An optimized Maclura tricuspidata fruit extract enhances growth in juvenile Japanese eel (Anguilla japonica)

다국어 초록 (Multilingual Abstract)

There is growing interest in natural products as functional feed additives in Japanese eel (Anguilla japonica) aquaculture. This study evaluated an optimized extract of Maclura tricuspidata fruit (MTF- OE) as a dietary supplement for juvenile Japanese eels. Extraction conditions were optimized using a Box–Behnken design (BBD), with ethanol concentration, temperature, and extraction time as variables, and extraction yield, cytotoxicity, and major isoflavonoid yields as response parameters. The optimized extract was obtained using 50% ethanol at 40 °C for 5 h, producing high yield, low cytotoxicity, and elevated levels of 6,8-diprenylgenistein and gancaonin A. Dietary MTF-OEs at inclusion levels of 0.5% (MTF0.5), 1% (MTF1), and 2% (MTF2) were evaluated in juvenile eels during an eight-week feeding trial. Compared with the control diet, MTF1 significantly increased the final weight, weight gain and specific growth rate (P < 0.05). MTF-OE inclusion increased whole-body moisture and crude protein contents (P < 0.05), whereas reduced crude lipid content (P < 0.05). PUFA levels were numerically higher in the MTF0.5 and MTF1 groups. Lysozyme activity tended to increase in MTF1, whereas MPO activity was significantly reduced (P < 0.05). AST decreased only in MTF2, while ALT did not differ among groups. Histological examination revealed no apparent tissue alterations in MTF0.5 and MTF1, but inflammatory cell infiltration was observed in the liver and heart of MTF2. Overall, these results suggest that 1% MTF-OE has potential as a functional feed additive that may contribute to improved growth and physiological status in juvenile Japanese eels.