Quercetin, a low-molecular-weight flavonoid, is a potent antioxidant with five functional hydroxyl groups that capture free radicals. It has various pharmacological properties, including carcinostatic, antiviral, antihypertensive, and anti-inflammatory effects. Quercetin is widely distributed in plants and fruits, with significant sources such as capers, tea, tomatoes, and grapes. Its aglycone form is found in onions, while glycosylated forms are more common in dietary intake. Quercetin's bioavailability is relatively low due to its poor water solubility and chemical stability. However, it can be absorbed through active transport mechanisms and undergo metabolic transformations in the gastrointestinal tract and liver. Quercetin's pharmacological properties include its ability to scavenge reactive oxygen species, protect low-density lipoprotein from oxidation, inhibit angiogenesis, and modulate signaling pathways involved in cancer. It also exhibits antimicrobial and antiviral activities, hepatoprotective effects, and potential therapeutic benefits for conditions like Alzheimer's disease, cardiovascular diseases, diabetes, arthritis, and cancer. Synergistic effects with other drugs have been observed in treating breast, prostate, and leukemia cancers. Quercetin targets cell cycle and apoptosis pathways, influencing proteins like p53, p21, and cyclin B, and inducing apoptosis through various mechanisms.Quercetin, a low-molecular-weight flavonoid, is a potent antioxidant with five functional hydroxyl groups that capture free radicals. It has various pharmacological properties, including carcinostatic, antiviral, antihypertensive, and anti-inflammatory effects. Quercetin is widely distributed in plants and fruits, with significant sources such as capers, tea, tomatoes, and grapes. Its aglycone form is found in onions, while glycosylated forms are more common in dietary intake. Quercetin's bioavailability is relatively low due to its poor water solubility and chemical stability. However, it can be absorbed through active transport mechanisms and undergo metabolic transformations in the gastrointestinal tract and liver. Quercetin's pharmacological properties include its ability to scavenge reactive oxygen species, protect low-density lipoprotein from oxidation, inhibit angiogenesis, and modulate signaling pathways involved in cancer. It also exhibits antimicrobial and antiviral activities, hepatoprotective effects, and potential therapeutic benefits for conditions like Alzheimer's disease, cardiovascular diseases, diabetes, arthritis, and cancer. Synergistic effects with other drugs have been observed in treating breast, prostate, and leukemia cancers. Quercetin targets cell cycle and apoptosis pathways, influencing proteins like p53, p21, and cyclin B, and inducing apoptosis through various mechanisms.