Immunosuppressive phytochemicals and phytonutrients in plants in Nigeria: a systematic review

Immunosuppressive agents are crucial for managing autoimmune diseases and organ transplants, but synthetic options often cause significant side effects. Nigerian medicinal plants, rich in bioactive compounds, present a promising natural alternative for immune modulation. This systematic review examines the immunosuppressive properties of phytochemicals and phytonutrients from Nigerian plants, focusing on their mechanisms of action and therapeutic potential.

A comprehensive literature search was conducted following PRISMA guidelines across major databases, including PubMed, Scopus, Google Scholar, the Cochrane Library, Web of Science, and AJOL. The search covered studies published between January 2000 and August 2024 using keywords like "immunosuppressive," "phytochemicals," "phytonutrients," and specific Nigerian plants. Studies were included if they investigated the immunosuppressive effects of Nigerian plants through in vitro, in vivo, or clinical methods. Non-immunological studies were excluded. Data extraction and quality assessment were independently performed by two reviewers.

A total of 141 studies were reviewed, identifying several Nigerian plants with notable immunosuppressive effects. Azadirachta indica (neem) demonstrated a strong ability to inhibit T-cell proliferation and cytokine production. Vernonia amygdalina (bitter leaf) and Garcinia kola (bitter kola) were effective in reducing pro-inflammatory cytokines and modulating lymphocyte activity. Other plants, including Ocimum gratissimum (scent leaf), Allium sativum (garlic), and Zingiber officinale (ginger), exhibited promising immunosuppressive properties by regulating cytokine release and immune cell activation. These findings suggest that Nigerian medicinal plants offer diverse and effective immunosuppressive agents, working through mechanisms like cytokine inhibition and signaling pathway modulation.

This review highlights the therapeutic potential of Nigerian phytochemicals as immunosuppressive agents, encouraging further research to explore their clinical applications and integration into current treatment frameworks. Future clinical trials are essential to validate their efficacy and safety, with potential uses in autoimmune disease management, inflammatory conditions, and organ transplantation.