Antioxidant, Antimicrobial, and Anticancer Activity of Basil (Ocimum basilicum)

<b>Background/Objectives:</b> For many years, herbs and spices have been used, due to their aroma and flavor, in the food industry and cuisine. It is also well known that phytochemicals from these plant parts have many health benefits and are used for the prevention and treatment of many human diseases. Basil (with the most representative species <i>Ocimum basilicum</i>) is a perennial herb with a characteristic aroma, containing many bioactive components such as phenolic acids, flavonoids, tannins, saponins, alkaloids, polysaccharides, vitamins, proteins, amino acids, and essential oils, with beneficial effects on human health. The aim of this study is to review the antioxidant, antimicrobial, and anticancer activity of basil, according to recent literature. <b>Methods:</b> A thorough search in the international databases (Scopus, PubMed, Google Scholar, and Web of Sciences) was conducted from January 2015 to October 2025, using characteristic keywords in combinations. <b>Results:</b> Bioactive components of basil show a significant antioxidant activity, as detected by radical scavenging activity (measured by the 2,2-diphenyl-1-picrylhydrazyl (DPPH), 2,2'-azino-bis-(3-ethylbenzothiazoline-6-sulfonic acid (ABTS), ferric reducing antioxidant power (FRAP), oxygen radical absorbance capacity (ORAC) assays), activation of antioxidant enzymes (glutathione peroxidase (GPX), superoxide dismutase (SOD), catalase (CAT)), enhancement of reduced glutathione (GSH) and reduction in malondialdehyde (MDA) and thiobarbituric acid-reactive substance (TBARS) levels, and protection of cells from hydrogen peroxide (H₂O₂)-toxicity. Additionally, inhibition of growth and cell death of many Gram-positive and Gram-negative bacteria strains, maintained by cell membrane damage, inhibition of efflux pumps, as well as inhibition of biofilm formation, anti-protozoan, antifungal, and antiviral activities, have been noticed for basil bioactive components. A synergism with antibiotics has also been reported. Finally, anticancer activity has been reported, according to apoptosis induction, cell cycle arrest, anxiety reduction, and health improvement of cancer patients. <b>Conclusions:</b> Basil bioactive components have been reported for their high antioxidant, antimicrobial, and anticancer properties. However, future studies, especially at the clinical level, are strongly proposed in order to unravel the significant role of basil in human health and the safety of its bioactive components in healthcare usage.