Lectins are carbohydrate-binding proteins with several bioactivities, including antimicrobial properties. Portulaca elatior is a species found at Brazilian Caatinga and data on the biochemical composition of this plant are scarce. The present work describes the purification of P. elatior leaf lectin (PeLL) as well as the assessment of its antimicrobial activity and toxicity. PeLL, isolated by chromatography on a chitin column, had native liquid charge and subunit composition evaluated by electrophoresis. Hemagglutinating activity (HA) of PeLL was determined in the presence of carbohydrates or divalent cations, as well as after heating and incubation at different pH values. Changes in the lectin conformation were monitored by evaluating intrinsic tryptophan fluorescence and using the extrinsic probe bis-ANS. Antimicrobial activity was evaluated against Pectobacterium strains and Candida species. The minimal inhibitory (MIC), bactericidal (MBC), and fungicidal (MFC) concentrations were determined. Finally, PeLL was evaluated for in vitro hemolytic activity in human erythrocytes and in vivo acute toxicity in mice (5 and 10 mg/kg b.w. per os). PeLL (pI 5.4; 20 kDa) had its HA was inhibited by mannose, galactose, Ca²⁺, Mg²⁺, and Mn²⁺. PeLL HA was resistant to heating at 100 °C, although conformational changes were detected. PeLL was more active in the acidic pH range, in which no conformational changes were observed. The lectin presented MIC and MBC of 0.185 and 0.74 μg/mL for all Pectobacterium strains, respectively; MIC of 1.48 μg/mL for C. albicans, C. tropicalis, and C. krusei; MIC and MFC of 0.74 and 2.96 μg/mL for C. parapsilosis. No hemolytic activity or signs of acute toxicity were observed in the mice. In conclusion, a new, low-toxic, and thermostable lectin was isolated from P. elatior leaves, being the first plant compound to show antibacterial activity against Pectobacterium.

凝集素是碳水化合物结合蛋白，具有多种生物活性，包括抗菌特性。Portulaca elatior是一种在巴西卡廷加发现的物种，关于这种植物的生化成分的数据很少。目前的工作描述了P. elatior的纯化叶凝集素 (PeLL) 及其抗菌活性和毒性的评估。PeLL 通过几丁质柱色谱法分离，具有通过电泳评估的天然液体电荷和亚基组成。PeLL 的血凝活性 (HA) 是在存在碳水化合物或二价阳离子的情况下以及在不同 pH 值下加热和孵育后测定的。通过评估内在色氨酸荧光和使用外在探针 bis-ANS 监测凝集素构象的变化。评估了针对Pectobacterium菌株和Candida物种的抗菌活性。确定了最小抑制 (MIC)、杀菌 (MBC) 和杀真菌 (MFC) 浓度。最后，评估了 PeLL 在人红细胞中的体外溶血活性和在小鼠体内的急性毒性（5 和 10 毫克/千克体重，口服）。PeLL (pI 5.4; 20 kDa) 的 HA 被甘露糖、半乳糖、Ca ²⁺、Mg ²⁺和 Mn ²⁺抑制。PeLL HA 耐 100 °C 的加热，但检测到构象变化。PeLL 在酸性 pH 范围内更活跃，其中未观察到构象变化。凝集素对所有Pectobacterium菌株的 MIC 和 MBC 分别为 0.185 和 0.74 μg/mL；白色念珠菌的 MIC 为 1.48 μg/mL ，C. tropicalis和C. krusei；C. parapsilosis的 MIC 和 MFC 分别为 0.74 和 2.96 μg/mL 。在小鼠中未观察到溶血活性或急性毒性迹象。总之，从P. elatior叶中分离出一种新的、低毒且耐热的凝集素，它是第一种对Pectobacterium显示出抗菌活性的植物化合物。