Screening of medicinal plants from El Salvador for anti-viral activity against Herpes simplex 1

Herpes simplex virus 1 is one of the most prevalent pathogens worldwide. Resistant strains to current anti-viral treatment have been reported, requiring the search for novel anti-virals. Using a qPCR method to assess anti-herpetic activity from natural products, we analyzed 72 plant extracts from El Salvador and identified eighteen methanolic extracts with anti-viral activity of ≥ 75%. Anti-herpetic activity has not been previously reported in fourteen of the plants (Euphorbia lancifolia, Piper tuberculatum, Cordia alliodora, Tecoma stans, Taraxacum officinale, Hamelia patens, Witheringia solanacea, Emilia fosbergii, Gnaphalium viscosum, Citrus aurantium, Ambrosia peruviana, Carica papaya, Solanum hazenii and Melothria pendula). Four extracts were from species with previously reported anti-herpetic activity (Plantago major, Psidium guajava, Sida acuta and Bursera simaruba). These extracts effective anti-viral concentrations (EC₅₀) were between 203 and 6.31 µg/mL, while the selectivity indexes (SI) were between 55.91 and 2.57. Euphorbia lancifolia showed the most effective anti-viral activity (EC₅₀ = 6.31 µg/mL, SI = 51.82).