Harnessing nature’s defenses: Stinging nettle and dead man’s fingers fungi emerge as skin protectors
17 Nov 2023 --- In exploring new natural actives for skin protection, Polish researchers have delved into the effects of Urtica dioica extract, commonly known as stinging nettle, under oxidative stress conditions. Simultaneously, Vietnamese scientists have explored using crude melanin extracted from the fungus Xylaria, or dead man’s fingers, in synthesizing silver nanoparticles, which have demonstrated potent antibacterial activity against skin-infecting bacteria.
The latter research paper uncovered that crude melanin found in the stromata of some Xylaria species — recognized for their multifaceted properties — are a key component in naturally synthesizing silver nanoparticles.
The study found these “significant amounts of melanins” show “strong antioxidant and anti-UV activities without toxicity toward human skin cells.”
Battling acne at the nanoscale
The study evaluated the antibacterial functions of melanin-mediated silver nanoparticles against skin-infecting bacteria, namely Staphylococcus aureus and Cutibacterium acnes. The results demonstrate significant potency against both bacteria.
The crude melanin was found to inhibit Cutibacterium acnes by 90% at 15.625 µg/mL and Staphylococcus aureus by 90% at 62.5 µg/mL.
The melanin-mediated silver nanoparticles displayed superior antibacterial activities compared to the positive control (erythromycin), with lower minimum inhibitory concentration, according to the researchers.
The crude melanin was found to inhibit Cutibacterium acnes by 90% at 15.625 µg/mL and Staphylococcus aureus by 90% at 62.5 µg/mL.The research methodology involved mixing crude melanin solution extracted from Xylaria stromata with 0.1 M silver nitrate and incubating the concoction at 100 °C for three hours. This resulted in spherical silver nanoparticles with an average size of 18.85 ± 3.75 nm, showcasing the feasibility of utilizing crude melanin for direct silver nanoparticle synthesis.
Implications for the skin care sector
The study’s findings open new possibilities to naturally synthesize silver nanoparticles for use in skin care in formulations targeting acne-causing bacteria, safely and efficiently.
However, further research is crucial to understand and mitigate impurities in the synthesized silver nanoparticles. Additionally, exploring toxicity levels on skin cells is essential for advancing toward practical applications, highlight the researchers.
Working with plants to biosynthesize valuable cosmetic actives is an expanding body of research. Earlier this month, for instance, a separate research study showed how encapsulating black pepper’s alkaloid, piperine, in polymeric nanoparticles can unlock its benefits for topical applications.
In other research, scientists have harnessed Dendrobium anosmum, a species of orchid, to naturally synthesize zinc oxide nanoparticles to combat acne and the untapped potential of hyaluronic acid-based nanogels.
Stinging out stress
In other research on nature-based skin care protection, Polish researchers have investigated the stinging nettle’s protective benefits on human skin fibroblasts under oxidative stress conditions.
The stinging nettle, a perennial flowering plant with distinctive stinging hairs, has been a staple in folk medicine across various cultures for centuries.
Rich in nutrients, including vitamins B6, B2, A and K, as well as minerals like magnesium and calcium, it has been traditionally used to address various ailments, from arthritis to allergies, highlight the authors.
Previous scientific studies have revealed the plant’s anti-inflammatory, antioxidant, antibacterial and analgesic activities.
Protective effects of stinging nettle
The study assessed nettle extract’s impact on human skin fibroblasts subjected to oxidative stress induced by hydrogen peroxide.
The researchers tested various solvents to prepare an extract rich in polyphenolic compounds with high antioxidant potential.
The study revealed that extraction with 80% ethanol, followed by drying and re-dissolving the extract in pure water, was more efficient than direct water extraction. This yielded an extract rich in polyphenolic compounds, with chlorogenic and caffeoylmalic acid as predominant compounds.
The extract exhibited antioxidant properties in various assays, did not exhibit cytotoxicity, and effectively reduced reactive oxygen species in hydrogen peroxide-stimulated cells.
Nettle plant with distinctive stinging hairs.
Phytochemical profiling
The researchers identified caffeic acid derivatives as being most predomiannt, with caffeoylmalic acid and chlorogenic acid being the most abundant in the plant extract.
They highlight that these stinging nettle compounds are well-known for their antioxidant potential and considered valuable in skin care.
Cell-based assays confirmed the extract’s safety, showing no adverse effects on cell metabolism or membrane integrity. Additionally, the extract proved to be protective against hydrogen peroxide-induced cytotoxicity.
The study positions Urtica dioica extract as a promising cosmetic additive for skin care products to combat oxidative stress and promote skin health. While various nettle-based products are already available in the market, the study suggests the development of efficient formulations, such as hydrogels, to enhance the delivery of phytochemicals into the skin.
Additionally, exploring other parts of the plant, like the flowers, could provide further insights into their biological activity and potential applications in skin care, suggest the authors.
In other recent botanical research, a study uncovered the potential of sourcing nanocellulose from cacao shells, a byproduct of the chocolate industry, for use in formulating stable water-based emulsions for cosmetics. Meanwhile, scientists have also tapped into ginger’s tyrosinase inhibition and radical scavenging powers for skin care.
By Venya Patel
