Spices & Herbs as Potential Antiviral Agents and Immunity Boosters

In the current pandemic scenario, the best choices against COVID‐19 infection are precautions and boosting immunity. Recent studies support the fact that certain spices and herbs may play a significant role against SARS‐CoV‐2 (COVID‐19) and other viral infections. In India, people use spices and herbs from ancient times due to their taste, antiviral, antimicrobial, antioxidant, and immunity‐boosting properties. This article highlights the antiviral potential of some common spices and herbs.

Turmeric (Curcuma longa)

Turmeric, commonly known as Haldi, belongs to the family Zingiberaceae contains curcumin, a natural polyphenol, which has antiviral activity against different viruses, including hepatitis, influenza, herpes simplex, dengue, chikungunya, SARS coronavirus, and human immunodeficiency virus (HIV). Turmeric inhibits the growth and replication of the virus by targeting various cellular pathways, further making it an ideal candidate as an antiviral agent. Turmeric's antiviral activities can be attributed to its ability to regulate multiple molecular targets that contribute to various cellular events, such as transcription regulation and the activation of cellular signaling pathways. Studies show that turmeric binds and inhibits the target receptors, including SARS‐CoV‐2 protease, spike glycoprotein Receptor-Binding Domain Protein (RBD), and peptidase domain of Angiotensin-Converting Enzyme 2 (PD‐ACE2), which are involved in virus infection.

Ginger (Zingiber officinale)

Ginger, known as Sunthi in Ayurveda, belongs to the Zingiberaceae family. Studies prove that ginger and its bioactive compounds show antiviral activity against Influenza, Herpes, Chikungunya, SARS‐CoV‐2, and Human respiratory virus. Ginger inhibits hepatitis C virus replication monitored by amplifying viral RNA segments. Studies show that the bioactive compounds of ginger block the spike (S) protein from binding to the angiotensin‐converting enzyme 2 (ACE2) receptor or act as an inhibitor for Main Protease (MPro) protein. The S protein is responsible for SARS‐CoV‐2 entry during the infection, which binds with the angiotensin‐converting enzyme 2 (ACE2) receptor from the host cell to generate an appropriate environment for viral replication. Main Protease (MPro) is accountable for processing the poly‐proteins pp1a and pp1ab during viral replication.

Cinnamon (Cinnamomum cassia)

Cinnamon, commonly known as Dalchini, belongs to the Lauraceae family. Cinnamon is widely used all around the world as a daily condiment. The bark of cinnamon contains compounds such as cinnamaldehyde and eugenol, which have antiviral and antibacterial effects. Several scientific studies have proven cinnamon's antimicrobial, antiviral, antifungal, antioxidant, antihypertensive, antidiabetic, antitumour, gastroprotective, and immunomodulatory effects. Regular use of cinnamon averts throat infections. Studies show that the extract of cinnamon is effective against the herpes simplex virus (HSV), and it reduces the viral titre of HSV by preventing viral attachment to cells. According to another study, cinnamon increases the phagocytic index, serum immunoglobulin levels, and antibody titre by increasing both cell‐mediated and humoral immunity.

Clove (Syzygium aromaticum)

Clove, commonly known as Lavang or Laung, belongs to the family Myrtaceae. Clove is well known for its antiemetic and carminative properties. Clove is used in the food industry for increasing the shelf‐life of food due to its antimicrobial activities. The main bioactive component of clove, eugenol, exhibits broad antimicrobial activities against Gram‐positive, Gram‐negative, and acid-fast bacteria and fungi. Eugenie, a compound isolated from the extract of cloves, works against the herpes virus. The inhibitory action of eugeniin and eugenol is on the viral DNA synthesis and viral replication, thus reducing infection.

Black pepper (Piper nigrum)

Black pepper, commonly known as Kali Mirch, is a member of the family Piperaceae. It has a pungent smell and is known as the king of spices. It contains alkaloid piperine, which possesses anti‐inflammatory, antioxidant, antipyretic, antitumour, antiasthmatic, analgesic, and antimicrobial properties. Studies show the antiviral activity of Black pepper against vesicular stomatitis virus (an enteric virus) and influenza virus. Piperine inhibits methyltransferase activity of Dengue virus and VP35 interferon inhibitory domain of Ebola virus. Recent studies show that the bioactive compounds from black pepper are active against COVID‐19, which can be further used for its treatment.

Basil (Ocimum basilicum)

Basil, commonly known as Sweet basil, is a popular medicinal herb of the Lamiaceae family. The essential oils of basil possess antimicrobial activities against a wide range of bacteria, fungi, and parasites. Different basil compounds are used to treat viral, respiratory, and hepatic infections. Studies show that the basil leaf extract and seed oil increase T‐helper and natural killer cells, lymphocyte count, phagocytic activity, neutrophil count, and antibody titre, thus enhancing immunity. Basil contains ursolic acid that inhibits viral infections of the herpes simplex virus (HSV) and human immunodeficiency virus (HIV). Phytochemical compounds of basil show inhibition of the main protease of the SARS‐CoV‐2 virus.

Garlic (Allium sativum)

Garlic, commonly known as Lahsun, belongs to the family Liliaceae. It has long been used to improve the taste of food and also helps overcome indigestion. Garlic has anthelmintic, anti‐inflammatory, antioxidant, and antifungal properties. Allicin (diallyl‐dithiosulfinate), found in garlic, shows antiviral activity against the influenza virus. Garlic also shows activity against infectious bronchitis virus (IBV‐a coronavirus), inhibiting the virus penetration and proliferation.

Neem (Azadirachta indica)

Neem is a fast‐growing evergreen tree belonging to the family Meliaceae. Neem has been used in traditional medicine for ages as all parts of neem, such as seeds, roots, leaves, flowers, and bark, are helpful against various diseases. They show insecticidal, antimicrobial, larvicidal, antimalarial, antibacterial, antiviral, and spermicidal effects. Due to its extraordinary properties, neem has been declared as the tree of the 21st century under the United Nations Environment Programme. Neem leaves possess a compound hyperoside that shows antiviral activity against influenza. Neem inhibits the SARS‐CoV‐2 virus by binding to the spike glycoprotein, preventing viral attachment and replication. Neem leaves show a high binding affinity against COVID‐19 main protease protein, the critical protein for viral replication. Another study indicates that the ligands of neem interact and inhibit the residues of spike protease or protease of SARS‐CoV‐2.

Guduchi (Tinospora cordifolia)

Guduchi, commonly called giloy, is a member of the family of Menispermaceae. It is helpful in several diseases such as jaundice, urinary disorder, skin diseases, diabetes, anaemia, inflammation, and allergic condition. Guduchi is also used to improve the immune system and the body's resistance to infections. Guduchi shows antiviral activity against the herpes simplex virus, and it also inhibits the main protease of SARS‐CoV‐2. Giloy shows high binding efficacy against SARS‐CoV‐2 target surface glycoprotein (6VSB), receptor‐binding domain (6M0J), RNA dependent RNA polymerase (6M71), and main protease (6Y84) that are involved in virus attachment and replication.