To control agronomic N losses and reduce environmental pollution, biological nitrification inhibition (BNI) is a promising strategy. BNI is an ecological phenomenon by which certain plants release bioactive compounds that can suppress nitrifying soil microbes. Herein, we report on two hydrophobic BNI compounds released from maize root exudation (1 and 2), together with two BNI compounds inside maize roots (3 and 4). On the basis of a bioassay-guided fractionation method using a recombinant nitrifying bacterium Nitrosomonas europaea, 2,7-dimethoxy-1,4-naphthoquinone (1, ED₅₀ = 2 μM) was identified for the first time from dichloromethane (DCM) wash concentrate of maize root surface and named “zeanone.” The benzoxazinoid 2-hydroxy-4,7-dimethoxy-2H-1,4-benzoxazin-3(4H)-one (HDMBOA, 2, ED₅₀ = 13 μM) was isolated from DCM extract of maize roots, and two analogs of compound 2, 2-hydroxy-7-methoxy-2H-1,4-benzoxazin-3(4H)-one (HMBOA, 3, ED₅₀ = 91 μM) and HDMBOA-β-glucoside (4, ED₅₀ = 94 μM), were isolated from methanol extract of maize roots. Their chemical structures (1–4) were determined by extensive spectroscopic methods. The contributions of these four isolated BNI compounds (1–4) to the hydrophobic BNI activity in maize roots were 19%, 20%, 2%, and 4%, respectively. A possible biosynthetic pathway for zeanone (1) is proposed. These results provide insights into the strength of hydrophobic BNI activity released from maize root systems, the chemical identities of the isolated BNIs, and their relative contribution to the BNI activity from maize root systems.

为了控制农艺氮损失和减少环境污染，生物硝化抑制（BNI）是一种很有前景的策略。BNI 是一种生态现象，通过这种现象，某些植物会释放可以抑制硝化土壤微生物的生物活性化合物。在此，我们报告了玉米根系分泌物释放的两种疏水性 BNI 化合物（1和2），以及玉米根部内的两种 BNI 化合物（3和4）。基于使用重组硝化细菌Nitrosomonas europaea的生物测定引导分馏方法，2,7-二甲氧基-1,4-萘醌 ( 1 , ED ₅₀ = 2 μM) 首次从玉米根表面的二氯甲烷 (DCM) 洗涤浓缩物中鉴定出来，并命名为“玉米酮”。 从玉米根的 DCM 提取物中分离出苯并恶嗪类化合物2-羟基-4,7-二甲氧基-2 H -1,4-苯并恶嗪-3(4 H )-one (HDMBOA, 2 , ED ₅₀ = 13 μM)，以及两种化合物2 的类似物，2-羟基-7-甲氧基-2 H -1,4-苯并恶嗪-3(4 H )-one (HMBOA, 3 , ED ₅₀  = 91 μM) 和 HDMBOA-β-葡萄糖苷 ( 4 , ED ₅₀  = 94 μM)，从玉米根的甲醇提取物中分离。它们的化学结构 ( 1 – 4) 是通过广泛的光谱方法确定的。这四种分离BNI化合物（的贡献1 - 4），以在玉米根疏水BNI活性均19％，20％，2％，和4％之间。提出了玉米酮 ( 1 )可能的生物合成途径。这些结果提供了对从玉米根系释放的疏水 BNI 活性强度、分离的 BNI 的化学特性以及它们对来自玉米根系的 BNI 活性的相对贡献的见解。