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Metabolites from South African Medicinal Plants as Dual-Function Inhibitors of the SARS-CoV-2 Papain-like Protease (PLpro)

Makhafola MA, Naidoo CM, Obi CL, Iweriebor BC, Olaokun OO, Prinsloo E, Kikuchi H, Zubair MS et al.

Life (Basel, Switzerland), 2026

Abstract

The SARS-CoV-2 papain-like protease (PLpro) is an essential viral enzyme that promotes viral polyprotein processing while simultaneously suppressing the host innate immune response, which makes it a primary target for developing antiviral drugs. The present study employs a comprehensive approach integrating untargeted metabolomic profiling, in silico molecular docking and dynamics simulations, Molecular Mechanics Generalized Born Surface Area (MM-GBSA) energetic assessments, and biochemical enzyme assays. This integrated method aims to discover natural PLpro inhibitors from two ethnomedicinal plants, Lippia javanica and Acorus calamus, which have long been utilized in African traditional medicine to treat respiratory diseases. Comprehensive metabolite profiling using untargeted Ultra-Performance Liquid Chromatography-Tandem Mass Spectrometry (UPLC-MS/MS) and Global Natural Products Social (GNPS) molecular networking revealed flavonoid glucuronides and phenylpropanoid derivatives as the major constituents in both plant species. In situ histochemical staining further offered spatial validation of phenolic- and lignin-associated tissues, supporting the phenolic-dominated molecular families detected by GNPS molecular networking. In silico evaluation of six selected compounds demonstrated spontaneous and thermodynamically favorable binding to PLpro, with ΔG_bind values ranging from -5.63 to -6.43 kcal/mol. Catechin-7-glucoside emerged as the lead compound, establishing multiple…

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