New Genera of Flavonols and Flavonol Derivatives As Therapeutic Molecules

Natural products from plants and microorganisms traditionally have provided the pharmaceutical industry with one of the most important sources of lead compounds in the search for new drugs and medicines. The diversity of polyphenol structure is enormous. They are classified into several classes, the most important polyphenol in our food being phenolic acids and flavonoids, which include flavonol as one of subgroups. Flavonols are a group of plant secondary metabolites containing hydroxyl in 3(rd) position of chromone ring of a '6+3' flavonoid ring structure. Several health beneficial activities have been attributed to these naturally occurring plant flavonols, including antioxidative, anticarcinogenic, vasoprotective, anti-inflammatory, neurodegenerative, antidiabetic, antiplatelet activities, among which antioxidative properties remain the main topic investigated in recent years. The main aim of this review is to put forward the pharmacological importance of major flavonols and newly found flavonol derivatives from the last 10 years and their related bioactivity as lead compounds. The bioactivity of these flavonoids depends on structure-activity relationship (SARs), the flavonols being one of the structurally active compounds. Most studies have demonstrated their occurrence and their absorption in humans, but the question remains as to which form is actually absorbed: aglycone, glycosidic or both. The major flavonols such as quercetin, kaempferol, myricetin, rutin, isorhamnetin, and galangin were found to exhibit anticancer activity. These flavonols also have positive effects on major diseases such as cardiovascular disease, type-2 diabetes, and Alzheimer's disease. They are also found to have therapeutic value against osteoporosis, platelet aggregation, and antioxidant activity, the major action of prevention.