By Sri S.Rajamanickam
Asst.Chief Technical officer,ICAR-CIBA
Herbs play an important role in disease control because they contain active ingredients with antioxidant, antimicrobial, antistress, growth promotion, appetite stimulation, tonic and immunostimulation, and aphrodisiac properties.
1. Antioxidants:
Reactive oxygen species (ROS) formed in vivo, such as superoxide anion, hydroxyl radical and hydrogen peroxide, are highly reactive and potentially damaging transient chemical species. These are continuously produced in the human body, inasmuch as they are essential for energy supply, detoxification, chemical signaling and immune function. The ROS are regulated by endogenous superoxide dismutase, glutathione peroxidase and catalase. Induced by exposure to external oxidizing substances or a failure of defense mechanisms, an over-production of ROS causes damage to cell structures, DNA, lipids and proteins (Valko et al.2006) that increases the risk of more than 30 diseases (Aruoma 1998). Flavonoids and phenolic acids, widely present in higher plants, are effective against the deleterious effect of ROS. Some compounds in basil (Ocimum) possess strong antioxidant activity (Middleton and Kandaswami 1993). Cinnamon has antioxidant activity comparable to that of the synthetic antioxidant butylated hydroxytoluene (BHT) (Middleton and Kandaswami 1993).
2. Antimicrobials
Guava (Psidium guajava) has antibacterial activity against Vibrio and Aeromonas hydrophila at minimum levels of 1.25 and 0.625 mg/mL, respectively. Guava eliminates luminous bacteria from black tiger shrimp (Penaeus monodon) more effectively than oxytetracycline (Direkbusarakom 2004).
Ethanol, methanol and hexane extracts of basil Ocimum basilicum were investigated for their in vitro antimicrobial properties against 146 microbial organisms, including aquaculture pathogens. The hexane extract had a stronger and broader spectrum of antibacterial activity than other extracts (Adigüzel et al. 2005).
Indian almond Terminalia catappa extract is an alternative antibacterial remedy against tilapia ectoparasites and the bacterial pathogen A. hydrophila. Growth of two strains of A. hydrophila was inhibited at 0.5 mg/mL (Chitmanat et al. 2005).
Enriching Artemia nauplii with methanol extracts of Solanum trilobatum, Andrographis paniculata and Psorolea corylifolia reduced Vibrio load in black tiger shrimp post-larvae. Similar results were obtained from inoculation challenge with other pathogens, including Pseudomonas aeruginosa, Staphylococcus aureus and Salmonella typhi. Immanuel et al. (2004) studied the bacterial load of Indian white shrimp (P. indicus) juveniles fed with seaweed and herbal extracts and reared in water inoculated with Vibrio parahaemolyticus.
Austin et al (1992) reported a kind of micro algae (Tetraselmis suecica), which can inhibit pathogenic bacteria of fish. Teraselmis suecica was observed to inhibit Aeromonos hydrophila, A. salmonicida, Serrstia liquefaciens, Vibrio anguillaram, V. salmonicida and Yersnia ruckeri type I. When used as a food supplement, the algal cells inhibited laboratory-induced infection in Atlantic salmon. When used therapeutically, the algal cells and their extracts reduced mortalities caused by A. salmonicida, A. liquefaciens, V. anguillaram, V. salmonicida and Yersnia ruckeri type I. They suggested that there may be some bioactive compounds in the algal cells, and there appears to be a significant role for Tetraselmis in the control of fish diseases.
OCIMUM BASILICUM exhibits in vitro antibacterial activity against Bacillus subtilis, E. coli, Pseudomonas auerginosa, and Staphylococcus aureus. Strong activity was also shown against Candida albicans.
ROSMARINUS OFFICINALIS contains some of the most powerful candida killing substances available.
GARLIC EXTRACT were found to be effective antibiotic agents against many bacteria, including Staphylococcus aureus, Escherichia coli, salmonella enteritidis, Klebsiella pneumoniae, and mycobacteria.
Rosemary contains camphor, a powerful anti-microbial. Thyme contains thymol, which clinical studies have shown to kill staphylococcus and salmonella. Lavender contains antibacterial compounds that are more concentrated than many chemical components used cleansers, like phenol, and sage contains natural phenol.
3. Liver stimulants
Eclipta alba, Swertia chirraita, Andrographis peniculata etc are well known hepato protectors.
Hundreds of research studies, mostly in Europe, have confirmed the remarkable ability of milk thistle to protect the liver against virtually all types of damage: from accidental exposure to chemical pollutants, toxic side effects of medications, liver diseases like hepatitis, and even the self-inflicted damage from overindulgence in rich food and alcohol.
4. Appetizers:
Hot spices from peppers (such as capsaicin and piperine) and other essential oils (such as cinnamon, which supplies cinnamaldehyde) stimulates amylase production. They can stimulate appetite, thereby increasing food consumption and conversion efficiencies. Increases in enzyme production can result in improvements in digestibility and availability of nutrients from feedstuffs (Chesson 1987). Reducing the amount of undigested material limits the substrate available for proliferation of pathogenic bacteria. The growth promoter characteristic of herbals induces transcription, leading to increased protein synthesis.
Eclipta alba is commonly used as a deobstruent to promote bile flow and to protect the liver parenchymal tissue in viral hepatitis and other conditions involving hepatic enlargement. The fresh juice of the leaves is given in the treatment of edema, fevers, liver disorders, and rheumatic joint pains; it is also used to improve the appetite and to stimulate digestion.
According to Ayurveda, Swertia Chirraita is a bitter tonic, stomachic. It is useful in liver disorders, eyes, heart. A strongly bitter tonic it is an excellent remedy for a weak stomach, especially when this gives rise to nausea, indigestion and bloating and it has also been shown to protect the liver.
Phyllanthus niruri has been found to exhibit inhibitory effect on hepatitis B virus evident by its exhaustive utility in cases of chronic jaundice. 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.
Effect of Phyllanthus niruri extracts on woodchuck hepatitis virus surface antigen was also observed in a study of rats.
5. Antivirals
Black tiger shrimp fed ethanol extract of Clinacanthus nutans leaves and exposed to yellowhead virus (YHV) had 95 percent survival rates compared to 25 percent survival in the no-extract (control) group (Direkbusarakom et al. 1996).
Methanol extracts of five different herbal medicinal plants, such as Cynodon dactylon, Aegle marmelos, Tinsospora cordifolia, Picrorhiza kurroa and Eclipta alba, were incorporated into a diet for WSSV-infected shrimp. Better values of haematological, biochemical and immunological parameters were found in shrimp fed a diet that incorporated immunostimulants (Citarasu et al. 2006).
In Mexico, Elizabeth Cruz-Suárez and colleagues show that fucoidan, extracted from the brown algae Cladosiphon okamuranus was effective against WSSV in Litopenaeus vannamei
The antiviral effect of sulfated polysaccharides extracted from marine algae against mammalian viruses in vitro is well known (Witvrouw and De Clercq, 1997). Both Spirulina platensis (Hayashi and Hayashi, 1996) and S. maxima (Hernández-Corona et al., 2002) have antiviral activity. Sulfated fucans (fucoidan) can be isolated from 43 species of brown algae. Fucoidans from brown algae are extremely complex and heterogenous in structure (Berteau and Mulloy, 2003). In a study, fucoidan extracted from marine algae Sargassum polycystum was incorporated in a diet. The diet was fed to P. monodon juveniles for four days before and after challenge with WSSV. Shrimp receiving the highest amount of fucoidan in the diet (100, 200 and 400 mg/ kg body weight of shrimp) showed increased survival rate (Chotigeat et al., 2004).
Seed extract of Pongamia pinnata plant has antiviral activity against herpes simplex virus (Elanchezhiyan et al., 1993). An ethanolic extract bis(2-methylheptyl)phthalate from P. pinnata leaves was incorporated in a diet and tested for antiviral activity against WSSV infection in P. monodon. P. monodon were fed for 4 days before and 15 days after WSSV challenge (200 and 300 μg/g body weight of shrimp/ day). Increased survival (40 to 80%) was found with the diet containing the highest concentration of the extract (Ramesthangam and Ramasamy, 2007). Increased survival of P. monodon was also observed after administration of a mixture of WSSV and extracts of Aegle marmelos, Cynodon dactylon, Lantana camara, Mimosa charanita, Phyllanthus amarus plants (Balasubramanian et al., 2007). The mechanisms of the antivial activity of these plant extracts against WSSV are not known.
Extracts of plants (Cyanodon dactylon, Aegle marmelos, Tinospora cordifolia, Picrorhiza kurooa, Eclipta alba) (Citarasu et al., 2006) have been shown to improve the immunity and reduce the mortality of WSSV infected shrimp. The mechanism was attributed to an activation of innate immunity.
6. Antifungal Activity
Infection by molds Aspergillus flavus and Fusarium oxysporum can be controlled with basil (O. basilicum) extract (Adigüzel et al. 2005).
A DMSO extract of Tamarix dioica has significant activity against A. flavus and moderate activity against F. solani (Khan et al. (2004).
Rhazya stricta is a small glabrous shrub that has antifungal effects against Trichophyton longifusis, A. flavus, Candida albicans and F. solani.
7. Antistress Activity
Various herbs, Withinia somnifera, Emblica officanalis, Asparagus racemosus, Ocimum sanctum, Tribulus terresttris and Piper longum, are claimed to have adaptogenic, anabolic effects and the ability to improve vital energy.
Picrorhiza kurroa, used as an antistress compound for shrimp (Citarasu et al. 1998).
Rutin is a bioflavonoid extracted from Toona sinensis with strong antioxidant and antistress activity in crustaceans. Rutin has improved the biochemical, immunological and haematological response to stress in Litopenaeus vannamei caused by Vibrio alginolyticus (Hsieh et al. 2008).
8. Immunostimulant Activity
There is a growing interest in using medicinal herbs as immunostimulants in aquaculture, including extracts of Glycyrrhizin, Emblica officinalis, Cynodon dactylon, Adathoda vasica, O. sanctum, W. somnifera and Myristica fragrans, Aegle marmelos, T. cordifolia, P. kurooa and E. alba against pathogenic bacteria and viruses such as Vibrio harveyi and A. hydrophila infected fish, and WSSV-infected shrimp.
9. Gas Adsobtion:
It is well known that saponins from Yucca siddagere and Methi can adsorb Hazardous gases that arise in aquaculture ponds.
10. De-worming activity:
Studies are available from various parts of the world wherein the anthelmintic efficacies of some of the plants reported also in this survey have been carried out. For example Kashiya [15], observed a significant decrease in faecal egg counts in animals treated with dried leaves of Acacia nilotica (P < 0.05) and also reported a reduction of 34% in worm burdens in animals treated with Acacia karoo. Khobragrade [16] reported a complete cessation of motility of Bunostomum trigonocephalum worms after exposure to crude aqueous extracts of Allium sativum. Such an activity has also been reported for some plants like that of Chenopodium album, Sorghum extract [17], Allium sativum, Zingiber officinale, Cucurbita mexicana and Ficus religiosa [18]. Seeds of Peganum harmala contain an active constituent-Tetra-hydro-harmin that has been claimed to be active against mixed gastrointestinal nematode infection in goats [19]. The anthelmintic activity of plant extracts can be either due to direct action of extract on the worms or through induction of GI irritation and diarrhoea, which causes dislodgment of resident worms. Plants that appear to have direct anthelmintic action include A. absinthium and C. ambrosioides that in vivo cause severe GI irritation and in vitro cause paralysis and ultimately death of worms. Chemical analysis of A. absinthium has shown that its volatile oil is rich in thujone (α and β), which has been earlier reported as an anthelmintic [20]. In Turkish folk medicine, A. absinthium has also been used as an anthelmintic, besides its other uses such as antipyretic, antiseptic, tonic, diuretic and for the treatment .
