Cardol triene inhibits dengue infectivity by targeting kl loops and preventing envelope fusion

Dengue virus causes a global burden that specific chemotherapy has not been established. A previous report suggested that anacardic acid inhibited hepatitis C virus infection. Here, we explored structure activity relationship of anacardic acid, cardanol, and cardol homologues with anti-DENV cellular infectivities. Cardol triene showed the highest therapeutic index at 29.07 with the CC₅₀ and EC₅₀ of 207.30 ± 5.24 and 7.13 ± 0.72 µM, respectively. Moreover, we observed that the more unsaturated the hydrocarbon tail, the higher the CC₅₀s in all head groups. High CC₅₀s were also found in HepG-2, THP-1, and HEK-293 cell lines where cardol triene CC₅₀s were 140.27 ± 8.44, 129.77 ± 12.08, and 92.80 ± 3.93 µM, respectively. Cardol triene expressed pan-dengue inhibition with the EC₅₀s of 5.35 to 8.89 µM and kl loops of dengue envelope proteins were major targets. The strong binding energy at T48, E49, A50, P53, K128, V130, L135, M196, L198, Q200, W206, L207, I270, and L277 prevented cellular pH-dependent fusion. Zika virus kl loops were aligned in the closed position preventing cardol triene to bind and inhibit fusion and infectivity. This study showed for the first time that cardol triene had a potential for further development as anti-dengue inhibitors.