Twenty-two herbal supplements are studied for their free radical scavenging activities and four toxic metals Al, Cd, Ni, and Pb contents. The methanol extract (5%) of the studied products scavenged 20.05%–89.11% 2,2-diphenyl- 1-picrylhydrazyl radical at 517 nm, whereas it scavenged 39.60%–99.48% 2,2′-azinobis(3-ethylbenzothiazoline-6- sulfonic acid) radical cation was scavenged at 734 nm. The polyphenol contents were also determined and contained about 0.20–2.84 mg quercetin equivalent polyphenol per g of powder content. All the products passed the weight variation limits of the United States Pharmacopeia 42-National Formulary-37 for dietary supplements. The samples were prepared by microwave digestion technique and analyzed using inductively coupled plasma atomic emission spectroscopy for toxic metal analysis. The calibration curves were achieved using 0.01–5 μg/ml of multimetal standard solution, and the recoveries of the studied metals were from 97.10% to 100.06%. The products contained variable amounts of nonessential toxic metals such as 1.4502–8.7932 μg Al, 0.1401–3.1681 μg Ni, 0.0016–0.1166 μg Cd, and 0.0301–0.6630 μg Pb. Based on the recommended daily doses of the studied products, the daily intake of Ni, monthly intake of Cd, and weekly intake of Al and Pb were within the WHO recommended limits; hence, all the studied products were safe to consume for the recommended period specified on the label.
Key words: Herbal supplements, DPPH●, ABTS●+, radical scavenging activity, ICP-AES, toxic metal analysis
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