Inhibitory effects of compounds isolated from Decne peel on particulate matter-induced pulmonary injury in mice.

Particulate matter 2.5 (PM), with an aerodynamic diameter of ≤2.5 μm, is the primary air pollutant that plays a key role associated with lung injury produced by loss of vascular barrier integrity. Decne (Chinese yam), a perennial plant belonging to Dioscoreaceae family, is widely cultivated in tropical and subtropical regions across Asia. Both aerial parts and root of are consumed for nutritional and medicinal purposes. The aim of this study was to (1) identify the bioactive compounds present in peel which may be responsible for inhibition of PM-induced pulmonary inflammation in mice and (2) examine mechanisms underlying the observed effects of these compounds on mouse lung microvascular endothelial cells. The measured parameters include permeability, leukocyte migration, proinflammatory protein activation, reactive oxygen species (ROS) generation, and histology. Two phenanthrene compounds, 2,7-dihydroxy-4,6-dimethoxyphenanthrene (1) and 6,7-dihydroxy-2,4-dimethoxyphenanthrene (2) were isolated from peels. Both these phenanthrene compounds exhibited significant scavenging activity against PM-induced ROS and inhibited ROS-induced activation of p38 mitogen-activated protein kinase. In addition, enhancement of Akt pathway, involved in the maintenance of endothelial integrity, was noted. These phenanthrene compounds also reduced vascular protein leakage, leukocyte infiltration, and proinflammatory cytokine release in the bronchoalveolar lavage fluid obtained from PM-induced lung tissues. Evidence thus indicates that phenanthrene compounds derived from may exhibit protective effects against PM-induced inflammatory lung injury and vascular hyperpermeability in mice.