Isolation and identification of compounds from Kalanchoe pinnata having human alphaherpesvirus and vaccinia virus antiviral activity.

Context: Kalanchoe pinnata (Lam.) Pers. (Crassulaceae) is a succulent plant that is known for its traditional antivirus and antibacterial usage.
Objective: This work examines two compounds identified from the K. pinnata plant for their antivirus activity against human alphaherpesvirus (HHV) 1 and 2 and vaccinia virus (VACV).
Materials and Methods: Compounds KPB-100 and KPB-200 were isolated using HPLC and were identified using NMR and MS. Both compounds were tested in plaque reduction assay of HHV-2 wild type (WT) and VACV. Both compounds were then tested in virus spread inhibition and virus yield reduction (VYR) assays of VACV. KPB-100 was further tested in viral cytopathic effect (CPE) inhibition assay of HHV-2 TK-mutant and VYR assay of HHV-1 WT.
Results: KPB-100 and KPB-200 inhibited HHV-2 at IC ₅₀ values of 2.5 and 2.9 μg/mL, respectively, and VACV at IC ₅₀ values of 3.1 and 7.4 μg/mL, respectively, in plaque reduction assays. In virus spread inhibition assay of VACV KPB-100 and KPB-200 yielded IC ₅₀ values of 1.63 and 13.2 μg/mL, respectively, and KPB-100 showed a nearly 2-log reduction in virus in VYR assay of VACV at 20 μg/mL. Finally, KPB-100 inhibited HHV-2 TK- at an IC ₅₀ value of 4.5 μg/mL in CPE inhibition assay and HHV-1 at an IC ₉₀ of 3.0 μg/mL in VYR assay.
Discussion and Conclusion: Both compounds are promising targets for synthetic optimization and in vivo study. KPB-100 in particular showed strong inhibition of all viruses tested.