Hybrid natural products produced via mixed biosynthetic pathways are unique andoften surprise one with unexpected medicinal properties in addition to their fascinating structural complexity/diversity. In view of chemical structures, hybridization is a way of diversifying natural products usually through dimerization of two similar or dissimilar subcomponents through a C-C or N-C covalent linkage. Here, we report four structurally attractive diterpene-alkaloid conjugates polyalongarins A-D (1-4), clerodane-containing aporphine and proaporphine alkaloids, the first of its kind from the barks of Taiwanese Polyalthia longifolia (Sonn.) Thwaites var. pendula. Inaddition to conventional spectroscopic analysis, single crystal X-ray crystallography was employed tode termine the chemical structures and stereo-configurations of 1. Compounds 1-4 were subsequently subjected to in vitro antiviral examination against DENV2 by evaluating the expression level of theNS2B protein in DENV2-infected Huh-7 cells. These compounds display encouraging anti-DENV2activity with superb EC50 (2.8-6.4 uM) and CCso values (50.4-200 uM). The inhibitory mechanismof 1-4 on NS2B was further explored drawing on in-silico molecular docking analysis. Based on calculated binding affinities and predicted interactions between the functional groups of 1-4 and the allosteric-site residues of the DENV2 NS2B-NS3 protease, our analysis concludes that the clerodane-
aporphine/proaporphine-type hybrids are novel and effective DENV NS2B-NS3 protease inhibitors.
