Pelargonium sidoides Root Extract: Simultaneous HPLC Separation, Determination, and Validation of Selected Biomolecules and Evaluation of SARS-CoV-2 Inhibitory Activity

This study aimed to establish a validated HPLC-UV analytical method for the determination of gallic acid, catechin, scopoletin, and umckalin in phytoformulations containing P. sidoides. Also, to assess the anti-SARS-CoV-2 effect of P. sidoides and these biomolecules in vitro. An HPLC-UV method was developed and verified by testing the commercial forms, Kalobin(®) and Umca(®). It revealed low detectable scopoletin and high umckalin levels. Pelargonium sidoides exhibited a significant reduction of SARS-CoV-2-induced cytopathic effect in Vero E6 cells (IC(50) 13.79 μg/mL and selectivity index, SI 6.3), whereas scopoletin showed a remarkable anti-SARS-CoV-2 activity with better selectivity (IC(50) 17.79 μg/mL and SI 14.22). An in-silico prediction of the drugability indicated that the studied biomolecules are under the acceptable norms of Lipinski’s rule, water-soluble, and showed high GIT absorption and bioavailability. Docking study towards the essential molecular targets for viral replication and entry of SARS-CoV-2 indicated good binding affinity of scopoletin (−6.4 Kcal/mol) towards the interface region between the SARS-CoV-2 spike protein RBD and the ACE2 surface receptor indicating the probability of interference with the viral entry to the human cells and showed H-bonding with His-41 in the active site of the main protease which may explain its high antiviral activity.