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Voltammetric determination of b-carotene in fruits and vegetables

b-Carotene is a red-orange, fat-soluble carotenoid pigment found in fruits, vegetables and green leafy plants. It is one of the most abundant carotenoids found in the human diet and exerts numerous roles in biological systems. One of its major functions in humans is provitamin A activity. In addition, the consumption of a diet rich in b-carotene has been associated with a reduced risk for development of numerous oxidative-stress related diseases, such as cancer, cardiovascular diseases and various age-related degenerative diseases. These protective and therapeutic effects of b-carotene are mainly attributed to its antioxidant properties, i.e. the ability to quench reactive oxygen species and prevent or decrease oxidative damage to biomolecules (DNA, lipids and proteins). Owing to the beneficial health effects of b-carotene, there is an interest in developing a simple, rapid and reliable method for its determination in foods. b-Carotene is electroactive and can be electrochemically oxidized due to the conjugated double bonds. Depending on the analyte concentration differential pulse voltammetric response of b-carotene on a glassy-carbon electrode in acetone / 0.1 M NaClO4 consists of one or two peaks. At concentrations lower than 3x10-5 mol/L one main peak P1 was obtained. By increasing the concentration of b-carotene a small peak P2 at more positive potential appears. The oxidation potential of P1 is shifted toward higher values with increasing of b-carotene concentration. The relationship between peak potentials P1 and the logarithm of b-carotene concentration is linear, with the slope of DEP1/Dlog c = 0.067 V/d.u. Quantitative analysis of foodstuff was performed under experimental conditions of differential pulse amplitude 50 mV, interval time 0.15 s, pulse time 0.05 s and step potential 2 mV. Under these conditions, linear responses for b-carotene were obtained for concentrations from 4 x 10-6 mol/L to 1.1 x 10- 4 mol/L, and calculated LOD and LOQ were 2.5 × 10−6 mol/L and 8.2 × 10−6 mol/L, respectively. The proposed method was applied for the determination of b-carotene in extracts of different fruits (grapefruit, mango) and vegetables (carrot, butternut, sweet potato, spinach, kale and broccoli). Our results demonstrate that differential pulse voltammetry enables fast and simple quantification of b- carotene in a broad range of natural products.

b-carotene ; fruits ; vegetables ; voltammetry

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