Effects of Exogenous Selenium on Accumulations of Selenium, GABA and Antioxidant Activity of Chestnut During Germination

The objective of this study was to investigate the effect of exogenous selenium on selenium enrichment and antioxidant activity of germinated chestnuts. We treated ‘Zaofeng’ chestnuts with Na2SeO3 at concentration of 0, 20, 40, 60 and 80 mg/L, and analyzed, during germination, the level of total Se, SeCys2, MeSecys, SeIV, SeMet, SeVI, γ-aminobutyric acid (GABA), antioxidant enzyme (phenylalanine ammonialyase (PAL), glutathione peroxidase (GPX), superoxide dismutase (SOD) and catalase (CAT)) activity, non-enzymatic antioxidant substances (total polyphenols and flavonoids) content and antioxidant capacity (DPPH, ABTS). The results indicated that low concentrations of selenium (20–40 mg/L) significantly promoted the organic transformation of selenium, with a Se-enrichment rate over 74%. Antioxidant enzyme (PAL, SOD, CAT) activities and total phenol content were enhanced by 1.1 to 1.9-fold compared with the control, leading to a 12.2–29.2% improvement in antioxidant capacity (DPPH and ABTS). In contrast, the high concentration of selenium (80 mg/L) induced oxidative stress, inhibiting enzyme (PAL, SOD, CAT) activities (reduced by 14.1–20.5%) and decreasing antioxidant capacity (DPPH) by approximately 19.0%. During chestnut germination, selenite was absorbed by the embryo and subsequently transformed into organic Se in vivo, ultimately being stored mainly as SeCys2. The selenium enrichment rate decreased significantly with increasing Na2SeO3 treatment concentration: from 86.4% at 20 mg/L to 62.2% at 80 mg/L. Furthermore, treatment with 40 mg/L Na2SeO3 led to a significant increase in GABA content of germinated chestnuts, reaching 1.3 times that of the control group. Overall, germination with 20–40 mg/L Na2SeO3 is an effective condition for producing Se-enriched chestnut sprouts with enhanced GABA and antioxidant capacity, offering a potential functional food ingredient.