Introduction
Coconut (Cocos nucifera L.) is a tropical palm which is aptly called ‘tree of life’ (kalpavriksha ) as it supplies wide range of food products of human consumption viz ., coconut oil, tender nut water, endosperm, inflorescence-sap derived sugar etc. Among this coconut oil has been attributed with many nutritional and health-conferring properties owing to its unique fatty acid composition (Dayrit 2014). The principal biochemical components of coconut oil and their potential health benefits are presented in Table 1 (Table 1 near here) . Coconut oil is rich in medium chain triglycerides (MCTs) due to the predominance of C6 to C12 fatty acids attached to the glycerol moiety. Coconut oil derived-MCTs are easily soluble and digestible by salivary and pancreatic lipases in comparison to triglycerides of other vegetable oils which are predominantly long chain triglycerides (LCTs). Lauric acid (C12) is one of the prime medium chain fatty acids (MCFAs) and its content in coconut oil varies from 45-53% (Dayrit 2014). Around 60% of the coconut triacyl glycerol (TAG) comprises MCFAs (both lauric acid and capric acid) in its positionssn-1 , and sn-3 (Dayrit 2014). Studies have demonstrated that proportion of dietary MCTs determines their mode of absorption as LCFAs predominantly enter the lymphatic system whereas MCTs are absorbed through portal veins (Mc Donald et al., 1980). Differential absorption of MCTs ensures their faster digestion, absorption and rapid energy expenditure thereby alleviating adiposity in humans (St-Onge et al., 2003). Besides their hypolipidemic effects, MCTs are known to have antimicrobial effects. Most conspicuously, lauric acid and its monoglyceride derivative, monolaurin, have been demonstrated to possess anti-microbial properties against gram positive bacteria (Projan et al 1994, Peterson et al., 2004), and many viruses such as Junin virus (JUNV), vesicular stomatitis virus, Simian immunodeficiency virus (SIV) etc. infecting humans (Thormar et al., 1987; Hornung et al., 1994; Bartolotta, et al., 2001; Duke 2009; Li et al., 2009). Administration of coconut oil has been found to be an effective remedy for the treatment of many of the enveloped viruses such as such as Cytomegalovirus, Epstein-Barr virus, hepatitis C virus, influenza virus, leukemia virus (Enig 2010; Dayrit 2000; Fife 2013). The antiviral property of monolaurin has been attributed to its common role in disrupting the phospholipid layers in the membranes of the enveloped viruses causing their ultimate disintegration. Monolaurin has adverse effects on the virus assembly and maturation phases of infection cycle eventhough the viral RNA and protein synthesis are unimpeded (Hornung et al., 1994). The binding of viral M protein (membrane) to the host cells was compromised due to the presence of lauric acid (Hornung et al., 1994). Supplementation of MCTs such as lauric acid induces cellular biosynthesis of triacylglycerols (TAG) in the infected cells (Hornung et al., 1994; Bartolotta, et al., 2001). This spurt in the biosynthesis of TAGs deprives the viruses of its crucial process, glycoprotein insertion in the plasma membrane, consequently interrupting the virus maturation process (Hornung et al., 1994; Bartolotta, et al., 2001). However, direct inactivation of virion particles of other enveloped viruses such as HIV and HSV due to physical contact with MCFAs is also not uncommon (Kristmundsdottir et al., 1999; Kohn et al., 1980). Antiviral properties of coconut oil-derived lauric acid or direct application of coconut oil have been established in animal studies. Administration of virgin coconut oil (VCO) through feed has enhanced the immunity parameters of chickens following challenge test with Avian influenza A virus subtype H5N1 (Yuniwarti et al., 2015).
COVID-19 (Coronavirus disease-2019), the pandemic caused by novel SARS Coronavirus (SARS-CoV-2) has been wreaking havoc in the global health sphere. At this point of time no specific drugs are therapeutic agents are prescribed to control the disease eventhough clinical trials are on-going. As the number of confirmed COVID-19 cases are increasing (3.517 million cases and death toll of 2,43,401 as on 5/ May/2020) (https://www.who.int/docs/default-source/coronaviruse/situation-reports/20200505covid-19-sitrep-106.pdf?sfvrsn=47090f63_2) lot of interests have been generated towards identification of compounds of plant origin with antiviral potential. These developments have renewed the interests in studying coconut oil and its variant virgin coconut oil (VCO) against COVID-19. Philippine Council for Health Research and Development (PCHRD) and Department of Science and Technology (DOST) has announced a hospital-based project entitled “Virgin Coconut Oil and Omega-3a Adjunctive Therapy for Hospitalized Patients with COVID-19” (https://www.covid19.gov.ph/dost-to-study-benefits-of-virgin-coconut-oil-on-covid-19-patients). In this context, this communication presents the pros and cons of developing the coconut oil and its products-based treatment for COVID-19 with special emphasis on biochemical basis of antiviral properties.