Identification of Rhododendron mariae extraction as a New Attachment Inhibitor against Dengue Virus by Targeting the Envelope Protein Domain III

Chunyang Tian¹Yuanru Zheng¹Dongkai Tang¹Haiyan Tian²Lingzhu Shi¹Xuemei He¹Jianhai Yu¹Lijun Yan¹Huihui CAO¹Wei Zhao¹Jun Shan Liu¹Linzhong Yu¹Zibin Lu^1*

• ¹School of Biotechnology, Southern Medical University, Guangzhou, China
• ²Jinan University, Guangzhou, China

Dengue virus (DENV), a mosquito-borne flavivirus, causes over 390 million annual infections globally with no approved antivirals. Rhododendron mariae (RM), a traditional Chinese herb rich in flavonoids and triterpenoids, is used for respiratory disorders, but its antiviral potential is underexplored. This study evaluated the activity and mechanism of RM-1, an extraction from RM, against DENV. In vitro, plaque reduction assays in BHK-21 cells determined RM-1's EC50 against DENV-2. Its broad-spectrum activity against four DENV serotypes was tested in Vero and Huh7 cells. In vivo, DENV-infected suckling mice received RM-1 (10 mg/kg), with viral loads, histology, and survival monitored.Mechanistic studies included attachment assays and molecular docking.RM-1 potently inhibited DENV-2 (EC50=2.24 μg/mL) and all serotypes in a dose-dependent manner by blocking viral attachment. In infected mice, RM-1 reduced disease severity, tissue lesions, viral loads in serum/brain/spleen, and improved survival. It targeted DENV envelope protein domain III (ED III), critical for host attachment. This is the first report that RM-1 acts as a novel DENV attachment inhibitor via ED III targeting. It holds promise as an antidengue therapeutic, supporting traditional herbs as antiviral sources for flavivirus drug development.