Viapiana A, Wesolowski M. The phenolic contents and antioxidant activities of infusions of Sambucus nigra L. Plant Foods Hum Nutr. 2017;72(1):82-87.

Elder (Sambucus nigra, Adoxaceae) berry juice and flowers are popular food additives. In folk medicine, the berries and flowers are used to prevent degenerative diseases, cancer, inflammation, cardiovascular disease, and diabetes. Both fruits and berries are known to contain various phenolic compounds (i.e., chlorogenic acid [CGA], gallic acid [GA], and rosmarinic acid) that have been reported to be potent antioxidants. Additionally, CGA has been demonstrated to have antioxidative, hepatoprotective, and hypoglycemic activities. GA may have benefits in Alzheimer's disease. Rosmarinic acid has been shown to have HIV-1 inhibitory activity, antitumor activity, and antihepatitis activity. The purpose of the in vitro study, summarized herein, was to analyze the antioxidant potential of teas prepared from a total of 24 dry commercial elderberry and elderflower products sold as loose or bagged materials.

Among the purchased samples, 11 whole dried elderberry and five crumbled dried elderflower products were originated in Poland. Serbia was the country of origin for eight other crumbled dried elderflower materials. Tea infusions were prepared as follows: 1 g plant material was infused with 200 mL boiling water for 15 min and then filtered. Total phenolic, phenolic acid, and flavonoid contents were quantified using the Folin-Ciocalteu method, the Arnov method from the Polish Pharmacopoeia, and the aluminum chloride method, respectively. The most abundant flavonols (quercetin, kaempferol, myricetin, and rutin) and phenolic acids (gallic, syringic, ferulic, caffeic, coumaric, and chlorogenic acids) were also quantified by high-performance liquid chromatography with ultraviolet detection (HPLC-UV). The global antioxidant activity of the prepared infusions was measured by two widely used assays. The first assay measures the radical scavenging properties of a sample through the reduction of the a 2,2-diphenyl-1-picrylhydrazyl (DPPH) reagent, and the second one measures the ferric reducing antioxidant power (FRAP).

The authors compared the HPLC-determined phenolic composition of loose versus bagged products and found that they differed in the levels of caffeic acid (P = 0.002) and p-coumaric acid (P = 0.01). The samples from Poland versus Serbia differed only in the level of myricetin (P = 0.02). The elderberry and elderflower products had different levels of quantified flavonols and phenolic acids. Both were found to contain more flavonols than phenolic acids (expressed in mg/g dry weight). The elderflower teas had the highest concentration of quercetin, while elderberry teas had the highest concentration of myricetin. As such, the elderberry infusions contained quercetin > rutin > kaempferol > myricetin > syringic acid > caffeic acid > GA > ferulic acid > p-coumaric acid > CGA. The elderflower infusions contained myricetin > quercetin > rutin > kaempferol > CGA > syringic acid > caffeic acid > GA > ferulic acid > p-coumaric acid. Moreover, the elderflower teas had significantly more total phenolic, total phenolic acid, and total flavonoid contents than the elderberry teas. Interestingly, elderflower teas also had higher DPPH and FRAP activities (= antioxidant activities) compared with elderberry teas. As a result of Pearson's correlation analysis, the authors found a high correlation (correlation r > 0.6) between the total phenolic content and the antioxidant activities measured for both the flower and berry teas, thereby suggesting that a high total phenolic content was associated with high antioxidant activities. A good correlation was also observed between the total flavonoid content and the antioxidant potential measured for the elderflower teas.

In comparison with previously published results, the authors observed that the antioxidant activity of elderflower tea was greater than published DPPH activity for strawberry (Fragaria spp., Rosaceae) fruit tea, raspberry (Rubus spp., Rosaceae) fruit tea, and blueberry (Vaccinium spp., Ericaceae) fruit tea but was similar to their published FRAP activities. However, the authors did not indicate whether these teas were prepared according to the same infusion method.

The authors conclude that elderflower/elderberry tea is a dietary source of natural antioxidants. Specifically, elderflower teas were found to have the highest total phenolic (including phenolic acids and flavonoids) content and the highest mean DPPH and FRAP antioxidant activities, as compared to the elderberry teas. The authors acknowledged that the efficient extraction of phenolic compounds, and thus, their overall antioxidant properties, can vary according to the extraction processes (e.g., extraction method, solvent type, temperature, drying) of the plant material but also the environmental stresses (e.g., storage, soil, agronomic practices, climate) related to their cultivation. The authors declare no conflict of interest.