Ab initio molecular orbital calculations are performed for 15 polyphenols. Highest occupied molecular orbitals (HOMO) at optimized structures are obtained. Electron densities of HOMO on 16 atoms (15 carbons and one oxygen) of molecular framework of flavonoid are used to perform principal component analysis. Plot of the first and the second principal component scores indicates classification of 15 polyphenols into three major groups. The first group includes epigallocatechin and naringenin. The second group consists of 7 polyphenols. The third one consists of 6 polyphenols.