This study was aimed to determine the optimized extract for Pueraria lobata radix (PLR) and to evaluate the effects of PLR dietary supplementation in juvenile eels ( Anguilla japonica ). A 2 3 full factorial design used was to determine PLR, selecting extraction’s ethanol (EtOH) concentration, temperature, and time as factors. PLR’s extraction conditions were established as 100% EtOH at 25°C for 10 h, maximizing the yield of key bioactive isoflavonoids—puerarin and daidzein—while minimizing cytotoxicity. In a feeding trial with juvenile eels, dietary supplementation with PLR (1%–5%) enhanced mean growth performance, yet not statistically significant due to high individual variance. Interestingly, supplemented groups exhibited higher coefficients of variation in body size, reflecting increased interindividual growth variability. Despite these growth benefits, condition factor and hepatosomatic index (HIS) remained unaffected. Hematological parameters did not differ significantly between groups, although trends toward elevated alkaline phosphatase (ALP), total cholesterol (TCHO), HDL cholesterol (CHO), and triglyceride levels—and reduced glucose (GLU) concentrations—were observed in the PLR–fed eels. Nonspecific immune responses, including lysozyme and phagocytic activity, showed no significant differences. However, gene expression of hepatic antioxidant enzymes (Cu/Zn–SOD and Mn–SOD) were significantly upregulated, while key oxidative stress‐related genes (Keap1, Nrf2, and Gclc) and pro‐inflammatory markers (Hsp70, IFN‐α, and Myd88) were markedly downregulated. These results indicate that long‐term dietary PLR supplementation promotes growth in juvenile eels, likely by enhancing hepatic antioxidant defenses and suppressing inflammation.
Mendis et al. (Thu,) studied this question.