Phytoimmunomodulators: A review of natural modulators for complex immune system

Abstract

In the past few decades, the medicinal properties of plants and their effects on the human immune system are being studied extensively. Plants are an incredible source of traditional medicines that help cure various diseases, including altered immune mechanisms and are economical and benign compared to allopathic medicines. Reported data in written documents such as Traditional Chinese medicine, Indian Ayurvedic medicine support the supplementation of botanicals for immune defense reactions in the body and can lead to safe and effective immunity responses. Additionally, some botanicals are well-identified as magical herbal remedies because they act upon the pathogen directly and help boost the immunity of the host. Chemical compounds, also known as phytochemicals, obtained from these botanicals looked promising due to their effects on the human immune system by modulating the lymphocytes which subsequently reduce the chances of getting infected. This paper summarises most documented phytochemicals and how they act on the immune system, their properties and possible mechanisms, screening conventions, formulation guidelines, comparison with synthetic immunity-enhancers, marketed immunity-boosting products, and immune-booster role in the ongoing ghastly corona virus wave. However, it focuses mainly on plant metabolites as immunomodulators. In addition, it also sheds light on the current advancements and future possibilities in this field. From this thorough study, it can be stated that the plant-based secondary metabolites contribute significantly to immunity building and could prove to be valuable medicaments for the design and development of novel immunomodulators even for a pandemic like COVID-19.

Keywords: Ayurveda; COVID-19; Immunomodulators; Phytoimmunomodulators; Secondary metabolites; Traditional Chinese medicine.

Fig. 1

Immune system overview: Innate immunity and adaptive immunity [3].

Fig. 2

Classified immune modulators with the mechanism of action [3].

Fig. 3

Schematic molecular mechanisms of resveratrol with their targets [19].

Fig. 4

Curcumin: potential mechanisms by which it may be effective against COVID-19 [23].

Fig. 5

Luteolin-targeted pathways involved in inflammatory signaling [34].

Fig. 6

Putative chondroprotective mechanism of berberine via innate immunity [38].

Fig. 7

Pathway: Molecular targets of Artemisia in cancer cells [46].

Fig. 8

Mechanism of blockage of lung cancer progression [53].

Fig. 9

Neuroprotective effect of acetyl-11-keto-β-boswellic acid [62].

Fig. 10

Various potent activities of lupeol [71].

Fig. 11

Eugenol showed antioxidative activity [83].

Fig. 12

A proposed molecular pathway of immunomodulatory effect of Allium staivum [103].