Nadezhda Markova1, Maya Margaritova Zaharieva2, Petia Genova-Kalоu3, Stefka Krumova3, Ivayla Dincheva4, Ilian Badjakov4, Lyudmila Dimitrova2, Venelin Enchev5 and Hristo Najdenski2
1 Institute of Organic Chemistry with Centre of Phytochemistry, Bulgarian Academy of Sciences, 1113 Sofia, Bulgaria
2 Department of Infectious Microbiology, The Stephan Angeloff Institute of Microbiology, Bulgarian Academy of Sciences, 1113 Sofia, Bulgaria
3 Department of Virology, National Centre of Infectious and Parasitic Diseases, 1233 Sofia, Bulgaria
4 Department of Agrobiotechnologies, Agrobioinstitute, Agricultural Academy, 1164 Sofia, Bulgaria
5 Institute of General and Inorganic Chemistry, Bulgarian Academy of Sciences, 1113 Sofia, Bulgaria
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
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 (MICFraction 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.