase in lipid content containing linoleic acid as a constituent among the quantified lipid components.

It was inferred that coniferyl alcohol enhances the uptake of linoleic acid, a raw material for sebum synthesis, and uses it for sebum synthesis.

Future research is expected to clarify the molecular mechanism of action of coniferyl alcohol and assess its potential for use in topical formulations and supplements.

Itoh commented: "Initially, I started this research with my students hoping to find a sebum synthesis-inhibiting function that might help reduce acne in young people, but I was surprised to find the completely opposite effect of promoting sebum production. However, knowing that sebum synthesis capacity decreases in the dry skin of older individuals, I believe these results could be put to beneficial use. Going forward, I want to investigate the mechanism by which coniferyl alcohol, the active compound, promotes sebum synthesis, and verify whether topical application at the animal level can also confirm the sebum synthesis-promoting effect."

Journal Information
Publication: Molecules
Title: Seed Watermelon (Citrullus mucosospermus (Fursa))-Derived Coniferyl Alcohol as a Functional Ingredient in Remedies for Dry Skin: Evidence of Facilitated Lipogenesis in Human Sebocytes
DOI: 10.3390/molecules30163360