Viruses are responsible for a variety of human pathogenesis. Owing to the enhancement of the world population, global travel, and rapid urbanization, and infectious outbreaks, a critical threat has been generated to public health, as preventive vaccines and antiviral therapy are not available. Herbal medicines and refined natural products have resources for the development of novel antiviral drugs. These natural agents have shed light on preventive vaccine development and antiviral therapies. This review intends to discuss the antiviral activities of plant extracts and some isolated plant natural products based on mainly preclinical (in vitro and in vivo) studies. Twenty medicinal herbs were selected for the discussion, and those are commonly recognized antiviral medicinal plants in Ayurveda (Zingiber officinale, Caesalpinia bonducella, Allium sativum, Glycyrrhiza glabra, Ferula assafoetida, Gymnema sylvestre, Gossypium herbaceum, Phyllanthus niruri, Trachyspermum ammi, Withania somnifera, Andrographis paniculata, Centella asiatica, Curcuma longa, Woodfordia fruticose, Phyllanthus emblica, Terminalia chebula, Tamarindus indica, Terminalia arjuna, Azadirachta indica, and Ficus religiosa). However, many viruses remain without successful immunization and only a few antiviral drugs have been approved for clinical use. Hence, the development of novel antiviral drugs is much significant and natural products are excellent sources for such drug developments. In this review, we summarize the antiviral actions of selected plant extracts and some isolated natural products of the medicinal herbs.

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Selected formula consisted of three ingredients including dried leaves of Azadirachta indica, dried seeds of Sesamum indicum and Bees' honey which is clinically use for open wounds. The current study was designed as a microbiological assay and the key objective was to evaluate the antibacterial efficacy of TNK against laboratory specimen of Staphylococcus aureus (ATCC25923). The Anti-Bacterial Sensitivity Test was conducted according to the Kirby Bauer method using Agar Well Diffusion method by comparing the effect of Amoxicillin as the positive controller and distilled water as the negative controller in triplicates. The testing drug was assessed as D1 and D2 in 1:2 concentration ratios respectively. Results of the study were obtained through the diameter measurement of inhibitory zone and assessed using one -sample Ttest. D1 depicted p value as 0.024 and Ttest was 4.44. D2 depicted p value as 0.100 and T-test was 1.89. Comparing to the positive control drug, the hypothesis was generated as H 0 : <=19 mm and H 1 : >19 mm. Referring to hypothesis, H 0 of D1 was rejected and H 0 of D2 was not rejected. The significant level was considered less than 5%. D2 concentration of TNK was significant against laboratory specimen of Staphylococcus aureus. The study suggests that the TNK is consisted with an extrinsic effective antibacterial application for infected wounds which were caused by Staphylococcus aureus. Further clinical study on human subjects will verify the efficacy of TNK in clinical manifestations.