Fenugreek (Trigonella foenum-graecum L.) seeds are rich in polyphenols and flavonoids, which are compounds known for their antioxidant and enzyme-inhibitory activities and relevant to metabolic health. This study evaluated the effects of soaking and roasting, followed by simulated gastrointestinal digestion, on the bioactive profiles of fenugreek seeds.
Seeds were divided into two groups: raw (R) and soaked-roasted (SR) seeds. Each group was subjected to one of three treatments: no digestion (control), gastric digestion, or complete digestion (gastric plus intestinal phases). Total polyphenol and flavonoid contents were measured, alongside antioxidant capacity via FRAP and ORAC assays, and inhibitory activity was assessed against pancreatic lipase and α-amylase enzymes. Flavonoid levels remained stable throughout processing and digestion, whereas total polyphenols significantly increased during digestion, especially in the intestinal phase, reaching up to 17.86 mg GAE/g. Antioxidant activity showed differing trends: raw seeds had higher FRAP values (8.86 mg Fe²⁺/g), while processed seeds exhibited greater ORAC values (143.96 vs. 117.65 µmol TE/g). Simulated digestion enhanced antioxidant capacity in both groups, peaking after intestinal digestion, with a strong positive correlation between total polyphenols and ORAC. Thermal processing greatly reduced pancreatic lipase inhibition from 82.64% to 7.98%, although gastric digestion partially restored activity in processed seeds (51.01%). No lipase inhibition was detected after intestinal digestion. α-Amylase inhibition was only observed after intestinal digestion, with raw extracts showing higher inhibition (73.17%) than processed extracts (25.05%), indicating heat sensitivity of the bioactive compounds.
These results highlight that gastrointestinal digestion, particularly the intestinal phase, enhances polyphenol bioaccessibility and antioxidant potential, while enzyme inhibitory effects are more vulnerable to thermal processing and digestion. This provides useful insights into designing fenugreek-based functional supplements for metabolic health.
