Phytochemical screening, anti-herpes simplex virus, and antibacterial activities of various fractions obtained from Graptopetalum paraguayense E. Walter extract

Nadezhda Markova; Maya M. Zaharieva; Petia Genova-Kalоu; Stefka Krumova; Ivayla Dincheva; Ilian Badjakov; Lyudmila Dimitrova; Venelin Enchev; Hristo Najdenski

Nadezhda Markova

, Maya M. Zaharieva

, Petia Genova-Kalоu

, Stefka Krumova

, Ivayla Dincheva

, Ilian Badjakov

, Lyudmila Dimitrova

, Venelin Enchev

, Hristo Najdenski

Abstract: Our previous studies have demonstrated that the methanol/water extract of Graptopetalum paraguayense E. Walter (GP) significantly inhibits herpes simplex virus type 1 (HSV-1) and exhibits moderate activity against Gram-positive bacteria. We conducted a metabolic profile of the plant, yielding three fractions (A-polar metabolites, B-fatty acids, sterols, tocopherols, and C-phenolic components), which were analyzed using GC-MS. This study tested these fractions for cytotoxic, antibacterial, and anti-HSV activities in vitro. Cytotoxicity was tested on the Vero cell line. The HSV strains tested included two wild-type (wt) strains sensitive to acyclovir (ACV), Victoria (HSV-1) and Bja (HSV-2), and two clinical isolates resistant to ACV (ACVR), DD (HSV-1) and PU (HSV-2). Antibacterial activity was tested against the following bacterial strains, as per ISO Standard 20776-1: Staphylococcus aureus ATCC 29213, Staphylococcus aureus ATCC 12600, Enterococcus faecalis ATCC 29212, Escherichia coli 25922, and Pseudomonas aeruginosa ATCC 27853. Fraction C from GP selectively inhibited HSV-1 Victoria replication at 0.01 mg/mL, offering 94.5% cell protection. Its antiviral effect against acyclovir-resistant HSV strains was low (25.5% cell protection), with IC50 values ranging from 0.01 to 0.1 mg/mL, but superior to that of ACV (10.8% cell protection). This fraction demonstrated activity against Staphylococcus aureus (MIC Fraction C = 0.625 mg/mL) and inhibited methicillin-resistant S. aureus biofilm formation by 50%-90%. Phenolic fraction was non-cytotoxic and caused no skin irritation in rabbits, making it a promising candidate for antiviral drug development against HSV-1 and topical treatment for Gram-positive bacterial infections.

Keywords: anti-HSV activity; antibacterial effect; cytotoxicity; effective concentration 50 (EC50); Graptopetalum paraguayense E. Walter; minimal inhibitory concentration (MIC)

Citation: Markova, N., Zaharieva, M. M., Genova-Kalоu, P., Krumova, S., Badjakov, I., Dimitrova, L., Enchev, V. & Najdenski, H. (2025). Phytochemical screening, anti-herpes simplex virus, and antibacterial activities of various fractions obtained from Graptopetalum paraguayense E. Walter extract. Bulg. J. Agric. Sci., 31(5), 997–1011

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Date published: 2025-10-28

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