The UV-Vis spectra of the extracts from the red dragon fruit peel using (a) distilled water, (b) ethanol, and (c) acetone as the maceration solvents.

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... peel extract in distilled water only gave strong absorbance in the UV region without obvious absorption in the visible region as shown in Figure 2(a). In contrast, the peel extract in ethanol (Figure 2(b)) showed strong absorption peaks at 263 and 346 nm with a background level of absorption in the visible region, which was in good agreement with its yellow color. ...

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... peel extract in distilled water only gave strong absorbance in the UV region without obvious absorption in the visible region as shown in Figure 2(a). In contrast, the peel extract in ethanol (Figure 2(b)) showed strong absorption peaks at 263 and 346 nm with a background level of absorption in the visible region, which was in good agreement with its yellow color. On the other hand, the peel extract in acetone ( Figure 2(c)) showed weak absorption peaks at 331, 452, and 480 nm. ...

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... contrast, the peel extract in ethanol (Figure 2(b)) showed strong absorption peaks at 263 and 346 nm with a background level of absorption in the visible region, which was in good agreement with its yellow color. On the other hand, the peel extract in acetone ( Figure 2(c)) showed weak absorption peaks at 331, 452, and 480 nm. ...

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... shown in Figure 4(a1), the first pair of excitation and emission wavelengths were 291 and 353 nm, respectively. Meanwhile, the second pair is shown in Figure 4(a2), where the excitation wavelengths were 326 and 378 nm and the emission wavelength was 437 nm. The ethanolic extract also gave two pairs of excitation and emission signals, but with different wavelengths. ...

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... absorption properties of the extracts represent the natural compounds successfully extracted in the respective solvents. As shown in Figure 2, different solvents gave different properties of absorption spectra, suggesting that different compounds were succesfully extracted when using different solvents. ...

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... on the absorption spectrum shown in Figure 2(a), there was no clear absorption peak in the visible region that could be observed when distilled water was used as the solvent. This could be due to the low amount of pigment in the peel of the red dragon fruit that could be extracted by the distilled water, and thus, no valid pigment identification could be made. ...

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... could be due to the low amount of pigment in the peel of the red dragon fruit that could be extracted by the distilled water, and thus, no valid pigment identification could be made. The ethanolic extract from the peel of the red dragon fruit gave strong absorption peaks at 263 and 346 nm as shown in Figure 2(b), which indicated the presence of polyphenol derivatives [22]. Meanwhile, the peel extract in acetone ( Figure 2(c)) showed absorption peaks at 331, 452, and 480 nm, which corresponded to the presence of carotenoid pigment content as reported by Britton et al. [23]. ...

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... ethanolic extract from the peel of the red dragon fruit gave strong absorption peaks at 263 and 346 nm as shown in Figure 2(b), which indicated the presence of polyphenol derivatives [22]. Meanwhile, the peel extract in acetone ( Figure 2(c)) showed absorption peaks at 331, 452, and 480 nm, which corresponded to the presence of carotenoid pigment content as reported by Britton et al. [23]. Based on these absorption properties, the detected compounds in the peel of the red dragon fruit were carotenoid and polyphenol derivatives. ...