The molecule is a polyprenylbenzoquinone that is 2,3-dimethylbenzoquinone with a polyprenyl side chain at position 5. There are several naturally-occurring plastoquinones with side chains of different length (containing between 6 and 9 isoprene units).
2,3-dimethyl-5-(3-methylbut-2-enyl)cyclohexa-2,5-diene-1,4-dione