Medicinal Plants Against Herpes Simplex Virus (HSV) Type 2 Infections: Ethnopharmacology, Chemistry, and Clinical and Preclinical Studies

Herpes simplex viruses (HSV), long double-stranded DNA viruses, cause various types of infections in the human body. HSV-1 causes predominantly orofacial infection, whereas HSV-2 provokes principally genital infection. It is reported that when HSV-2 attacks neurons especially those of the eye and the brain, it causes herpes keratitis and herpes encephalitis respectively. HSV-2 is liable to cause various life-threatening diseases like Alzheimer’s disease, acquired immunodeficiency syndrome (AIDS), and encephalitis, and even death may occur. Moreover, the resistance of HSV-2 to the current available nucleoside derivative drugs such as acyclovir and valaciclovir originated the search for vital and useful therapies for the management of HSV-2 manifestation. The researchers are very much interested to naturally occurring substances to discover potential phytoconstituents or a mixture of phytoconstituents or a mixture of herbs with nucleotide analogs so that the expenditure, as well as the problems regarding resistance to drug and recurrence of infections, will be minimized. Various scientific evidences have proved that a lot of natural plant products are capable to prevent the infections caused by HSV-2. Several review papers reveal that compounds isolated from various plants, like phenolic acids, flavonoids, alkaloids, tannins, saponins, lignan terpenoids, essential oils, etc., exhibit anti-viral properties against HSV-2. The medicinal plants are indicated to be highly promising medicine against simplex herpes virus, the mechanism of which is either directly preventing life cycle such as adsorption, penetration, genetic material replication, and protein synthesis or indirectly improving the immunity of the human body. This chapter is focused on the study of the cell structure of herpes simplex virus type 2 and its replication inside the host cell, medicines derived from natural sources mainly from whole plants or plant parts, the chemistry of phytoconstituents, and preclinical and clinical trials of recently developed drugs with their future trends.