Antiviral Plant Extracts

Herbal therapy has been an important part of health and wellness for hundreds of years. The renewed interest in medicinal plants has focused on herbal cures among indigenous populations around the world. Recent surveys have indicated that worldwide people now make more visits to healthcare professionals who spe-cialize in alternative medicine than to doctors who practice conventional medicine. It is hoped that extracts from herbs will add new medicinal plants to the world’s pharmacopoeia before they are lost forever that too particularly against viral infection. Based on the ethnobotanical data and the information collected from Siddha/ Ayurvedic practitioners of India, extracts obtained from Boerhavia diffusa , Eclipta alba and Phyllanthus amarus will be having great potential in curing various viral infections.


Introduction
For hundreds of years, herbal therapy has played a major role in maintaining the health and wealth of people around the world. For treatment of various illnesses, herbs are widely used. In most of the developing countries, nowadays, people prefer alternative medicine than conventional medicine indicated by a recent survey. Many publications and books claim the proficiency of herbs for the treatment of various illnesses including cirrhosis, hepatitis, and other deadly diseases. It has been observed widely that the medicinal plants and traditional medicines are used as a normative basis for maintaining good health [1].
In the process of developing many drugs, an increasing demand for the use of medicinal plant-derived products in the industries has been found [2]. For personal health maintenance, herbal remedies have become more popular in treatment of minor ailments. Due to increasing demand, there is a great risk that the existing medicinal plants on earth might disappear. Thus an important component of the health care system in a country like India is medicinal plants.
Chemical compounds obtained from plant source are termed as secondary plant products. Alkaloids and glycosides are the two major compounds present. In 4000 plant species, more than 3000 alkaloids have been identified. The difference between a toxic and medicinal effect of many alkaloids depends upon the dosage. When a sugar molecule gets attached to component which is active, it is called as glycoside which is categorized by the nature of the active component or nonsugar.
Clinical research of the present era has confirmed the ability of many medicinal plants in treating various viral diseases, while many recent scientific research have discovered the exact mechanism by which many different plants provide their therapeutic advantages. Three such plants are Boerhavia diffusa, Eclipta alba and Phyllanthus amarus.

Boerhavia diffusa
Boerhavia diffusa is a herbaceous plant commonly known as punarnava in Sanskrit. The whole plant is known to have medicinal properties and being used in most parts of the subcontinent. Alkaloids are best known principle product present in the roots which is known as punarnavine. In traditional medicine, Boerhavia diffusa is more commonly used in the treatment of jaundice, dyspepsia, abdominal pain, spleen enlargement and as an antistress agent. In the year 1980-1991, researchers proved that B. diffusa root extract had strong antihepatotoxic properties which can be used to cure viral hepatitis [3].

Origin and distribution
B. diffusa is found mostly in Asia, that too in warmer parts with an altitude of 2000. It grows well in crop fields and wastelands after the rainy season [4]. The genus Boerhavia has many species, and is also found spread in few regions of the world. B. diffusa is found in few places of Australia, South Africa and USA apart from Asian countries like China, Egypt, Pakistan, Sudan, Sri Lanka and in several countries of the Middle East [5]. Out of the 40 species of this genus, 6

Chemical constituents
The main component 2-glucopyranose-4-hydroxy-5-[P-hydroxyphenyl]propionyldiphenyl methane was found in the roots of the plant. Many steroids, triterpenoids, alkaloids, flavonoids, lipids, lignins, proteins, carbohydrates and glycoproteins are mostly found [7]. Punarnavine, hypoxanthine 9-L-arabinofuranoside, ursolic acid, boeravinone, punarnavoside and liirodendrin have been purified and elucidated in detail for their biological activity with antiviral properties. Large amount of potassium nitrate is mostly found in this plant. The entire plant has huge percentage of proteins and fats. It also contains 14 amino acids in root, out of which 7 are essential amino acids. Punarnavoside is an antifibrinolytic compound isolated from the roots of B. diffusa long back [8]. When roots were analyzed for phytochemical screening, maximum alkaloid content [2%] was found. DOI: http://dx.doi.org/10.5772/intechopen.85126

Pharmacology
Pharmacological studies have demonstrated strong antiviral properties. Wide diuretic properties have been found in punarnavoside obtained from Punarnava, apart from that anthelmintic, antifibrinolytic, anticonvulsant, antibacterial, antihepatotoxic, antiasthmatic and antinematodal activity have also been observed. Against various abnormal production of liver enzymes AST, ALT and pigment bilirubin, the aqueous root extracts of B. diffusa at a dose of 2 ml/kg exhibited strong protection [9].
Drugs obtained from this herb, given either alone or in combination with other drugs were found to be effective in killing many virus for disorders pertaining to liver, infections of the respiratory tract and heart disease [10]. Against various bacteria, the purified form of glycoprotein obtained from B. diffusa exhibited strong antimicrobial activity. Many clinical researches have proved that against bacteriophages punarnava is found to be very effective [11]. For inducing systemic resistance in various crops against different viruses, the roots of B. diffusa are used [12].

Antiviral activity of Boerhavia diffusa
Against potato virus X, Boerhavia diffusa have shown a very good effect in inhibiting in hypersensitive and systemic hosts. The inhibition of these extracts was found to be very sensitive to actinomycin D. By the application of the aqueous root extract of B. diffusa, the destructive yellow mosaic disease of mung bean [Vigna radiata], caused by mung bean yellow mosaic virus was controlled. The treatment also resulted in increased plant height, root nodulation, primary and secondary branches, grain yield and pod formation. Against bacteriophage, the purified form of glycoprotein obtained from Boerhavia diffusa showed strong antimicrobial activity. To resist viral infection in many susceptible crops, the extracts obtained from the roots of B. diffusa was used. This antiviral agent was active against Nicotiana tabacum, Sunhemp and Crotalaria juncea [13].

Eclipta alba
Eclipta alba grows as a weed commonly in wet places around the world. It is widely distributed in India, China, Thailand and Brazil. Eclipta alba [L.] Hassk.
[syn. Eclipta prostrata L.], commonly known as False Daisy is a plant from the family Asteraceae. Different varieties of indigenous drugs possessing analgesic properties have been obtained from this plant in Ayurveda. Extract of E. alba showed strong analgesic properties [14].

Origin and distribution
In the tropical and subtropical regions of the earth. Eclipta alba is usually found on poorly drained wet areas, on the dikes of rice paddies, along streams and ditches in marshes. It is most commonly found in elevated lands with 1200 mm of rainfall or more. It grows very well in salty and humid conditions but is mostly a plantation crop [15]. In few countries, it is found near sea level and is said to be a naturalized weed in waste places, open fields often near ditches and in cultivated areas [16]. In some parts of the world, it is a common plant of foreshores, streamsides, wet situations, weed of wet pasture and in roadside ditches. In is also found in low altitudes [17].

Pharmacology
In Ayurveda and in traditional Chinese herbal medicine, this species is widely used. It is used as liver tonic, rejuvenative and also widely used for better growth of hair [20]. The whole plant is used as ophthalmic, purgative, astringent, deobstruent, depurative, emetic, febrifuge, tonic and styptic. It is used internally for the treatment of anemia and diphtheria, dropsy and liver complaints [21], tinnitus, premature greying of the hair and tooth loss. It is also widely used for many external applications like oil for hair loss, dermatitis, wounds and even for athlete's foot [22]. For treating scorpion stings, its leaves are used. The plant juice is widely used for catarrhal problems and for those having increased production of bilirubin.
At the time of flowering, this plant is mostly harvested and is dried for further use. The roots are purgative and emetic. In cattle, it act as antiseptic to cure ulcers and wounds. In Ayurvedic medicine, the leaves of this plant are used a liver tonic. The dye produced from E. alba is most widely used for the purpose of tattooing [23].
To treat eczema and dermatitis, E. alba is widely used. In China and Brazil, it is also used as antivenom against snakebite. To reduce the inflammation of spleen and liver on few occasions, E. alba was used and found to be effective. Antiviral activity particularly in inhibiting Ranikhet disease virus, the alcoholic extract of the plant was proved to be very effective. To promote bile flow and protect the parenchyma, it is commonly used in viral hepatitis. This plant was widely used for antiaging too. In case of debility, the tonic obtained particularly from Eclipta alba is used. For minor cuts, burns and for inflammation, it is used externally. In children with upper respiratory, eye and ear infection, the leaf juice is mixed with honey. In the treatment of cirrhosis of the liver and infectious hepatitis, E. alba is used in the phytopharmaceutical formulations of medicines [24]. For rattlesnake bite, wedelolactone obtained from this plant is used. The shoot extract shows antimicrobial activity against Gram-positive bacteria Staphylococcus aureus and Gram-negative bacteria Escherichia coli.

Antiviral activity of Eclipta alba
Against many viruses, the extracts of Eclipta alba were proved to have strong antiviral activity [25]. Though the fresh juice of leaves is used for various benefits DOI: http://dx.doi.org /10.5772/intechopen.85126 like increasing appetite, mild bowel regulator, it is mainly used in viruses causing blood borne hepatitis. It is also used to protect the parenchyma and to promote bile flow which is popularly used to enhance learning and memory. In most parts of the subcontinent, it is used for jaundice, as a deobstruent and cholagogue in hepatic injury and other ailments of liver. One of the most potent inhibitory activity against HIV-1 integrase [HIV- 1 IN] was found in the water extract of Eclipta prostrate [26].

Phyllanthus amarus
In Ayurveda, Phyllanthus amarus is an Indian herb that has been used in support liver. 'Phyllanthus' is also represented by the name "leaf and flower" as the fruit and the flower are found under the leaf [27].

Origin and distribution
In all tropical regions of the planet, P. amarus is widely distributed. The exact geographic origin of this plant was not found by Paleobotanical studies [28,29]. This plant may be indigenous to the tropical Americas and also to the Philippines or India [22].

Chemical constituents
Some of the secondary metabolites that are present in P. amarus include lignins alkaloids, hydrolysable tannins, flavanoids, and polyphenols. Such phytochemicals and their structure were usually determined by using IR, UV, NMR and mass spectroscopy [30]. Apart from that, preparative thin layer chromatography and column chromatography are also used by which few new alkaloids were isolated [31].

Pharmacology
Parts of this plant P. amarus, mostly fresh and occasionally dry are sold and the decoctions are used widely for herbal baths. To treat bladder and kidney disorders, herbal decoction of this plant is used in traditional medicine [32]. This herb can also be used as tonic and can also be used as an appetizer. P. amarus plant extracts is also used as blood purifiers. It also helps to release phlegm for light malaria fevers and anemia [33]. In combination with many other herbs, this herb is used for curing flu, asthma and fever. The leaves are boiled and used to treat dysentery and even skin disorders [34]. For constipation also, studies have proved that extracts are very effective. Apart from that, extracts have even shown anticancer properties. It also has beneficial effects on liver functions. Several studies in the past have proved that P. amarus inhibits the activity of the HBsAg [35]. Widespread studies on P. amarus have showed that the extracts possess strong antiviral activities particularly against HBV and HCV. In Indian system of medicine, a chemo-biological fingerprinting methodology for standardization of P. amarus preparation was even patented [36].

Antiviral activity of Phyllanthus amarus
Evaluation of antiviral activity of Phyllanthus species was evident from aqueous extract showing strong activity against viruses like HSV1 and HSV2 in vero cells by quantitative polymerase chain reaction. To study protein expressions of treated and untreated infected vero cells, western blot and 2D-gel electrophoresis were most widely used. Phyllanthus amarus along with Phyllanthus urinaria demonstrate the strongest antiviral activity against both HSV1 and HSV2 viruses which is proposed to its action in the early stage of replication and infection [37].
In conclusion, in the existing scenario, there is an essential need for the development of new antiviral drugs. As on date there are many epidemiological studies that have evaluated different targets of these antivirals and promising results were obtained. Still a lot of research is needed to find out the actual potential for human use. In comparison to synthetic counterparts, extracts obtained from Boerhavia diffusa, Eclipta alba and Phyllanthus amarus are tend to be safer, very effective and cheap. The extracts obtained from these plants might have compounds that are true antiviral, but are present at insufficient quantity to inactivate all infectious virus particles. It is very much possible that obtaining active constituents from these plants will be providing many useful leads in the development of effective antiviral agents. Thus there is an urgent need to find effective antiviral agents as the existing drugs may be effective but in a specific manner. Based on the existing knowledge of traditional medicine, these three plants have to be explored further for formulating effective drugs against various dreadful disease caused by viruses.