# Halophytes as Medicinal Plants against Human Infectious Diseases
## 3 Halophytes as a Source of Antimicrobial Compounds
### Antibacterial Effects  
Many haplotypes have been screened for antibacterial effects (Table 3). Extracts obtained with various solvents from different plant parts have been tested against a variety of Gram-positive and Gram-negative bacteria commonly associated with urinary, intestinal, respiratory and skin infections in humans. \begin{table}
\begin{tabular}{c c c} \hline
**Virus** & **Plants Species** & **Reference** \\ \hline Vaccinia virus & \begin{tabular}{c} _Bruguiera cylindrica_ \\ _Lummittizera racemosa_ \\ _Rhizophora mucronata_ \\ _Ceriops decandra_ \\ \end{tabular}  \\ \hline Encophalomyocardiitis virus & \begin{tabular}{c} _Avicennia marina_ \\ _Bruguiera cylindrica_ \\ _Exocoeraria agallocha_ \\ _Lummittizera racemosa_ \\ _Rhizophora apiculata_ \\ _Rhizophora lumarckii_ \\ _Rhizophora mucronata_ \\ _Salicornia brachiata_ \\ \end{tabular}  \\ \hline Semliki Forest virus (SFV) & \begin{tabular}{c} _Bruguiera cylindrica_ \\ _Ceriops decandra_ \\ _Aegiceras cornicultatum_ \\ _Rhizophora lamarckii_ \\ _Rhizophora mucronata_ \\ \end{tabular}  \\ \hline Hepatitis B virus (HBV) & \begin{tabular}{c} _Acanthus licidelius_ \\ _Aegiceras cornicultatum_ \\ _Avicennia marina_ \\ _Bruguiera cylindrica_ \\ _Ceriops decandra_ \\ _Rhizophora apiculata_ \\ _Rhizophora lamarckii_ \\ _Salicornia brachiata_ \\ _Sesuvium portulacastrum_ \\ \end{tabular}  \\ \hline Human immunodeficiency virus (HIV) & \begin{tabular}{c} _Aegiceras cornicultatum_ \\ _Ceriops decandra_ \\ _Exocoeraria agallocha_ \\ _Rhizophora apiculata_ \\ _Rhizophora lamarckii_ \\ _Rhizophora mucronata_ \\ \end{tabular}  \\ \hline Herpesviruses (HSV-1, HSV-2) & \begin{tabular}{c} _Plantago major_ \\ _Limonium densifporum_ \\ _Plantago major_ \\ _Rhizophora lamarckii_ \\ _Rhizophora mucronata_ \\ \end{tabular}  \\ \hline \begin{tabular}{c} Herpesviruses \\ (HSV-1, HSV-2) \\ \end{tabular}  & \begin{tabular}{c} _Plantago major_ \\ _Limonium densifporum_ \\ _Plantago major_ \\ _Plantago major_ \\ _Rhizophora lamarckii_ \\ _Rhizophora mucronata_ \\ \end{tabular}  \\ \hline \ \begin{tabular}{c} Herpesviruses \\ (HSV-1, HSV-2) \\ \end{tabular}  &
\begin{tabular}{c} _Plantago major_ \\ _Limonium densifporum_ \\ _Plantago major_ \\ _Elmonium densifporum_ \\ _El  
Persistent infections are commonly associated with bacterial biofilms, which normally exhibit enhanced resistant to antibiotics. Molecules that interfere with quorum-sensing communication (anti-quorum sensing, anti-QS) reduce biofilm development and make bacteria more susceptible to antimicrobials, being therefore used as coadjutants in antimicrobial chemotherapy [77]. Some halophytes (e.g., _Rhizophora annamalayana_ Kathiresan) express metabolites with anti-QS activity against the biological models of _Chromobacterium violaceum_ and _Vibrio harveyi_[78]. Ethanol extracts of the fruits of the facultative halophyte _Salvadora persica_ L., containing gallic, chlorogenic and caffe acids, inhibited biofilm development in oral _Staphylococcus_ strains [79]. Ether extracts of _Salicornia europaea_ L. inhibited _Bacillus cereus_, _Enterococcus faecalis_, _Escherichia coli_, _Microoccus luteus_, _Salmonella typhimurium_, _Serratia marcescens_ and _Staphylococcus epidermidis_. Interestingly, the water and acetone extracts had no significant antibacterial activity [80]. A study of the antibacterial properties of _Excoecaria agallocha_ L. confirmed the influence of the solvent on the efficiency of the extract. Methanol extracts of leaves exhibited the highest activity, whereas hexane and chloroform extracts had no activity at all [81]. This indicates that antibacterial effects are closely related to specific metabolites that are selectively extracted. Regardless of the solvent, extracts are mixtures of different metabolites that may interact to attain higher inactivation yields than equivalent concentrations of pure compounds.