Figure 1: Antiglycation Activity of Sweet Potato Extracts.

Antiglycation activity was evaluated using the HSA–glucose model. Extracts were tested at up to three concentrations (0.1–10 mg/mL), and only values within the linear range of the AG calibration curve were used to calculate AG equivalents (μmol AG-eq/g dry weight). All data are reported on a dry-weight basis of the lyophilized material. Values are mean ± SD (n = 3). Two-way ANOVA with Bonferroni’s post hoc test was used for statistical analysis. * p < 0.05; ** p < 0.01 vs. H₂O within each part. Different letters within each solvent indicate significant differences among parts (p < 0.05). Abbreviations: EtOH, ethanol; MeOH, methanol; CM, chloroform:methanol (2:1, v/v).

Figure 2: Total Polyphenol Content of Sweet Potato Extracts

Total polyphenols were determined by the Folin–Ciocalteu method. Extracts were tested at up to three dilutions (0.1–10 mg/mL), and only values within the linear range of the GA calibration curve were used to calculate gallic acid equivalents (mg GA-eq/g dry weight). All data are reported on a dry-weight basis of the lyophilized material. Values are mean ± SD (n = 3). Two-way ANOVA with Bonferroni’s post hoc test was used for statistical analysis. * p < 0.05; ** p < 0.01 vs. H₂O within each part. Different letters within each solvent indicate significant differences among parts (p < 0.05). Abbreviations: EtOH, ethanol; MeOH, methanol; CM, chloroform:methanol (2:1, v/v).

Figure 3: Caffeic Acid (CA) Content of Sweet Potato Extracts

Caffeic acid was quantified by HPLC. All data are reported on a dry-weight basis of the lyophilized material. Values are mean ± SD (n = 3). Two-way ANOVA with Bonferroni’s post hoc test was used for statistical analysis. * p < 0.05; ** p < 0.01 vs. H₂O within each part. Different letters within each solvent indicate significant differences among parts (p < 0.05). Abbreviations: EtOH, ethanol; MeOH, methanol; CM, chloroform:methanol (2:1, v/v).

Figure 4: Caffeoylquinic Acid (CQA) Content of Sweet Potato Extracts

CQAs were quantified by HPLC: (A) 3-CQA (3-O-caffeoylquinic acid), (B) 4-CQA (4-O-caffeoylquinic acid), and (C) 5-CQA (5-O-caffeoylquinic acid). All data are reported on a dry-weight basis of the lyophilized material. Values are mean ± SD (n = 3). Two-way ANOVA with Bonferroni’s post hoc test was used for statistical analysis. * p < 0.05; ** p < 0.01 vs. H₂O within each part. Different letters within each solvent indicate significant differences among parts (p < 0.05). Abbreviations: EtOH, ethanol; MeOH, methanol; CM, chloroform:methanol (2:1, v/v).

Figure 5: Dicaffeoylquinic Acid (diCQA) Content of Sweet Potato Extracts

diCQAs were quantified by HPLC: (A) 3,4-diCQA (3,4-dicaffeoylquinic acid), (B) 3,5-diCQA (3,5-dicaffeoylquinic acid), and (C) 4,5-diCQA (4,5-dicaffeoylquinic acid). All data are reported on a dry-weight basis of the lyophilized material. Values are mean ± SD (n = 3). Two-way ANOVA with Bonferroni’s post hoc test was used for statistical analysis. * p < 0.05; ** p < 0.01 vs. H₂O within each part. Different letters within each solvent indicate significant differences among parts (p < 0.05). Abbreviations: EtOH, ethanol; MeOH, methanol; CM, chloroform:methanol (2:1, v/v).

Figure 6: Correlations between Polyphenols and Antiglycation Activity

Associations were evaluated using Spearman’s rank correlation (ρ). Plots compare antiglycation activity (AG equivalents) with total polyphenol content (TPC) and with individual phenolics: CA, 3-CQA, 4-CQA, 5-CQA, 3,4-diCQA, 3,5-diCQA, and 4,5-diCQA. Abbreviations: CA, caffeic acid; CQA, caffeoylquinic acid; diCQA, dicaffeoylquinic acid; TPC, total polyphenol content.

Supplemental Figure 1: HPLC Chromatograms of Phenolic Compounds in Sweet Potato Extracts.

(A) Leaf, 100% Methanol Extract; (B) Stem, 40% Ethanol Extract; (C) Root, 100% Methanol Extract; (D) Storage Root, 60% Ethanol Extract.