BIOACTIVE POTENTIAL OF JERUSALEM ARTICHOKE (Helianthus tuberosus L.): PHENOLIC CONTENT AND ANTIOXIDANT ACTIVITY IN DIFFERENT PLANT FRACTIONS

Interest in plant-based raw materials has increased due to the growing demand for health-promoting foods and the potential utilization of lesser-known plants species, such as Helianthus tuberosus L. Phenolic compounds are recognized for their antioxidant activity and potential for cellular protection. Therefore, this study aimed to determine and compare the total phenolic content (TPC) and antioxidant activity of the ray florets, central disc, and rhizome of Helianthus tuberosus L. Samples collected in São Lourenço do Sul, RS, were analyzed at the Food Technology Laboratory (LTA) of FURG. The materials used included fresh ray florets (FRF), dried ray florets (DRF), fresh central disc (FCD), dried central disc (DCD), and fresh rhizome (FR); drying was performed in a forced-air circulation oven at 45 °C for 19 hours for the ray florets and 24 hours for the central disc. The TPC were extracted with methanol and quantified using the Folin-Ciocalteu method, with absorbances measured at 750 nm and results calculated using a gallic acid calibration curve. Antioxidant activity was determined using DPPH and ABTS+ radical scavenging assays, with Trolox as the standard. Results were expressed in µmol TE/g and percentage of maximum inhibition. Analyses were performed in triplicate, and data were subjected to ANOVA followed by Tukey's test (p<0.05). TPC varied among plant fractions and processing conditions: FRF: 1101.49 ± 219.50 µg GAE/g; DRF: 1453.48 ± 173.33 µg GAE/g; FCD: 1201.02 ± 34.92 µg GAE/g; DCD: 1743.17 ± 265.88 µg GAE/g; FR: 90.52 ± 16.39 µg GAE/g. The differences may be associated with the distribution of phenolic compounds among plant tissues; while the higher levels in dried samples may results from water removal and changes in the extractability of these compounds. Antioxidant activity varied according to the assay used. In the DPPH assay, DRF and FCD showed the highest values (0.192 ± 0.012 and 0.180 ± 0.003 µmol TE/g, respectively), with no significant difference between them (p>0.05). FRF showed an intermediate value (0.133 ± 0.020 µmol TE/g), while FR and DCD (0.006 ± <0.001 and 0.039 ± <0.001 µmol TE/g) showed the lowest values, differing significantly from each other (p<0.05). Maximum inhibition values were 87.20%, 81.52%, 60.33%, 29.02%, and 17.61%, respectively. In the ABTS+ assay, FR exhibited the highest activity (p<0.05) at 7.942 ± 0.343 µmol TE/g, whereas FRF, DRF, FCD and DCD showed 0.030 ± 0.001, 0.197 ± 0.002, 0.051 ± 0.005, and 0.142 ± 0.004 µmol TE/g, respectively, with no significant differences among them (p>0.05). The maximum inhibition values were 35.52%, 26.60%, 87.58%, 22.57%, and 62.66%, respectively. Difference between the methods may be attributed to the chemical characteristics and reaction kinetics of the radicals, as well as their differential reactivity toward the antioxidants present in the plant matrix.