**2. Results**

#### *2.1. Yield of Hesperidin Extracted from Humid Orange Peel—Green Method*

The obtained hesperidin was pale yellow amorphous powder (Supplementary Information Figure S1). The yield of HSD extracted in this manner was ~1.2% calculated per dry orange peel bagasse. The same method was repeated varying calcium(II) chloride solution concentrations—5% and 10%—but HSD yields were significantly lower when compared to one obtained with 7.5% calcium(II) chloride solution. In addition, the color of the solution with 7.5% calcium(II) chloride was much darker than obtained with the other two solutions (Figure S1, Supplementary Information). In the case of 5%, there are not enough calcium(II) ions to react the pectin and disrupt interaction of HSD with the macromolecule, and in the case of 10% of the solution, calcium(II) interactions with HSD are due to their ability to chelate metal ions.

#### *2.2. Spectral Data and Characterization of Obtained HSD*

The chemical structure and purity of the obtained HSD were analyzed applying High-field Nuclear Magnetic Resonance (NMR) (Supplementary Information Figures S2 and S3), Fourier Transform-Infrared (FT-IR) spectroscopy and Ultra High-Performance Liquid Chromatography (UPLC, Supplementary Information Figure S3) techniques. All HSD NMR peak assignments of proton and carbon signals were in accordance with the literature [32]. From the 1H NMR spectrum of the obtained HSD, typical flavanone structure signals could be assigned at δ 12.02 (1H, s, 5-OH) and δ 9.09 (1H), which originate from two hydroxyl groups attached to an aromatic ring, further δ 5.51 (1H, dd, *J* = 12.1, 3.3 Hz, H-2), from protons of the 1,3,4-trisubstitued ring at δ 6.91 (3H, m), protons of rhamnose and glucose at δ 4.98 (1H, d, *J* = 7.3 Hz) and 4.53 (H, m), one methoxy group peak at δ 3.80 (3H, s), and one methyl group peak at δ 1.09 (4H, d, *J* = 6.2 Hz). The acquired Heteronuclear Single Quantum Coherence (HSQC) spectra (Figure S2) and Heteronuclear Multiple Bond Coherence (HMBC) spectra (Figure S3) of the extracted HSD were used to confirm its structure. HSD was monitored by UV maximum at 284 nm, caused by the conjugation of the keto group and the other oxygen atoms with the aromatic ring systems. HSD purity was determined utilizing Ultra High-Performance Liquid chromatography (UHPLC) with the reverse stationary phase (C18, length 10 cm, 5 μm). HSD analytical standard (Sigma-Aldrich, 97% of purity) was used for calibration curve construction from the injection of aliquots of 1, 2, 4, 6, 8, and 10 μL of standard HSD solution in methanol (concentration 100 ppm). Calibration curves and the analysis of the sample from the extraction were performed in triplicate. A solution of 100 ppm of HSD in methanol (HPLC grade of purity) was analyzed in UHPLC as to obtain the area of the peak and to determine the relative concentration of HSD, comparing to the Sigma-Aldrich standard of HSD with grade purity > 97%. The peak with the retention time of 6.877 min was assigned to HSD (Figure S3) as the same procedure was done with the standard for HSD (>97%, Sigma-Aldrich). The determined purity was 97.2%, m/m, when compared to the Sigma-Aldrich analytical standard (> 97%). Therefore, the applied extraction process was adequate and a high HSD yield was achieved, while purity of the extracted HSD was high. It was observed that low impurities coming from naringin were present (Supplementary Information Figures S2–S4).
