Here, we compared the inhibitory efficacy of six iridoids constituting YPL-001 on mucus overexpression, and showed that verproside most effectively reduces COPD-related inflammation by suppressing the PKCδ activation and its downstream TNF/NF-κB and PMA/PKCδ/EGR-1 pathways. The gene discussed is PRKCD; the disease is chronic obstructive pulmonary disease.