“Although the antioxidant potential of Urtica species is well known, the protective effects of U. thunbergiana against UVB-irradiated photoaging have not been explored,” the researchers wrote in their study, published in the Journal of Functional Foods.
According to them, the young leaves of U. thunbergiana, a species of the stinging nettle genus, are a common ingredient in traditional Chinese medicine. It also has culinary uses, appearing in soups and stews.
Its close relative, U. dioica, has a lot of literature backing it, from its benefits in improving muscles and joints to eczema to arthritis, because of its anti-inflammatory and anti-cancer activities. Though U. thunbergiana as a plant has been rarely studied, one of its components, chlorogenic acid, has some literature backing its dermatological effects.
While part of the study focused on discovering U. thunbergiana’s anti-photoaging effects and mechanism by examining collagen synthesis human skin cells, a significant portion of the study looked at the anti-oxidant and protective effects of ingesting the plant’s extract.
To do this, the researchers examined ultraviolet-B induced hairless mice. The sample used was 100 g of U. thunbergiana, powdered and extracted three times in 1 liter of 50% ethanol. Extracts were then combined, filtered, and concentrated by vacuum evaporation.
Twenty-four hairless mice were divided into four groups with six mice per cage: One cage of mice was fed normal diet and kept out of ultraviolet B irradiation. The following groups (16 mice) all were irradiated with ultraviolet B lights three times a week for nine weeks: A normal diet group; a group supplemented with 0.1% U. thunbergiana; and the final group supplemented with 1% U. thunbergiana.
Analysis: Botanical extract increased hydration, decreased erythema
Physiological changes to the mice’s skin was measured at the end of 10 weeks. Ultraviolet B-epxosed skin experienced decreased skin hydration and increased skin reddening (erythema) compared to the non-exposed skin. However, the tendency was reversed in groups supplemented with the botanical extract.
“Mouse skin treated with UT had better skin hydration, moisture levels, and a more youthful appearance than UVB control group skin,” the researchers wrote. “Compared with the [ultraviolet B-exposed, non-supplemented] control group, the groups treated with [U. thunbergiana] at two concentrations had significantly increased skin hydration by 142% and 172%, respectively.”
Additionally, the researchers found that in ultraviolet B-exposed skin, collagen fibers were irregular and disorganized; however, in the supplemented groups, their density was increased. The effects of the botanical extract were due to the presence of two active compounds, caffeic acid and chlorogenic acid, the researchers said.
There is promise for the plant’s extract to be used in beauty-from-within dietary supplements or functional foods, but more research is required to “determine if U. thunbergiana can also protect against ultraviolet B-induced skin photoaging in artificial human skin models and clinical trials.”
Source: Journal of Functional Foods
Published online ahead of print, http://dx.doi.org/10.1016/j.jff.2017.07.004
"Urtica thunbergiana prevents UVB-induced premature skin aging by regulating the transcription factor NFATc1: An in vitro and in vivo study"
Authors: Eunson Hwang, et al.