INTRODUCTION:

Towards the end of December 2019, in Wuhan, China, a novel RNA virus responsible for the human coronavirus, identified as COVID-19 and officially recognized as SARS-CoV-2 (Severe Acute Respiratory Syndrome Coronavirus-2) by the International Committee on Taxonomy of Viruses (ICTV), was discovered. Within a few weeks of its discovery, the virus had rapidly spread, leading to a global pandemic.

Target of Coronavirus:

Coronaviruses belong to the Coronaviridae family in the Nidovirales order. They are characterized by crown-like spikes on their outer surface, hence the name coronavirus. These viruses are minute in size (65-125 nm in diameter) and contain a single-stranded RNA as their nucleic material, varying in length from 26 to 32 kb. The subgroups of the coronavirus family include alpha (α), beta (β), gamma (γ), and delta (δ) coronaviruses. SARS-CoV-2 fits into the beta coronavirus group. COVID-19 (SARS-CoV-2) is composed of several proteins: a spike protein (S), a membrane glycoprotein (M), a hemagglutinin-esterase dimer (HE), an envelope protein (E), a nucleocapsid protein (N), and an RNA. Spike glycoproteins are composed of two subunits (S1 and S2). Homotrimers of S proteins form the spikes on the viral surface, facilitating attachment to host receptors.

COVID-19 Pandemic in India:

The COVID-19 pandemic in India emerged as part of the global contagion caused by SARS-CoV-2. By 27th March 2022, India reported the second-highest number of confirmed COVID-19 cases (43,019,453) globally and the third-highest number of deaths (521,004). The first case in India was reported in Thrissur, Kerala on 30th January 2020 in students returning from Wuhan, China. By 24th March 2020, the country had recorded a total of 9 deaths and 519 confirmed cases. In response to the escalating threat, the government announced a 21-day nationwide lockdown on 25th March 2020, which was later extended to 31st May 2020 by the National Disaster Management Authority. Due to the lack of a standard treatment regime against COVID-19, various treatment modalities and preventive measures were employed to manage the condition of infected patients. In light of scientific and epidemiological evidence, vaccination was considered the primary focus and was aggressively pursued.^1,2

Herbal Remedies:

Herbs have a long history of use as remedies against a wide range of infections such as the common cold, inflammation, fever, and even herpes. For centuries, herbs such as garlic, ginger, and neem have been used to treat various respiratory infections, including the flu and pneumonia. It is estimated that more than 70% of drugs are formulated from herbs. For instance, Artesunate and other related anti-malaria drugs are produced from artemisinin, a phytochemical extracted from Artemisia annua. Different parts of plants are used to prepare herbal medicines, which have been highly effective in nearly 80% of primary health care cases. Herbal medicines are believed to be more available, affordable, safe, and natural, with fewer side effects compared to synthetic drugs. However, one of the challenges associated with herbs in many countries, including India, is that herbal and natural remedies are often prepared under unhygienic conditions.

India is globally recognized for producing valuable herbal medicines for the treatment of various diseases. Numerous herbal products currently in use for treating global health challenges such as cancer, high blood pressure, stroke, heart diseases, diabetes, and sickle cell anemia have emerged from India. Consequently, the concentration of research scientists in this field has been increasing. During the COVID-19 pandemic, several organizations worldwide, both governmental and private, have been conducting research and formulating herbal remedies from plants and plant products in an effort to find a cure for the disease.³

Objective:

In the face of the COVID-19 pandemic and the initial unavailability of potent vaccines, there has been a tremendous global quest to find cures through herbal medicine as an alternative. This paper aims to review and highlight common herbs touted as preventives and cures against COVID-19, including their vital botanical information and previously associated ailments.

Herbal Remedies for COVID-19: An Overview of Medicinal Plants

Garlic (Allium sativum)

Common Name: Garlic, Lahasun

Scientific Name: Allium sativum

Biological Source: Bulb

Family: Amaryllidaceae

Chemical Constituents: Allicin, allin, flavonoids, saponins

Mechanism of Action: Suppresses SARS-CoV-2 by creating a hydrogen bond between amino acids and the binding site of the virus.

Predicted Targets in COVID-19: The binding site of the virus.

Garlic (Allium sativum) is a species of the genus Allium, widely regarded as a food supplement. Native to Central Asia, garlic is now cultivated worldwide for its numerous medicinal benefits. It is used as a condiment and traditional medicine to treat various diseases. The main producers of garlic are India, South Korea, Spain, China, and the United States. Garlic has been extensively investigated and used for centuries to combat infectious diseases, thanks to its phytochemical constituents such as sulfur compounds, high trace mineral content, and enzymes. Allicin, the dominant sulfur compound in garlic, is present at 10 mg/g in fresh garlic or 30 mg/g dry. Fresh crushed garlic combined with honey can enhance immunity and exhibits antimicrobial and antiviral activity.

Liquorice (Glycyrrhiza glabra)

Common Name: Mulhethi, Yashtimadhu, Liquorice

Scientific Name: Glycyrrhiza glabra L.

Biological Source: Peeled and unpeeled roots, stolons, and stems

Family: Fabaceae

Chemical Constituents: Arabinogalactan protein

Mechanism of Action: Reduces the expression of TMPRSS2 and ACE2.

Predicted Targets in COVID-19: Mononuclear cell factor and pro-inflammatory cytokines.

Liquorice (Glycyrrhiza glabra) is a medicinal herb used to cure various chronic infections since ancient times. The dried and crushed roots of liquorice are boiled to prepare a root extract, which can be dried into a dark powder. This powder can be taken orally to treat chronic diseases. Glycyrrhizin, a saponin present in the root extract, shows antimicrobial, immunomodulatory, and antiviral activity.

Neem (Azadirachta indica)

Common Name: Neem, Neemb

Scientific Name: Azadirachta indica

Biological Source: Fresh or dried leaves and seeds

Family: Meliaceae

Chemical Constituents: Azadirachtin, azadirone

Mechanism of Action: Binding efficacy with main proteases of SARS-CoV-2.

Predicted Targets in COVID-19: Inhibitory effect on main proteases of SARS-CoV-2.

Neem (Azadirachta indica) is a tropical evergreen tree native to Asia and widely cultivated in Southeast Asia and West Africa. In India, neem is used in various forms: twigs for teeth whitening, leaves for salads and skin remedies, and juice for blood tonics. Neem's leaves possess antiviral properties and are used to treat various ailments including malaria, fever, anemia, and skin infections. Research has shown that neem leaves contain quercetin and nimbosterol, which have antiseptic, antifungal, and antibacterial properties.^4,5,6,7

Lemon (Citrus limon)

Common Name: Neembu, Lemon

Scientific Name: Citrus limon

Biological Source: Juice of citrus fruit

Family: Rutaceae

Chemical Constituents: Citric acid, diosmin, hesperidin, limocitrin, phenolic acids

Mechanism of Action: Affinity to COVID-19 helicase and spike proteins.

Predicted Targets in COVID-19: Inhibits the main protease of SARS-CoV-2.

Lemon (Citrus limon) is a small evergreen flowering plant species with about 1300 species. The ripe fruits are ovoid, globose, or yellow. Lemons have various medicinal properties, including anticancer and antibacterial activities. Lemon juice, rich in vitamin C, is used to lighten the skin, stimulate the liver, control nausea, and relieve heartburns and irritable bowel syndrome. It is also used to treat urinary tract infections, gall bladder, and kidney stones.

Lemongrass (Cymbopogon citratus)

Common Name: Lemongrass

Scientific Name: Cymbopogon citratus

Biological Source: Aerial leaf

Family: Poaceae

Chemical Constituents: Citral, geraniol, linalool, limonene, dipentene, triacontene, tricontanol, terpenolene, αβ pinene

Mechanism of Action: LEO can weaken the HIV transcription and virus reactivation by interfering with the Tat/TAR-RNA complex.

Predicted Targets in COVID-19: Inhibit the SARS-CoV-2 infection pathway.

Lemongrass (Cymbopogon citratus) belongs to the grass family and is native to Asia, Africa, Australia, and tropical islands. It is used in poultry and fish feeds and as an ingredient in soups, teas, and curries. Lemongrass essential oil (LEO) may inhibit the SARS-CoV-2 infection pathway. Lemongrass is known for its antioxidant properties and is used to treat body pains, inflammations, fever, high blood sugar, cholesterol levels, and to regulate menstrual flow. It is also used in stress, anxiety, and depression management through aromatherapy.

Ginger (Zingiber officinale)

Common Name: Ginger, Adrak

Scientific Name: Zingiber officinale

Biological Source: Rhizome

Family: Zingiberaceae

Chemical Constituents: Gingerdiones, gingerdiols, 6-gingerol, 10-gingerol

Mechanism of Action: Affinity for SARS-CoV-2 S-spike protein as well as papain-like protease (PLpro).

Ginger (Zingiber officinale) is a subtropical and tropical perennial herb with a long history of use in cuisine and medicine. Ginger is attributed with therapeutic properties against infections and health conditions such as cancer, cold, fever, coughs, nausea, Alzheimer's disease, and inflammation. Its efficacy is believed to be due to phytochemicals such as terpenoids and phenylpropanoid-polyketides._8,9,10,11

Turmeric (Curcuma longa)

Common Name: Turmeric, Haldi

Scientific Name: Curcuma longa

Biological Source: Rhizome

Family: Zingiberaceae

Chemical Constituents: Curcumin-A, Curcumin-B, curcuminoids

Mechanism of Action: Acts as an adjuvant with hydroxychloroquine for breaking the structural uniformity of the virus.

Predicted Targets in COVID-19: Binding proteins of COVID-19.

Description:

Turmeric (Curcuma longa) is a tropical perennial herb with a history of use in cuisine and medicine. Turmeric has therapeutic properties against a wide range of infections and health conditions such as cancer, cold, fever, coughs, nausea, Alzheimer's disease, and inflammation. Its efficacy is attributed to phytochemicals like terpenoids and curcuminoids.^12,13,14,15

CONCLUSION:

In the context of the COVID-19 pandemic, various herbs such as garlic, liquorice, neem, lemon, lemongrass, ginger, and turmeric have been investigated for their potential antiviral properties. These plants offer promising avenues for alternative treatments, leveraging their bioactive compounds to target different mechanisms of SARS-CoV-2. Continued research and clinical trials are necessary to fully understand and harness their potential in combating COVID-19.^16,17,18

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Received on 12.08.2024 Revised on 01.10.2024

Accepted on 06.11.2024 Published on 05.03.2025

Available online from March 11, 2025

Res. J. Pharmacognosy and Phytochem. 2025; 17(1):65-68.

DOI: 10.52711/0975-4385.2025.00011

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