**2.4. Classification based on location in plants**

Phenolic compounds that are free in soluble forms in cells are categorised as being in solution while those bound as complexes in the cell wall, as insoluble. Soluble phenolic compounds include low and medium molecular weight phenolics such as simple phenol, flavonoids and tannins. Insoluble phenolics include high molecular weight tannins and phenolic acids. Other insoluble phenolics include those bound to polysaccharides in the cell walls (usually with low molecular weight), and proteins [10].
