Polyphenols are secondary plant metabolites found in many fruits, herbs, and vegetables. This review discusses their bioavailability, antioxidant, and anticarcinogenic properties, along with extraction methods. Supercritical fluid extraction is highlighted as an eco-friendly alternative for polyphenol extraction, offering exceptional separation and protection from degradation. Polyphenols protect against reactive oxygen and nitrogen species, UV light, pathogens, and parasites, contributing to various beneficial biological activities. Their high accessibility, low toxicity, and specificity make them promising anticancer agents. However, their low bioavailability and rapid metabolism pose challenges. Nanoformulation and polyphenol mixtures enhance bioavailability and efficacy. Polyphenols can also reduce toxicity when combined with existing drugs. Dietary polyphenols are often in glycosylated forms, affecting their absorption. Extraction methods include conventional and modern techniques like supercritical fluid extraction. Antioxidant activity is assessed using assays like DPPH and ABTS. Polyphenols are found in various foods, with flavonoids being the largest class. Flavonoids, including quercetin, catechins, and isoflavones, have diverse biological activities. Flavonoids exhibit antioxidant and anticarcinogenic effects by scavenging free radicals, regulating signaling pathways, and modulating cell cycle processes. Catechins, such as EGCG, show strong chemopreventive potential, inhibiting cancer growth and inducing apoptosis. Flavonols, flavones, and flavanones also have antioxidant and anticancer properties. Extraction methods and bioavailability are critical factors in polyphenol efficacy. This review highlights the importance of polyphenols in disease prevention and treatment, emphasizing the need for improved extraction and delivery methods to enhance their therapeutic potential.Polyphenols are secondary plant metabolites found in many fruits, herbs, and vegetables. This review discusses their bioavailability, antioxidant, and anticarcinogenic properties, along with extraction methods. Supercritical fluid extraction is highlighted as an eco-friendly alternative for polyphenol extraction, offering exceptional separation and protection from degradation. Polyphenols protect against reactive oxygen and nitrogen species, UV light, pathogens, and parasites, contributing to various beneficial biological activities. Their high accessibility, low toxicity, and specificity make them promising anticancer agents. However, their low bioavailability and rapid metabolism pose challenges. Nanoformulation and polyphenol mixtures enhance bioavailability and efficacy. Polyphenols can also reduce toxicity when combined with existing drugs. Dietary polyphenols are often in glycosylated forms, affecting their absorption. Extraction methods include conventional and modern techniques like supercritical fluid extraction. Antioxidant activity is assessed using assays like DPPH and ABTS. Polyphenols are found in various foods, with flavonoids being the largest class. Flavonoids, including quercetin, catechins, and isoflavones, have diverse biological activities. Flavonoids exhibit antioxidant and anticarcinogenic effects by scavenging free radicals, regulating signaling pathways, and modulating cell cycle processes. Catechins, such as EGCG, show strong chemopreventive potential, inhibiting cancer growth and inducing apoptosis. Flavonols, flavones, and flavanones also have antioxidant and anticancer properties. Extraction methods and bioavailability are critical factors in polyphenol efficacy. This review highlights the importance of polyphenols in disease prevention and treatment, emphasizing the need for improved extraction and delivery methods to enhance their therapeutic potential.