Pseuderanthemum carruthersii (Seem.) Guillaumin is a native tree in Vietnam. The water extract of the leaves from this tree gives a highly viscous product that has been used to heal wounds and treat inflammations. Our previous studies showed that the leaves of P. carruthersii have a high content of polysaccharides. In this study, the structure and influence of the neutral polysaccharide from Pseuderanthemum carruthersii (PCA1) on lipopolysaccharide (LPS)-stimulated RAW264.7 cells were investigated. The PCA1 isolated from P. carruthersii is a galactan-type polysaccharide, containing galactose (77.0%), 3-O-methyl galactose (20.0%), and arabinose (3.0%). Linkage analysis of PCA1 showed that both the 3-O-methyl galactose and galactose were 1,4-linked. The presence of 3-O-methyl galactose units as part of the polysaccharide is important and can be used as a chemotaxonomic marker. The molecular weight of the PCA1 was 170 kDa. A PCA1 concentration of 30–40 μg/mL strongly inhibited TNFα, IL-1β, and IL-6 inflammatory cytokine production, and reactive oxygen species (ROS) release. PCA1 had inhibitory activities on pro-inflammatory cytokine and ROS release in LPS-stimulated mouse macrophages in vitro through MAPK signaling.

Hygrophila ringens var. ringens is a medicinal plant of the Acanthaceae family. A soluble polysaccharide is extracted from H. ringens seeds using warm water, followed by deproteinization and purification using column chromatography. DL1 is characterized comprehensively using spectroscopic and chromatographic techniques and identified as a polymer containing xylose (Xyl; 78.5%) and 4‐O‐methyl‐d‐glucuronic acid (4‐O‐MeGlcA; 21.5 %). The most prominent glycosidic linkages detected are terminal‐xylose (T‐Xyl); 1,2,3,4‐Xylp; 1,2,4‐Xylp; and T‐4‐O‐MeGlcA. DL1 belongs to the xylan group and is a 4‐O‐methylglucuronoxylan. DL1 exhibits inhibition of bovine serum albumin denaturation with IC₅₀ values of 0.35 mg mL⁻¹ and a similar activity to diclofenac (non‐steroidal anti‐inflammatory drug). In a model of lipopolysaccharide‐stimulated macrophages, DL1 (20–40 µg mL⁻¹) strongly inhibits inflammatory cytokines and reactive oxygen species release without having significant macrophage cytotoxicity. The inhibitory effect of DL1 on inflammatory cytokines is mediated by the activation of mitogen‐activated protein kinases by inhibiting the phosphorylation of p38 and extracellular signal‐regulated kinase. These results highlight the potential of DL1 for treating inflammation through its cytokine‐suppressive activity.

Protease (PPL) was isolated from Pseuderanthemum latifolium B. Hansen and had a molecular mass of 70 kDa. The N-terminal sequence of PPL showed 70-80% similarity with of subtilisin-like serine proteases from plants, but it did not show any sequence homology with known plant proteases. Serine protease inhibitors (PMSF, DFP) effectively blocked about 90% of PPL activity. PPL was highly activity at the pH range from 6 to 9 and temperatures from 50 °C to 80 °C, with an optimum at pH 7.0 and temperatures 70 °C. PPL had stability in a variety of pH, temperature, surfactant and oxidizing agents. PPL with concentration of 2.5 µg completely hydrolyzed the Aα-chain of fibrinogen within 5 min and hydrolyzed the Bβ and the γ-chain after 10 h. Fibrin also was strong hydrolyzed by PPL with concentration of 0.3 µg. Thus, PPL is a unique serine protease, which it had strong fibrino(geno)lytic activities.