Researchers at Biolandes and Polyphénols Biotech have found antioxidant content in a poplar bud (Populus nigra). In "Phenolic Composition and Antioxidant Properties of Poplar Bud (Populus nigra) Extract: Individual Antioxidant Contribution of Phenolics and Transcriptional Effect on Skin Aging," an article that appeared in the American Chemical Society's Journal of Agricultural and Food Chemistry, the researchers suggest that an aqueous extract of P. nigra possesses antioxidant properties that could be utilized in nutraceuticals for an anti-aging skin benefit.
According to the research, which was led by Xavier Vitrac of Polyphénols Biotech, several species of Populus have been used in medicine, specifically for their anti-inflammatory properties. Among these species, it was found that the bud exudate of the black poplar (P. nigra) contained: the flavonoid aglycons; the flavanones pinecembrin and pinostrobin; flavonols galangin, quercetin and kaempferol; flavones chrysin and apigenin and esters of phenolic acids.
It has been identified that propolis contained antioxidant properties; however, while this antioxidant effect had been attributed, in part, to the poplar bud, its antioxidant properties had not been studied. The researchers, therefore, developed a P. nigra extract and tested its phenolic composition and antioxidant properties using ORAC and cellular antioxidant activity assays (CAA). Also, to test the extract's antioxidant effect in nutraceutical formulations, the transcriptional effect of the extract on skin aging was investigated on a replicative senescence model of normal human dermal fibroblasts (NHDF).
The group found that poplar bud extract had moderate antioxidant activity, with caffeic and p-coumaric acids being the major antioxidant contributors, with 24.94± 0.14 and 26.39±0.05% antioxidant contribution, respectively, as determined by ORAC assay. Although these two compounds represented nearly 50% of the antioxidant activity in the compound, they comprise only 2% of the compound.
The CAA assay showed that the extract presented strong cellular antioxidant properties, as it inhibits up to 50% of radical production at 200 μg/mL. Among the phenolic compounds, caffeic and ferulic acids presented the highest antioxidant activities with the inhibition of up to more than 60% of radical production at 200 μM, followed by pinocembring, which showed radical scavenging of up to 40%. Salicin, p-coumaric, isoferulic, di-O-methylcaffeic and cinnamic acids, as well as piinobanksin and pinobansin 5-methyl ether, presented lower antioxidant activities with inhibition of up to 30% of radical production at 200 μM. Poplar bud extract and almost all pure phenolic compounds in the assay exhibited a dose-dependent antioxidant activity, with caffeic acid showing the highest antioxidant activity.
In investigating the transcriptional effect of the extract on NHDF, the researchers found that it decreased the expression of catalase antioxidant enzyme gene, whose role, in combination with other enzymatic and nonenzymatic antioxidant systems, is to reduce reactive oxygen species and maintain the oxidative balance in cells. In addition, the extract upregulated catalase expression in normal cells (+130%).
The researchers concluded that the bud extract showed a potential benefit on skin aging. It noted that additional studies would be needed to determine the bioavailability of poplar bud extract's phenolic compounds, the biological properties of these compounds and their metabolites in vivo, and to demonstrate their protective and curative skin anti-aging effects.
Although the research focused on the anti-aging effects of the poplar bud extract in nutraceuticals, perhaps its anti-aging benefit can be utilized in future skin care formulations.
The authors acknowledged support from Conseil Regional d'Aquitaine and the Association Nationale de la Recherche Technique.