ABSTRACT (HEAVY METAL TOXICITY OF ALLIUM SATIVUM IN THE COVID-19 ERA: A COMPARATIVE STUDY OF TWO STATES IN NIGERIA)

Since the outbreak of COVID-19, Nigeria has witnessed a steady increase in the consumption rate of garlic both in concentration and frequency because it boosts immunity. The question however is how safe is garlic? The aim of this study was to determine the concentration of five (5) heavy metals which include; Arsenic, Cadmium, Lead, Mercury, and Nickel in garlic samples obtained from nine (9) towns in Akwa Ibom state and two (2) towns in Enugu state, Nigeria. Samples were obtained from the local markets in 11 towns and a total of 55 samples (5 from each town) were purchased and analyzed using the Atomic Absorption Spectrophotometer after acid digestion. Data analysis of the heavy metal results were performed using the SPSS. Then data obtained was used to evaluate Estimated Daily Intake of the heavy metals, Hazard Quotient and Hazard Index. Levels of heavy metals ranged from 0.0009-0.7926 for arsenic, 1.3874-3.5332 for cadmium, 0.00156-0.2014 for lead, 0.0009-0.00136 for mercury and 0.8294-2.4940 for nickel for Akwa Ibom State and 0.0009-0.1892 for arsenic, 3.2514-3.4572 for cadmium, 0.00376-0.00456 for lead, 0.00114-0.00134 for mercury and 1.69375-3.0760 for nickel for Enugu State all in mg/kg. Hazard quotient for cadmium and arsenic were greater than 1 in both states but nickel was greater than 1 only in Enugu State. Hazard quotient for lead and mercury were less than one in both states. Hazard index of both states are greater than one. Results show that despite the health benefits of using garlic in the COVID-19 era, subjects are also predisposed to potential health hazards

INTRODUCTION (CHAPTER ONE)- HEAVY METAL TOXICITY OF ALLIUM SATIVUM IN THE COVID-19 ERA

Medicinal plants are plants which, in one or more of its organs contain substances that can be used for therapeutic purposes or as a precursor for the synthesis of useful drugs (Sofowora, 1982).

The medicinal value of plants has been known from ancient times and their uses have been scientifically proven by research. Prior to the advent of orthodox medicine, several ailments were treated with tea made from the bark of a Willow tree. Further research has shown that Willow’s bark contains salicylic acid; the active ingredient in aspirin (Micheal and David, 2017).

It has also been established that the plants which naturally synthesize and accumulate some secondary metabolites like alkaloids, glycosides, tannins, volatile oils, minerals and vitamins possess medicinal properties.

Allium sativum, commonly known as garlic, is one of the species in the onion family, Alliaceae. Garlic is a small perennial herb cultivated throughout West Africa, West Indies and Brazil. There are about 400 species. Garlic is among the oldest of all cultivated plants and is popularly ingested for both culinary and medicinal purposes (Gernot, 2005). Garlic is a plant of economic importance and is produced in high demand in the Northern regions of Nigeria where it is consumed both in raw and cooked form (Sofowora, 1982). The use of Garlic for medicinal purposes varies from usage for abdominal discomfort, diarrhea, otitis media and respiratory tract infections in Nigeria (Jaber et al., 2007), to treatment of common colds, hay fever and asthma in Europe and India. In Russia, Garlic is commonly used both as topical and systemic antimicrobial agent (Timbo et al., 2006).

In 1858, Louis Pasteur observed garlic’s antibacterial activity, and it was used during World Wars I and II as antiseptic on gunshot wounds to prevent gangrene (Tattelman, 2005). More recently, a clinical trial showed that mouthwash containing 2.5% fresh garlic was associated with good antimicrobial activity. However, a significant number of participants reported an unpleasant taste and halitosis (Groppo et al., 2007). Garlic is used to reduce abnormal cholesterol and blood pressure levels. Previous investigational studies in humans, have suggested possible cardiovascular benefits of garlic (Sonova and Sova, 2004).

           The discovery of a novel coronavirus that caused a new infectious disease termed Coronavirus disease of 2019 (COVID-19), first appeared in Wuhan, China in late December 2019 (Wang et al., 2020). The outbreak spread worldwide as a result of easy human-to-human transmission; this led to the declaration of the outbreak as a global pandemic by the World Health Organisation (WHO) on March 11, 2020.

The worldwide outbreak of COVID-19 had people’s lives put on hold; normalcy was snashed away, the world’s economy was largely impacted as it claimed over 436,167 lives globally as of June 15, 2020 (Verity et al., 2020). The number of cases and deaths increased daily resulting in chaos, as fear and panic gripped the masses. Individuals infected with the virus mostly experienced respiratory tract symptoms, such as cough and dyspnea, as well as fever. Although most infected individuals experienced only moderate respiratory illness and recovered without requiring specific treatments, while the elderly with underlying chronic conditions such as diabetes, heart disease etc, came down with serious medical complications and some, unfortunately met with death (WHO Coronavirus, 2020). Individuals who recovered without requiring specific treatments were reported to have had a stronger immune system, which enhanced their recovery. This led to an increase in the consumption of dietary supplements such as herbs, spices and nutrients (like garlic, ginger, liquorice, curcumin etc), as people believed it would boost and strengthen their immune system against the deadly virus. Positive outcomes were got from studies focused on the use of nutrients and herbs for enhancing immunity against COVID-19 (WHO briefing, 2020)

Garlic as one of the predominantly used medicinal plants, has been proven to possess an efficient natural antibiotic activity against a wide spectrum of bacteria and viruses; the immunomodulatory effects of this healthy spice is due to the presence of Organosulfur (e.g., allicin and alliin) and flavonoid (e.g., quercetin) compounds. The viral replication process is accelerated with the main structural protease of SARS-CoV-2. The formation of hydrogen bonds between this serine-type protease and garlic bioactives in the active site regions inhibits the COVID-19 outbreak. However, the overuse of these herbs is harmful to health (Luxita, 2020; Bo Han and Ba Hoang, 2020).

Heavy metals are natural constituents of the earth’s crust, but indiscriminate human activities have drastically altered their geochemical cycles and biochemical balance. From past decades, there has been a growing concern due to increased environmental pollution by the rapid urbanization, population growth, and intense industrialization. In recent years, heavy metal contamination has gained global attention, mainly because of the toxicological risks posed by such metals to human health (Ayodeji and Olorunshola, 2011). The primary sources of metals are fossil fuel burning, mining, smelting of metals and ores, application of synthetic fertilizers and pesticide in agriculture, improper disposal of contaminated water, municipal and sewage waste, industrial residues and vehicular emissions (Liliane et al., 2016). Increased concentrations of heavy metals in the air, soil, and water threaten human health both directly and indirectly via accumulation in the food chain. Although trace amounts of some metallic elements are essential for human health, they become toxic when they exceed permissible limits (Elekes et al., 2010).

Plants are good accumulators of heavy metals; they can accumulate much higher concentrations than the metal present in the environment. Hence, due to the great ability of bioaccumulation of heavy metals in the plant, they increase the risk potential to health (Rao and Meena, 2011).

           Heavy metals such as Pb, Cd, As, and Hg are non-essential and more toxic to the plants and possess no significant use in the biological system (Ji et al., 2012). Whereas, heavy metals such as Cu, Zn, Fe, and Co are essential for in trace amounts for the regulation of enzyme, vitamin synthesis, and hemoglobin formation in humans. But high concentrations result in damage to the central nervous system, liver, heart, kidney, and brain, which further leads to hypertension, skin infections, intestinal ulcer, abdominal pain, and cancers (Fernandez-Luqueno et al., 2013). Many heavy metal ions, such as Mercury (Hg), Cadmium (Cd), Lead (Pb), Nickel (Ni) and Chromium (Cr) are known to be very toxic or carcinogenic as unlike organic contaminants, heavy metals are not biodegradable and hence, tend to accumulate in living organisms. (Muatuz et al., 2017).

          Medicinal plant contamination with heavy metals is an issue of serious concern. WHO has set the heavy metals limits to ensure the plant’s suitability for medicinal purposes.

Statement of Research Problem

The widespread use of garlic against the corona virus infection and the dearth of information on its potential toxicity justify the need for detailed study in order to investigate the presence of heavy metals in garlic. Hence, this study was designed to analyze the presence of heavy metals and perform a risk assessment in garlic samples obtained from selected locations in Akwa Ibom state and Enugu state.

Aim and Objectives

This research was done to assess the health risks incurred on the masses due to an escalated consumption of garlic in the Covid-19 Era.

The objectives are as follows:

  1. To assess garlic for the presence of heavy metals such as Arsenic, Cadmium, Lead, Mercury and Nickel.
  2. To quantify the heavy metals if present.
  3. To compare the results obtained from both states.

To perform a risk assessment by calculating Estimated Daily Intake, Hazard Quotient and Hazard Index from the results obtained.