Relevance of ayurveda anti-viral herbal wisdom from the perspective of current researches

Due to COVID-19 outbreaks, entire humanity across the globe is suffering from this deadly disease and searching for novel and more effective antiviral herbal drug for its complete cure. Ayurveda compendia have described herbal medicines which are said to be effective against all microorganisms. Hence in this paper attempt is made to review Krimighna drugs described in Ayurveda compendia and identify its efficacy on various viral diseases. Relevant references were searched concerning krimihar drugs described in Brihatrayee viz. Charak Samhita, Sushruta Samhita and Ashtanga Hridaya. Scientific research papers related to pre-clinical and clinical studies showing the antiviral activity of individual krimighna drugs were also searched. In all Samhitas total, 56 drugs were found having Krimighna properties. Out of these only ten drugs are found to have antiviral activity against various type of viruses such as Herpes Simplex virus (HSV type 1 & 2), Dengue virus (DNGV), Newcastle Disease virus (NDV), Sindbis virus(SINV) Measles virus, Poliovirus. Herbal medicinal drugs have great potential to treat viral diseases. Considering the global disease burden caused by COVID-19, there is an urgent need to explore the Krimighna drugs with antiviral activity and to develop novel and useful antiviral agents to combat the COVID -19 menace effectively.


INTRODUCTION
Diseases caused by viruses are increasing worldwide and are becoming a great danger to humanity, causing pandemics throughout the world. COVID-19 outbreak is the latest in this series, and scientists and researchers are searching for novel and more effective antiviral drug for its complete cure. Coronavirus disease COVID-19 is caused by the recently discovered coronavirus serotype 2, which is zoonotic (spread through animals to humans) and now spreading human to human throughout the globe. It was irst reported in Wuhan city of Hubei province of China in December 2019 and soon spread across the world, causing thousands of lives (Goothy et al., 2020). Corona is an RNA virus causing respiratory morbidity like MERS-Middle East Respiratory Syndrome and SARS-CoV-2 Severe Acute Respiratory Syndrome (Rathi and Rathi, 2020).  Humans have been suffering from virus attacks since time immemorial. In recent decades, several viruses have been identi ied from animals to humans and triggered widespread outbreaks, resulted in thousands of deaths. There have been several signi icant pandemics recorded in human history, including smallpox, cholera, plague, dengue, AIDS, in luenza, West Nile disease and tuberculosis. In luenza pandemics (Qiu et al., 2017). In recent years have witnessed signi icant pandemics such as hantavirus pulmonary syndrome (HPS), severe acute respiratory syndrome (SARS), H5N1 in luenza, H1N1 in luenza, Middle East respiratory syndrome (MERS), and Ebola virus disease epi-demic (Gostin et al., 2016). COVID-19 is the latest pandemics in this chain. No vaccine or effective antiviral drug is yet discovered for the treatment of COVID-19 disaster. It was reported to be believed that few Ayurvedic medicines may alleviate the symptoms of COVID-19. AYUSH Department also published an advisory for the sake of public interest and advised to use culinary herbs, spices like turmeric and herbal tea with ginger to protect from the COVID-19 menace effectively (of Ayush, 2020). Ayurveda has given more emphasis on preventive care through Dincharya (daily regime) and Ritucharya (Seasonal regime) to maintain a healthy life. As there is no effective medicine discovered yet, In Ayurveda, Charaka Samhita has described Krimighna Gana (antimicrobial drugs) to combat with any viral infection. Later Sushruta Samhita, Astanga hridaya also described a speci ic group of herbal medications to tackle any bacterial, fungal or viral infectious diseases. Researches on few medicinal plants have shown potent antiviral activity without any side effects and thus facilitated to boost the individual's immune system (Kalyani and Kamaruz, 2013). Krimighna drugs also content pharmacologically active constituents in terms of phytochemicals, but their potency against antiviral diseases is yet to be assessed. Hence in the present paper, an attempt is made to review researches done on the Krimighna drugs described in Samhitas and to know its ef icacy on various viral diseases. This study may help to identify novel and more effective antiviral drugs to treat viral infections effectively.

MATERIALS AND METHODS
Relevant references were searched concerning krimihar drugs described in Brihatrayee viz. Charak Samhita, Sushruta Samhita and Ashtanga Hridaya. Published scienti ic research papers related to pre-clinical and clinical studies showing the antiviral activity of individual krimighna drugs were searched on Pub med, Scopus, Web of science, Medknow, Ayushdhara and google scholar by using relevant keywords regarding the antiviral activity of medicinal plants studied in last twenty-ive years.
In Ayurveda texts, the word Krimi is used frequently to denote worms or microbes and Drugs acting on these microbial agents have been termed as Krimighna Dravyas. According to the Shabda kalpadruma (An Encyclopedic dictionary of Sanskrit words), the word Krimi is derived from the root word "Kramana" which means attacking, surpassing or overcoming (Soni et al., 2017). Acharya Charaka has described 20 varieties of Krimi which include both internal and external krimis while Acharya Vagbhata described internal and external krimis with various shape, size and colour. Krimi can be compared in modern science with microorganism and macroorganism (Jain et al., 2018) Thus Ayurveda seers were very well aware of the presence of the microorganisms, their pathogenesis, symptoms and treatment.
The Krimi is a broad term which includes all types of worms and microbes. A microbe is a term for tiny creatures that individually are too small to be seen with the unaided eye. Microbes include bacteria, viruses archaea and fungi. A virus is a significant type of microbe, responsible for many infections that can only replicate inside the living cells of other organisms. Viruses can infect all kinds of living form such as human, animals, plants, and even microorganisms (Rajeevkumar et al., 2017). These viruses can spread the infection by coughing/ sneezing through droplet infection. These infections can also be spread through the use of contaminated food, water, bedsheets, utensils and ornaments, body luids such as blood and saliva. Acharya Sushruta termed such diseases as Aupasargik Vyadhis or Infectious diseases (Kalamkar et al., 2015). Remaining 13 drugs which are antimicrobial in nature but do not include in any group of Krimighna drugs in Samhitas have also shown antiviral activities in various researches. All these medicinal plants contain a wide variety of varied phytochemicals such as alkaloids, tannins, saponins, lavonoids, terpenoids, lignans, coumarins, and many other components which are supposed to be responsible for potent antiviral activity by inhibiting the replication cycle of various types of DNA or RNA viruses (Jassim and Naji, 2003;Ojo et al., 2009). Surprisingly, few plants which are not termed as Krimighna but have shown signi icant antiviral activity like Glycerrhaza glabra and Phyllanthus urinaria. Glycyrrhizic acid extracted from Glycerrhaza glabra exerts antiviral activity against Kaposi's sarcoma-associated virus by the elimination of the inactive form of the virus via apoptosis. Glycyrrhizic acid also inhibited the replication of SARS (Severe Acute Respiratory Syndrome) (Cinatl et al., 2003). The lavonoid Ellagic acid from Phyllanthus urinaria inhibits immunotolerance of mice against the hepatitis B virus e-antigen (Kang et al., 2006). Phyllan-thus urinaria extract markedly repress HBV replication and expression in an HBV transient transfection mouse model (Wu et al., 2015). In clinical trials conducted by Wang MX et al. in chronic hepatitis B patients demonstrated that Phyllanthus urinaria promotes HBeAg and HBeAb seroconversion from positive to negative (Wang et al., 1995;Zhong et al., 1998). The depressing thing is that modern antibiotics are not adequate to control viral infection. Though several drugs are identi ied as antiviral drugs against the speci ic virus but still a plethora of potentially useful krimighna drugs waiting to be evaluated and exploited with their antiviral activity. Hence young researchers have an opportunity to conduct in vitro and in vivo assays to evaluate the antiviral activity of these herbal drugs. If we could ind out the potential antiviral drug from these studies, it will be a boon for the entire world which can do wonder in the treatment of KOVID -19 the most dangerous pandemic of the decade.

CONCLUSIONS
The number of medicinal plants described in Ayurveda compendia as Krimighna drugs have shown remarkable antiviral activities against various viruses. However, due to the global disease burden caused by COVID-19, there is an urgent need to identify novel compounds with antiviral activity from the unexplored Krimighna drugs using modern in vitro assays. It is must involve well-established sciences such as Ayurveda, immediately into the mainstream of discovering a solution for any epidemic or pandemic situation to have all possible alternatives to discover the cure. The elucidation of active constituents in these plants may provide signi icant lead to the development of new and effective antiviral agents to combat the COVID-19 menace effectively.

ACKNOWLEDGEMENT
Author would like to thank DMIMSU for motivating and providing all necessary help for writing this article.

Con lict Of Interest
None.