Beyond vitamin C: the diverse, complex health-promoting properties of citrus fruits

Humans discovered citrus fruit centuries ago and today consider citrus among the most‑healthy foods in the human diet. In addition to the carbohydrates, citrus fruit contains various health beneficial components such as carotenoids, vitamin C, and polyphenols, including flavonoids and anthocyanins. Additionally, citrus fruits contain biologically active compounds such as mono- and triterpenoids, coumarins, alkaloids, phytosterols, pectin, and polymethoxy flavones. Whole fruit contains these secondary metabolites at microgram to nanogram levels and processed juice has lower levels. However, despite their lower concentrations, these compounds can prevent several acute and chronic diseases, possibly via synergistic or cumulative effects with regular consumption. Accumulating evidence shows that citrus consumption reduces the risk of cardiovascular disease and obesity, and can promote weight loss and prevent infections. During the last three decades, further research has revealed additional benefits of citrus-derived compounds, such as inhibition of tumor growth due to their anti-inflammatory and anti-angiogenic properties. Interestingly, compounds found in non-edible parts of the citrus fruit, such as peels and pulp, have stronger activity against different cancers. Certain compounds, including obacunone, apigenin, synephrine, hesperidin, and pectin have shown activity parallel to existing natural cytotoxic compounds. Our group has conducted extensive research in chemical fingerprinting of different citrus fruits, isolating and separating active molecules, and exploring their health benefits using molecular, animal, and human studies. In the current article, we discuss characterization and isolation of key phytochemicals and explore the major biological benefits of using these molecules, ranging from cellular to systemic effects.