DOI: 10.26650/istanbuljpharm.2026.1897699 ISSN: 2587-2087

HPLC Quantification of Protodioscin and in Vitro Antioxidant Capacity and Contamination Assessment in Tribulus terrestris L. Supplements

Tuğba İduğ, Işık Çelik, Ümit Can Erim
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Background and Aims: Tribulus terrestris L. (TT) is a widely used plant that is associated with benefits for athletic performance and sexual function. This study investigated the phytochemical composition, antioxidant capacity, and contamination assessment of TT food supplements commercially available in Türkiye.Methods: Seven different food supplements were randomly collected from online retailers, pharmacies, and herbal shops. Antioxidant activity, total phenolic content (TPC), and total phenolic acid content (TPAC) were evaluated in the hydroalcoholic extracts. Protodioscin concentration was measured by HPLC, and lead (Pb) and cadmium (Cd) contamination was assessed.Results: High-performance liquid chromatography (HPLC) analysis revealed considerable variation in protodioscin levels, ranging from 94.55 to 6827.12 μg/g extract. Antioxidant activity was assessed using multiple in vitro assays. The DPPH radical scavenging assay yielded IC50 values between 0.135 and 1.28 mg/mL, indicating variable antioxidant potential. TPC values ranged from 6.805 to 35.06 mg GAE/g extract, while TPAC ranged from 2.114 to 21.752 mg CE/g extract. In ferric reducing antioxidant power FRAP and CUPRAC assays, the results varied between 5.066–21.705 mg TE/g and 62.846–199.308 mg TE/g, respectively. Flame atomic absorption spectrometry (FAAS) analysis detected no Cd or Pb contamination in any sample.Conclusion: As far as we are aware, this is the first study on TT food supplements marketed in Türkiye and one of the few investigations worldwide. In conclusion, while no heavy metal toxicity was observed, the drastic variation in protodioscin levels poses a challenge for dosage consistency and expected efficacy.

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