# Halophytes as Medicinal Plants against Human Infectious Diseases
## 3 Halophytes as a Source of Antimicrobial Compounds
### Antiviral Effects  
Viral diseases represent major threats to human health and a global challenge in terms of disease prevention and treatment [69]. They are caused by a large diversity of agents that also display a high rate of mutation and are easily spread by water, air, inert materials and person-to-person contacts, and therefore, are prone to pandemics in a world where people and products rapidly circulate between continents [68].  
Viral diseases can be treated with antiviral drugs. However, because of the intimate relationship between the virus and the host cells, the design of antiviral medicines that block the replication of the virus without causing unacceptable damage in the host represents a significant constraint in the progress of antiviral chemotherapy [70]. Moreover, vaccines and antiviral drugs are neither affordable nor readily accessible for general use in many developing countries. These circumstances lead to regaining interest in medicinal haplotypes as sources of antiviral compounds.  
Although in vitro tests are, in most cases, conducted with extracts containing mixtures of compounds and it is not possible to associate antiviral effects with specific bioactive molecules, there are now several halophytic plants for which antiviral effects have been demonstrated (Table 2). An extensive study of the antiviral potential of water:ethanol extracts of different plant parts of several halophyte species allowed the detection of anti-hepatitis B virus (HBV) activity in _Acanthus_ licifolius L., _Aegiceras corniculatum_ ([PERSON]) [PERSON], _Avicennia marina_ ([PERSON].) [PERSON], _Bruguiera cylindrica L., Ceriops decandra_ (Griff.) [PERSON], _Rhizophora apiculata_ [PERSON], _R. lamarckii_ [PERSON], _R. mucronata_ [PERSON], _Salicornia brachiata_ [PERSON] & [PERSON] and _Sesuvium portulacastrum_ [PERSON] and anti-human immunodeficiency virus (HIV) activity in _Aegiceras corniculatum_, _Ceriops decandra, Exococaria agallocha L., _Rhizophora apiculata_, _R. lamarckii_ and _R. mucronata_[71]. A leaf extract of _Sueda maritima_ Torr. containing polyphenols, flavonoids and tannins caused the inhibition of the HBV reverse transcriptase [72]. Extracts of _Limonium densiforum_ (Guss.) Kuntze shoots, also rich in phenolic compounds, caused direct inhibition of herpes simplex virus type 1 (HSV-1) [73], and ferulic acid and caffeic acids extracted from _Plantago major_ L. exhibited activity against herpes simplex virus 2 (HSV-2) [12; 27]. Extracts of _P. major_ also demonstrated activity against adenoviruses (ADV-3, ADV-8, ADV-11), and among the classes of bioactive compounds identified, caffeic acid was associated with the strongest antiviral activity [74]. Activity against influenza A viruses (H1N1 strain) was also detected in _L. densiforum_ extracts [55]. Extracts of halophytes have also demonstrated activity against the Newcastle disease virus (NDV), vaccinia virus (VV), encephalomyelitis virus (EMCV) and Semliki Forest virus (SFV) [71].  
\begin{table}
\begin{tabular}{c c} \hline \hline
**Virus** & **Plants Species** & **Reference** \\ \hline \hline \multicolumn{3}{c}{_Acanthus licifolius_} \\ \multicolumn{3}{c}{_Aegiceras corniculatum_} \\ Newcastle disease virus & _Bruguiera cylindrica_ \\ (NDV) & _Exococaria agallocha_ \\ _Lumnitzera racemosa_ \\ _Rhizophora mucronata_ & \\ \hline \hline \end{tabular}
\end{table}
Table 2: Antiviral effects associated with extracts of halophyte plants.