Turmeric (Curcuma longa)

Traditional Indications

Turmeric is anti-inflammatory, antioxidant, anti-hyperproliferative, cholagogue, depurative, diuretic, fumitory, haemostatic, hepatoprotective, stomachic, tonic, vulnerary. Turmeric has been used for many conditions in traditional medicine in India, Pakistan and Bangladesh to alleviate asthma and coughs. Many of its traditional uses are supported by scientific evidence. In Ayurvedic medicine, Turmeric to used reduce inflammation. Turmeric is also regarded as a 'rasayana' herb, which is a branch of Ayurvedic medicine and is used to counteract ageing processes. In Unani medicine, turmeric has been used for conditions such as liver obstruction and jaundice and has been applied externally for ulcers and inflammation. Roasted turmeric has been used as an ingredient of a preparation used to treat dysentery. Turmeric has also been used in tooth powder or paste. A hot water extract of the dried rhizome taken orally was reputed to slow lactation, regulate fat metabolism, help symptoms of diabetes, diarrhoea and liver diseases, and as a tonic calm the stomach. The fresh juice taken regularly on an empty stomach has been used to prevent stomach disorders (1)

In Traditional Chinese Medicine (TCM), turmeric is known as Jiang Huang. Jiang Huang is said to be acrid, bitter, warm and to enter the Spleen and Liver channels. Its main actions are to breaks up Blood stasis and moves Qi and unblocks the channels and alleviate pain (2).

Pharmacognosy

The polyphenol curcumin, a major yellow pigment and phytochemical turmeric, has been shown to possess anti-inflammatory and anti-cancer activities. Curcuma longa has been traditionally used in Asian countries as a medical herb due to its antioxidant, anti-inflammatory, antimutagenic, antimicrobial and anticancer. Curcumin, the main active constituent of turmeric induces apoptosis (programmed cell death) (3-6).
Curcumin has been verified as an anti-cancer compound via multiple molecular targets. Its effective mechanisms include cell cycle arrest, inducing apoptosis, suppressing oncogenes, and enhancing tumour suppressor genes. Curcumin inhibits angiogenesis via its ability to inhibit receptor tyrosine kinase (RTK) pathways (7).

Evidence supports the regulation of COX and LOX enzymes by curcumin as the key mechanism for its beneficial effects in preventing various inflammatory diseases (8). Curcumin inhibits NF-κβ. The nuclear factor NF-κB pathway has long been considered a prototypical proinflammatory signalling pathway, largely based on the role of NF-κB in the expression of proinflammatory genes including cytokines, chemokines, and adhesion molecules. NF-κB has long been considered the “holy grail” as a target for new anti-inflammatory drugs (9). Curcumin inhibits key pro-inflammatory cytokines, IL-1, IL-6 & TNF-α. Suppression of cytokine release correlates with clinical diseases where a cytokine storm plays a significant role in mortality such as pandemic flu (10).

The immune-stimulatory & anti-inflammatory activities of Curcuma are in part contributed to its ability to increase Interferon (IFN) (11). Interferons (IFNs) are a group of signalling proteins made and released by host cells in response to the presence of viruses. IFNs are known as cytokines, molecules used for communication between cells to trigger the protective defences of the immune system that help eradicate pathogens. Interferons "interfere" with viral replication: they activate immune cells, such as natural killer cells and macrophages; they increase host defences by up-regulating antigen presentation by virtue of increasing the expression of major histocompatibility complex (MHC) antigens. In a study investigating curcuma longa found that the immune-stimulatory and anti-inflammatory activities are due to curcumin potent inhibitory effect towards release of PGE2 and IL-12 levels (12).

The diarylheptanoid curcumin inhibits Phase I while inducing Phase II (13, 14). Curcumin restores depleted glutathione (GSH) to assist glutathione conjugation (15). Curcumin induces nuclear factor-erythroid-2-related factor 2 (Nrf2). Nrf2 is a leucine zipper (bZIP) protein that regulates expression of antioxidant proteins thereby protecting against oxidative damage triggered by injury & inflammation (16). Phase-II enzymes are regulated by Nrf2 which is involved in detoxification of AFB1. Aflatoxins B1 are genotoxic & carcinogenic compounds. C P450 enzymes are responsible for AFB1 bioactivation. Aflatoxins B1 (AFB1) are contaminants of improperly stored foods; they are potent genotoxic and carcinogenic compounds. Curcumin prevents AFB1-induced liver injury by modulating Phase I & Phase II enzymes (13).

A systematic review of clinical trials on the effectiveness of curcumin on outcomes of hospitalised COVID-19 patients on common symptoms, duration of hospitalization and deaths. In addition, all of these studies showed that the intervention led to amelioration of cytokine storm effects thought to be a driving force in severe COVID-19 cases. This was seen as a significant (p < 0.05) decrease in proinflammatory cytokines such as Interleukin (IL)1β and IL6, with a concomitant significant (p < 0.05) increase in anti-inflammatory cytokines, including IL-10, IL-35 and transforming growth factor alpha (TGF-α) (17).

A recent study published in Computers in Biology and Medicine demonstrated that the phytochemical curcumin is a potent therapeutic prospect against the severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) Omicron variant. Curcumin (among seven phytochemicals), was found to have the most substantial inhibitory potential with Omicron S protein and to could the Omicron S- human ACE2 (hACE2) complex and SARS-CoV-2 main protease [Mpro also called 3C-like proteinase (3CLpro)]. Mpro/3CLpro plays a crucial role in SARS-CoV-2 replication (18). Curcumin, targets TLR4, which regulates trained immunity (19). Curcumin modulates the TLR4/NF-κB pathway by regulating the expression of proinflammatory miRNAs (20).

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