PMFs exclusively exist in citrus peels. From both in vitro and in vivo testing, they have been found to have multifunctional biological benefits including anti-tumor activity, inhibition of inflammation, and prevention of metabolic syndrome such as hyperglycemia and hyperlipidemia, etc. The PMFs are particularly known for their potent efficacious anti-cancer property. Polyhydroxyflavonoids (PHFs) such as hesperidin are abundant in citrus fruits. The citrus PHFs (flavonoids) are well known for their biological activities against oxidation, inflammation, and carcinogenesis, etc. However, what are the biological properties of the poly-molecular combination of PMFs and PHFs? We found that the natural extracts from citrus peels, mainly mixture of PMFs and PHFs, are very efficacious in treating human cancers, including lung cancer, liver cancer, prostate cancer, leukemia, stomach cancer, etc. This presentation will describe our methodology and findings from the application of a citrus peel extract, currently marketed as cosmetic use, on human cancers as well as the correlation between its content of PMFs and PHFs measured in our research laboratory and the effective dosage to warrant efficacious effects in treating human cancers.