From Traditional Plants to Functional Innovation: Development and Functional Characterization of a Nettle–Fenugreek–Lemon Peel Herbal Tea: Phytochemical, Antioxidant, Anti-Inflammatory, and Mineral Properties

Abstract

The development of plant-based functional formulations has gained increasing interest as an approach to valorizing natural resources and exploring their potential health-related applications. This study aimed to develop and characterize a herbal tea formulation combining Urtica dioica (nettle), Trigonella foenum-graecum (fenugreek), and lemon peel. These plant materials have been reported to contain several bioactive constituents, including phenolic acids and flavonoids in U. dioica, trigonelline, diosgenin, and steroidal saponins in T. foenum-graecum, as well as flavanones and other phenolic compounds in lemon peel.

The formulation was evaluated for its phytochemical, antioxidant, anti-inflammatory, and mineral characteristics. Total polyphenols, flavonoids, and tannins were quantified using spectrophotometric methods. Antioxidant activity was assessed using the 2,2-diphenyl-1-picrylhydrazyl (DPPH) radical-scavenging assay and reducing power, while anti-inflammatory activity was evaluated through inhibition of protein denaturation. Mineral analysis included the determination of iron, zinc, and magnesium, together with selected potentially toxic metals.

The formulation showed total polyphenol, flavonoid, and tannin contents of 96.5 ± 2.1 mg GAE/g, 45.8 ± 1.6 mg QE/g, and 32.4 ± 1.2 mg CE/g, respectively. It exhibited substantial antioxidant activity, with 81.4% DPPH radical-scavenging activity and an IC₅₀ value of 245.7 µg/mL, together with a reducing power of 1.92 ± 0.08 mmol Fe²⁺/g. The formulation also demonstrated anti-inflammatory activity, reaching 72.3% inhibition of protein denaturation at the highest tested concentration (p < 0.01). Mineral analysis revealed iron, zinc, and magnesium concentrations of 8.72 ± 0.14 mg/L, 3.45 ± 0.10 mg/L, and 12.9 ± 0.18 mg/L, respectively. The levels of the investigated potentially toxic metals, including lead, cadmium, and aluminum, remained within the safety limits considered in this study.

Overall, the developed herbal tea exhibited a phytochemically rich composition, marked antioxidant and in vitro anti-inflammatory activities, and a favorable mineral profile. However, individual phytochemical constituents were not experimentally identified in the present study. Further investigations using chromatographic techniques such as HPLC or LC-MS are therefore required to identify and quantify the specific bioactive compounds present in the formulation and to further evaluate their bioavailability, safety, and biological effects.