Skin aging is a multifactorial process involving genetic, environmental and hormonal factors. Current research has moved beyond wrinkle measurements to understand specific mechanistic paradigms, such as senescent aging (the accumulation of senescent cells), photoaging (UV-induced extracellular matrix degradation) and inflammatory aging (see Figure 1).
Figure 1. Factors that impact skin aging. Courtesy of Nattaya Lourith
These advances in scientific understanding have emerged at a time when the cosmetic landscape has shifted dramatically toward sustainable cosmetics, inspiring innovative approaches to upcycle ingredients that mitigate skin aging; food crop by-products are a good example.
Over the last decade, the number of studies has increased demonstrating that food phenolics such as ferulic acid from cereal can effectively treat skin aging.1 The potential of materials from other crops has also been highlighted.2 For example, caffeic, sinapic and rosmarinic acids – the prime phenolics in coffee, mustard and rosemary, and several vegetable and herb crops (see Figure 2) – have been identified as promising food phenolics for anti-aging benefits.3, 4
Figure 2. Prime phenolics found in coffee, mustard and rosemary. Courtesy of Nattaya Lourith
Accordingly, unlocking the power of these food phenolics to understand their potential for protecting skin and treating signs of aging aligns with the movement for sustainable beauty – as well as trends for natural beauty and beauty-from-within. In fact, the benefits of caffeic, sinapic and rosmarinic acids have more recently been uncovered, as described next.
This article reviews key aspects of skin aging, including senescence, photoaging and inflammation. It also provides an example of research exploring the potential of food phenolics to target these aspects.
Senescent Aging
As stated, skin aging is a complex process influenced by intrinsic and extrinsic factors. Among these, ultraviolet (UV) radiation and oxidative stress play pivotal roles by promoting inflammation and accelerating extracellular matrix (ECM) degradation. This, in turn, contributes to the formation of skin wrinkles – one of the most visible hallmarks of aging.
UVB radiation, consisting of shorter wavelengths, is primarily absorbed by the epidermis and directly affects keratinocytes, whereas UVA radiation penetrates more deeply into the skin, reaching both the epidermal and dermal layers and interacting predominantly with fibroblasts. These UV-induced effects stimulate the production of matrix metalloproteinases (MMPs), leading to the breakdown of key ECM components such as collagen and elastin.
The cumulative impact of aging, UV exposure, oxidative stress and inflammation further accelerates these degenerative processes, contributing to cellular senescence and progressive skin aging.5 Cellular senescence, in turn, contributes to tissue aging and the secretion of pro-inflammatory factors known as the senescence-associated secretory phenotype (SASP); subsequently, SASP can impact surrounding cells, perpetuating aging. Addressing senescent aging is thus a frontier in modern dermatology.
Figure 3. In vitro assessments of caffeic, sinapic and rosmarinic acids.Courtesy of Nattaya Lourith
To address senescent aging, in vitro assessments of the potency of caffeic, sinapic and rosmarinic acids to combat skin aging were carried out in a human dermal fibroblast (HDF) model. Caffeic, sinapic and rosmarinic acids (6.25-12.5 µg/mL) were not only found to be safe, but also capable of suppressing senescence-associated β-galactosidase (SA-β-gal) activity in HDF(see Figure 3). Among the phenolics tested, caffeic acid was identified as the most potent (see Figure 4).
Figure 4. Assessment of collagen synthesis and inhibition of MMP-1Courtesy of Nattaya Lourith
Moreover, the food phenolics stimulated cellular collagen synthesis in aged HDF while simultaneously down-regulating matrix metalloproteinase-1 (MMP-1; collagenase) and the cytokine interleukin-6 (IL-6). Researchers noted caffeic acid was the strongest collagen-stimulating agent, inhibiting MMP-1 and IL-6, followed by sinapic and rosmarinic acids (see Figure 4). The anti-senescent activities observed occurred in a dose-dependent manner.6
Taken together, critical pathways of skin aging were modulated by the food phenolics as evidenced accordingly.
Inflammatory Aging and Photoaging
Cellular senescence is progressively intensified by UV exposure since UV-induced oxidative stress exacerbates dermal damage through the upregulation of MMP – specifically MMP-1 and MMP-9 (gelatinase), the key enzymes responsible for extracellular matrix degradation.7 The resulting disrupted skin homeostasis triggers inflammatory responses that worsen cellular senescence and dermal tissue degradation. Chronic UV-induced inflammation may also increase photocarcinogenesis risk.
Nonetheless, many available products used in sun care focus on post-exposure effects,8 while agents to protect against or prevent UV skin damage are barely explored. Agents that protect against photoaging could be key to maintaining overall skin health and preventing UV-related skin disorders.
Figure 5. Co-culture model with human epidermal keratinocytes and HDFCourtesy of Nattaya Lourith
In the previously described study, a co-culture model incorporating human epidermal keratinocytes (HaCaT) and HDF was used to test the effects of the food phenolics against photoaging. The phenolics (150 μg/mL) were not only safe in the co-culture model, they also provided protection against UVA and UVB. Further, IL-6 and the chemokine IL-8 were suppressed following photodamage, similarly to the MMP-1 and MMP-9 results (see Figure 5). Again, caffeic acid was found to be the most potent, in alignment with the results of the HDF test.6
Discussion and Conclusion
Caffeic, sinapic and rosmarinic acids were evaluated elsewhere for their potential to efficiently modulate critical pathways of skin aging; i.e., senescent aging, photoaging and inflammatory aging. As this overview explains, such food phenolics demonstrated strong potential, underscoring the opportunity to upcycle effective skin care solutions sustainably from food by-products.
The global agro-industry generates millions of tons of food crops, some from organic farms that comply with controlled practices in agriculture and harvesting. Food crops are therefore available and ready to be diversified from their conventional consumption.
The transformation of these food phenolics into high-value cosmetic ingredients epitomizes a biocircular economy. Moreover, advanced green chemistry extraction technologies can ensure high-quality, standardized phenolic extracts are produced, valorizing excluded or leftover parts from food processing and giving the industry the confidence to formulate with these materials.
Finally, processing food phenolics adds value to the agricultural supply chain while aligning with the growing consumer demand for clean, sustainable and natural beauty products. From an industrial perspective, this also aligns with the principles of green chemistry, maximizing the incorporation of all materials from the feedstock into final products.
References
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