Determination of Caffeine and Hydrogen Peroxide Antioxidant Activity of Raw and Roasted Coffee Beans Around Habru Woreda, Ethiopia Using UV-Vis Spectroscopy

Figures & data

Figure 1 Map of the study area.

Figure 2 Maximum wavelength (λ_max) of caffeine in distilled water with the UV-Vis spectroscopic method.

Figure 3 Maximum wavelength (λ_max) of caffeine in dichloromethane with the UV-Vis spectroscopic method.

Figure 4 Calibration curve of standard caffeine solution in distilled water.

Table 1 Caffeine Content in the Coffee Samples with Aqueous Phase Extraction

Sample Type	Sample Name	Caffeine Content±SD(ppm)
Bohoro coffee	Raw coffee	190.82±0.45
	Roasted coffee	160.05±0.38
Wurgisa coffee	Raw coffee	185.38±0.51
	Roasted coffee	134.65±0.29
Girana coffee	Raw coffee	176.95±0.46
	Roasted coffee	125.51±1.50

Note: Mean ± standard deviation (n=3).

Figure 5 Calibration curve of standard caffeine solution in dichloromethane.

Table 2 Caffeine Content in the Coffee Samples with Dichloromethane Extraction

Sample Type	Sample Name	Caffeine Content±SD(ppm)
Bohoro coffee	Raw coffee	198.00±2.09
	Roasted coffee	184.08±3.05
Wurgisa coffee	Raw coffee	145.94±0.79
	Roasted coffee	181.64±0.77
Girana coffee	Raw coffee	186.42±2.38
	Roasted coffee	177.11±3.59

Note: Mean ± standard deviation (n=3).

Figure 6 Comparison of the caffeine value in roasted coffee beans in the three sampling types.

Figure 7 Comparison of the amount of caffeine in raw coffee beans in the three sampling types.

Table 3 Mean Percentage of Hydrogen Peroxide Scavenging Activity of an Aqueous Phase Extraction of Coffee Bean Samples, by Sampling Site, and Ascorbic Acid

Concentration	% H2O2 Scavenging Activity (mean±SD)
	Bo Raw	Bo Roasted	Wu Raw	Wu Roasted	Gi Raw	Gi Roasted	Ref. (Assc)
20	39.90±1.35	45.50±1.12	39.00±1.3	51.39±0.92	38.8±1.38	47.8±0.60	52.82±1.25
40	56.41±0.33	68.76±0.53	64.40±0.86	72.05±0.71	65.26±0.89	65.83±0.65	65.00±0.55
60	66.61±0.47	71.48±0.54	68.50±0.63	75.77±0.45	70.34±0.54	71.23±1.0	68.23±0.36
80	71.58±1.02	76.30±0.48	75.02±0.55	78.43±0.38	75.81±0.34	75.52±0.47	75.43±0.48
100	75.29±0.87	79.72±0.47	77.87±0.37	83.38±0.85	78.00±0.43	79.81±0.32	83.32±0.30

Notes: Mean ± standard deviation (n=3)..

Abbreviations: Bo, Bohoro; Wu, Wurgisa; Gi, Girana coffee beans; Ref. (Assc), reference (ascorbic acid).

Table 4 Calibration Equations, Pearson Correlations, and IC₅₀ Values of an Aqueous Phase Extraction of the Coffee Samples, by Sampling Site

	Bo Raw	Bo Roasted	Wu Raw	Wu Roasted	Gi Raw	Gi Roasted	Ref. (Assc)
Regression equation with respective R^2	y=0.4298x + 36.173 R^2=0.9128	y=0.3799x + 45.558 R^2=0.796	y=0.4418x +38.45 R^2=0.8178	y=0.3518x +51.096 R^2=0.8121	y=0.4448x +38.957 R^2=0.7921	y=0.3686x +45.925 R^2=0.8774	y=0.3572x +47.531 R^2=0.9723
IC50	32.17	11.69	26.14	3.12	24.83	11.06	6.91

Abbreviations: Bo, Bohoro; Wu, Wurgisa; Gi, Girana coffee beans; Ref. (Assc), reference (ascorbic acid); y, percentage of hydrogen peroxide scavenging activity; x, concentration (ppm).

Figure 8 Comparison of the hydrogen peroxide scavenging activity of the coffee sample and ascorbic acid.