Connor English

Andrew Muelleman

Catechin Content and Seed Plasticity of Cooked Cranberry Beans

Cocoa beans and green tea are two substances that contain high concentrations of catechin, a phytochemical. Catechins are a class of flavonoids believed to contain natural antioxidant properties. Its antioxidant ability can be attributed to the three-ring structure. Catechin’s tri-phenolic structure allows it to inhibit oxidation reactions that produce highly reaction free radicals in the system[1] (Scheme 1). Along with its antioxidant effects, catechins are also inhibitors of lipid oxidation. Lipid oxidation is a major cause of heightened LDL cholesterol. It is known that a high ratio of LDL:HDL cholesterol is inimical to the heart and body.[2] Thus, the consumption of antioxidants is essential, since free radicals are more abundant in the system than naturally occurring antioxidants.

Using UV-Visible spectroscopy, the oxidation of catechin was measured as a function of pH and time (Figure 1). In a deaerated environment, there is no oxygen to oxidize the catechin, and one maximum peak is displayed. Absorbance is clearly not a function of time. However, in an aerated environment, catechin is shown to be a function of pH and time. As time progressed, the presence of oxygen in water oxidizes the beta ring of catechin causing a red-shift in the absorption wavelength and increased maxima. The absorption of the catechin solution increases as the environment becomes increasingly alkaline. The oxidation of catechin is thus proved to be a function of pH and time.

Differential Scanning Calorimetry (DSC) is used to show the difference in heat required to increase a samples temperature. DSC is primarily used to determine thermal transitions of a compound. DSC was performed on two beans, the raw Red Rider (RRR) and the nondarkening (CNDR) cranberry beans (Figure 2).[3] The phenolic content of RRRbeans is six times that of CNDR, and is shown in Figure 2 to decrease the transition temperatures of the second endothermic event, the enthalpy of melting. The increased phenolic content caused the overall sample to change the transition temperature to decrease.

Notes on Computational Methods:

To formulate the graphics for Figures 1 and 2, WebPlotDigitizer[4] was used to digitize the line and find data points on the line. Before using the digitized data, excel sheets were organized with five Gaussian functions for each line as indicated in the assignment. Each Gaussian function was created with a center (λmax), a width (σ), and a height (h). Once the Gaussian primitives were set up, a normalization factor (n) can be obtained. We then calculated the sum of normalized functions (ftot) at each value in the selected range of wavelengths. Itwas found that a lower step size, or the distance between each data point collected from the digitization (Δx = 2 for Figure 1, Δx= 0.5 for Figure 2),is advantageous to obtain a best match. The values of ftot were compared to the digitized values at each point by taking the magnitude of the difference, and not just the difference. This is done to prevent the error minimizing by having two large opposite values. The magnitudes of the differences were summed to find a value D. The Solver module was then used to change the parameters of each of the five nested Gaussian functions to minimize D, the sum of error. The Solving method that was utilized was GRG Nonlinear, but it is not clear whether that is the absolute best method to use or if another would be better. This resulted in Gaussian plots thatconverged to the literature data quite well with optimized parameters for each of the 5 curves to minimize D.

References:

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Connor English

Andrew Muelleman

Scheme 1. Redox Chemistry of Catechin

Figure 1. UV/Vis spectra of the pH dependence of catechin. For pH= 7 (λmax, m [nm], hm, σm [nm], nm): 246.914, 0.331, 5.968, 0.058 (m = 1); 272.527, 0.472, 19.201, 0.021 (m = 2); 310.233, 0.242, 32.246, 0.012 (m= 3); 415.018, 0.401, 28.140, 0.014 (m = 4); 497.046, 0.135, 43.453, 0.009 (m = 5). For pH= 7 deareated: 250, 0.1, 10, 0.040 (m=1); 275, 0.4, 13.933, (m = 2). For pH= 8: 242.283, 0.868, 8.693, 0.0309 (m = 1); 284.228, 0.757, 64.675, 0.00617 (m = 2); 288.791, 0.104, 8.337, 0.0476 (m = 3); 409.901, 0.821, 28.353, 0.0141 (m = 4); 482.331, 0.161, 47.641, 0.00837 (m = 5). For pH= 9: 242.283, 1.059, 8.693, 0.0309 (m = 1); 284.228, 0.898, 64.675, 0.00617 (m = 2); 288.791, 0.203, 8.337, 0.0476 (m = 3); 409.901, 1.059, 28.353, 0.0141 (m = 4); 482.331, 0.221, 47.641, 0.00837 (m = 5). For pH = 10: 242.283, 1.361, 8.693, 0.0309 (m = 1); 284.228, 1.181, 64.675, 0.00617 (m = 2); 288.791, 0.136, 8.337, 0.0476 (m = 3); 409.901, 1.240, 28.353, 0.0141 (m = 4); 482.331, 0.254, 47.641, 0.00837 (m = 5). For pH= 12: 242.283, 1.699, 8.693, 0.0309 (m = 1); 284.228, 1.303, 64.675, 0.00617 (m = 2); 288.791, 0.185, 8.337, 0.0476 (m = 3); 409.901, 1.412, 28.353, 0.0141 (m = 4); 482.331, 0.27, 47.641, 0.00837 (m = 5).

Figure 2. Thermograms determined by differential scanning calorimetry (DSC). For N = RR(r) s = -0.0328, C = -21.298 (Tmax (ᵒC), 1 (ᵒC),h1, n1): 79.16, 6.800, -0.728, 0.0587 (m = 1); 97.75, 5.497, -0.473, 0.0726 (m = 2). For N = CND(r) s = -0.0297, C = -22.448 (Tmax (ᵒC), 1 (ᵒC),h1, n1): 79.70, 5.5, -0.757, 0.0725 (m = 1); 97.50, 3.0, -0.836, 0.133 (m = 2).

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([1]) Sarkar, D.; Das, S.; Pramanik, A. A solution spectroscopy study of tea polyphenol and cellulose: effect of surfactants. RSC Adv.2014, 4, 36196-36205.

([2]) Nagao, T.; Komine, Y.; Soga, S.; Meguro, S.; Hase, T.; Tanaka, Y.; Tokimitsu, I. Ingestion of a tea rich in catechins leads to a reduction in body fat and malondialdehyde-modified LDL in men. Am. J. Clin. Nutr. 2005, 81, 122–129.

([3])Chen, P. X.; Dupuis, J. H.; Marcone, M. F.; Pauls, P. K.; Liu, R.; Liu, Q.; Tang, Y.; Zhang, B.; Tsao, R. Physicochemical Properties and in Vitro Digestibility of CookedRegular and Nondarkening Cranberry Beans (Phaseolus vulgaris L.)and Their Effects on Bioaccessibility, Phenolic Composition, andAntioxidant Activity. J. Agric. Food Chem. 2015, 63, 10448-10458.

([4])Rohatgi, A. WebPlotDigitizer, 2015.