~ 3344 ~ Journal of Pharmacognosy and Phytochemistry 2019; 8(4): 3344-3358 E-ISSN: 2278-4136 P-ISSN: 2349-8234 JPP 2019; 8(4): 3344-3358 Received: 06-05-2019 Accepted: 10-06-2019 Sonali kulasari P.G. Student, Department of Pharmacy, Sardar Bhagwan Singh Post Graduation of Biomedical Sciences and Research, Dehradun, Uttarakhand, India Mamta F Singh Prof., Department of Pharmacy, Sardar Bhagwan Singh Post Graduation of Biomedical Sciences and Research, Balawala, Dehradun, Uttarakhand, India Shradha Bhandari Prof., Department of Pharmacy, Sardar Bhagwan Singh Post Graduation of Biomedical Sciences and Research, Balawala, Dehradun, Uttarakhand, India Correspondence Sonali kulasari P.G. Student, Department of Pharmacy, Sardar Bhagwan Singh Post Graduation of Biomedical Sciences and Research, Dehradun, Uttarakhand, India Polyphenols: Phytochemistry and health benefits Sonali Kulasari, Mamta F Singh and Shradha Bhandari Abstract Phenolic compounds are the phytoconstituents from plants with diverse chemical properties and bioactivities. Since the ancient time polyphenols compounds are widely used in Indian medicine system due to their health benefits. The phenolic compounds are subdivided into five major classes, phenolic acids, flavonoids, tannins, lignans, and coumarins. Phenolic acids are the derivative of esters and glycosides which is associated with flavonoid, alcohols, hydroxy fatty acids, sterols, and glucosides. flavonoids are a group of bioactive compounds which includes flavonols, flavones, flavanones, flavonoid glycosides isoflavones, and anthocyanins. Tannins are the secondary metabolites which have an activity to precipitate protein. Lignans and coumarins are one of the most important groups of plant secondary metabolites. The phenolic compounds show various pharmacological activities such as anti-inflammatory activity (Vanillic acid, and catechin), anti-asthmatic activity (Protocatechuic acids), antidiabetic activity (Cinnamic acid), and cardioprotective activity (Daidzein). This review addresses the introduction of phenolic compounds, their classifications, chemical structure, and pharmacological activities. Keywords: Phytoconstituents, bioactivites, polyphenols, precipitate Introduction Phenolic compounds are the diverse group of phytochemicals which are expanded in the plant kingdom. These are plants secondary metabolites containing an aromatic ring substituted with hydroxyl groups [1] . Additionally, 8,000 phenolic structures have been believed to present in plant kingdom which is categorized according to simple low- molecular weight compounds to large complex tannins and polyphenols [2] . Phenolic compounds are synthesized by two metabolic pathway: the shikimic acid pathway and the acetic pathway. In shikimic acid, pathway phenylpropanoids are formed whereas in acetic acid pathway simple phenols are formed. The junction of this pathway leads to the formation of flavonoids and after the condensation process, non-hydrolysable tannins are formed. Phenolics compounds are present in the bound form with sugars (Glycoside residue) and proteins inside the cell vacuoles. In free form, they are toxic in nature [3] . The biochemist explains that the phenol makes a complex structure with protein by hydrogen bonding. During the isolation process, the phenolic content decreases. Phenols are very sensitive to enzymatic oxidation thus the extraction with boiling alcohol may limit the enzymatic oxidation [4] . The dietary phenolic compounds include flavonoids, phenolic acids, and polyphenols which shows various pharmacological activity Phenolic compounds show various function in plants such as 1. Show the defense mechanism for herbivores and pathogens [5] . 2. Attract pollinators and fruit dispersers [5] . 3. Reduce the growth of nearby competing plants [5] . 4. Involves in plants sensorial properties like color, aroma, taste, and astringency [3] . 5. Responsible for the germinating process of seed after harvesting and growth as well as development and reproduction [3] . Classification The classification of phenolic compounds is determined by a large number of heterogeneous structures which covers the area of simple molecules to higher polymerized compounds [3] . According to the circulation in nature, phenolic compounds are categorized into three classes: 1. Shortly distributed includes simple phenols, pyrocatechol, hydroquinone, resorcinol, and aldehyde derived benzoic acid. 2. Widely distributed includes flavonoids and their derivatives, coumarin and phenolic acids such as benzoic acid and cinnamic acid and their derivatives. 3. Polymers include tannins and lignin [6] .