Several hundred plant and herb species that have potential as novel antiviral agents have been studied, with surprisingly little overlap. A wide variety of active phytochemicals, including the flavonoids, terpenoids, lignans, sulphides, polyphenolics, coumarins, saponins, furyl compounds, alkaloids, polyines, thiophenes, proteins and peptides have been identified. Some volatile essential oils of commonly used culinary herbs, spices and herbal teas have also exhibited a high level of antiviral activity. However, given the few classes of compounds investigated, most of the pharmacopoeia of compounds in medicinal plants with antiviral activity is still not known. Several of these phytochemicals have complementary and overlapping mechanisms of action, including antiviral effects by either inhibiting the formation of viral DNA or RNA or inhibiting the activity of viral reproduction. Assay methods to determine antiviral activity include multiple-arm trials, randomized crossover studies, and more compromised designs such as nonrandomized crossovers and pre- and post-treatment analyses. Methods are needed to link antiviral efficacy/potency- and laboratory-based research. Nevertheless, the relative success achieved recently using medicinal plant/herb extracts of various species that are capable of acting therapeutically in various viral infections has raised optimism about the future of phyto-antiviral agents. As this review illustrates, there are innumerable potentially useful medicinal plants and herbs waiting to be evaluated and exploited for therapeutic applications against genetically and functionally diverse viruses families such as Retroviridae, Hepadnaviridae and Herpesviridae

Novel antiviral agents: a medicinal plant perspective

The plants of the genus Phyllanthus (Euphorbiaceae) are widely distributed in most tropical and subtropical countries, and have long been used in folk medicine to treat kidney and urinary bladder disturbances, intestinal infections, diabetes, and hepatitis B. In recent years, the interest in the plants has increased considerably. Substantial progress on their chemistal and pharmacological properties, as well as a few clinical studies of some Phyllanthus species have been made. This review discusses the current knowledge of their chemistry, the in vitro and in vivo pharmacological, biochemical, and clinical studies carried out on the extracts, and the main active constituents isolated from different species of plants of the genus Phyllanthus. These studies carried out with the extracts and purified compounds from these plants support most of their reported uses in folk medicine as an antiviral, in the treatment of genitourinary disorders, and as antinociceptive agents. However, well-controlled, double-binding clinical trials are lacking. Several compounds including alkaloids, flavonoids, lignans, phenols, and terpenes were isolated from these plants and some of them interact with most key enzymes. Together this data strongly supports the view that the plants belonging to the genus Phyllanthus have potential beneficial therapeutic actions in the management of hepatitis B, nefrolitiase, and in painful disorders.

A review of the plants of the genus Phyllanthus: their chemistry, pharmacology, and therapeutic potential.

Indian medicinal herbs as sources of antioxidants

Phenolic compounds from Brazilian propolis with pharmacological activities.

Fucoidans from the brown seaweed Adenocystis utricularis: extraction methods, antiviral activity and structural studies

An aqueous extract of the plant Phyllanthus niruri inhibits endogenous DNA polymerase of hepatitis B virus and binds to the surface antigen of hepatitis B virus in vitro. The extract also inhibits woodchuck hepatitis virus (WHV) DNA polymerase and binds to the surface antigen of WHV in vitro. The extract, nontoxic to mice, was tested for antiviral activity in woodchucks (Marmota monax). In a trial using six long-term WHV-carrier woodchucks, five treated animals showed a faster decrease in woodchuck hepatitis virus surface antigen titer compared to one untreated control. In animals recently infected with WHV, the extract was effective when administered i.p. in three out of four animals in reducing and within 3-6 weeks eliminating both the surface antigen titer and DNA polymerase activity in serum. The treatment was discontinued after 10 weeks, and the treated animals have remained free of detectable markers of WHV for more than 45 weeks. In contrast, three untreated controls remained positive for both markers for WHV. One of the controls died after 8 weeks; the other two controls have remained positive for WHV markers for more than 45 weeks. In a third trial with long-term carriers, test animals treated subcutaneously with the extract for 12 weeks did not respond; but on switching the mode of administration to i.p., two out of the five animals showed a significant decrease in woodchuck hepatitis virus surface antigen titer compared to controls.

https://www.pnas.org/content/pnas/84/1/274.full.pdf

Effects of an extract from Phyllanthus niruri on hepatitis B and woodchuck hepatitis viruses: in vitro and in vivo studies.

Hepatitis B virus and primary hepatocellular carcinoma: treatment of HBV carriers with Phyllanthus amarus.

A sulfated polysaccharide isolated from Pelvetia fastigiata, a marine algae, was found to inhibit in vitro the reaction of the surface antigen of hepatitis B virus (HBsAg) or of woodchuck hepatitis virus (WHsAg) with antibody to HBsAg (anti-HBs). The polysaccharide was composed mainly of 1----2 linked L-fucose-4-sulfate with some (less than 10%) 1----3 linkages. The inhibition of the reaction of HBsAg with anti-HBs or of WHsAg with anti-HBs was found to be directly proportional to the molecular size of the polysaccharide. Comparison of its inhibitory activity with that of carrageenans and dextran sulfates showed that, in addition to the size, the configuration of the component sugar and the presence of deoxy sugar may play a role in the inhibition of reaction of HBsAg or WHsAg with anti-HBs. The fucose sulfate polymer, fucoidan, however, had no effect in vivo on woodchuck hepatitis virus in woodchuck chronic carriers.

Interaction of Fucoidan from Pelvetia fastigiata with Surface Antigens of Hepatitis B and Woodchuck Hepatitis Viruses

On a mis au point un procede de traitement d'infection retrovirale par administration d'extrait de Phyllantus niruri. It has developed a retroviral infection treatment process by administering extract Phyllantus niruri.

Pinayur S. Venkateswaran

Papers

Effects of an extract from Phyllanthus niruri on hepatitis B and woodchuck hepatitis viruses: in vitro and in vivo studies.

Hepatitis B virus and primary hepatocellular carcinoma: treatment of HBV carriers with Phyllanthus amarus.

Interaction of Fucoidan from Pelvetia fastigiata with Surface Antigens of Hepatitis B and Woodchuck Hepatitis Viruses

Method of treating retrovirus infection

Phyllantus Species: Sources of New Antiviral Compounds