Isolation, structural characterization, and anticomplement activity of two glycoproteins derived from Commelina...

Commelina communis L., known as Commelinae Herba in traditional Chinese medicine, has been widely used to treat infections. Recent studies have shown that C. communis exhibited notable anticomplement activity and contained diverse compounds. However, limited investigations addressed the anticomplement glycoproteins from this plant. To bridge this knowledge gap, two macromolecules (CCW-4 and CCW-5) were isolated and characterized from C. communis. Composition analysis indicated that CCW-4 and CCW-5 were acidic glycoproteins featuring N-linked glycans. Significantly, CCW-5 exhibited potent anticomplement activity through the classical pathway, with a half hemolytic inhibition concentration (CH₅₀) value of 39.8 ± 2.9 μg/mL, markedly stronger than that of CCW-4 (407.1 ± 34.3 μg/mL). Intriguingly, the protein part of CCW-5 demonstrated even greater potency, achieving a CH₅₀ value of 7.5 ± 0.5 μg/mL. Surface plasmon resonance analysis further revealed that CCW-5 bound with C1q (KD = 0.29 μM) and C5 (KD = 0.42 μM) with approximately 8-fold and 16-fold greater affinity, respectively, than that of CCW-4 (KD = 2.36 μM for C1q and 6.6 μM for C5). These results demonstrated that anticomplement glycoproteins were significantly active constituents in the water extract of C. communis, potentially paving the way for the discovery of glycoprotein-based compounds to combat respiratory infections.