Phenolics and Polyphenolics from Melastomataceae Species

The Melastomataceae family, the seventh largest flowering plants, has been studied in several fronts of natural product chemistry, including terpenoids, simple phenolics, flavonoids, quinones, lignans and their glycosides, as well as a vast range of tannins or polyphenols. This review concerns the phenolic and polyphenolic metabolites described in the literature for several genera of this family, the mode of isolation and purification, and the structure elucidation of these new natural products that has been achieved by extensive spectral analyses, including ESI-MS, (1)H-, (13)C-NMR spectra and two-dimensional experiments, COSY, TOCSY, J-resolved, NOESY, HMQC, DEPT, and HMBC, as well as chemical and enzymatic degradations and the chemotaxonomic meaning. Finally, a general biogenetic pathway map for ellagitannins is proposed on the bases of the most plausible free radical C-O oxidative coupling.