Are polyhydroquinones considered to be polyphenols?
The WBBSH definition states that polyphenols are defined as:


generally moderately water-soluble compounds
with molecular weight of 500–4000 Da
with >12 phenolic hydroxyl groups
with 5–7 aromatic rings per 1000 Da


This is the most widely accepted definition. However, due to the increase in research, there is a proposed Quideau definition stating

“The term "polyphenol" should be used to define compounds exclusively derived from the shikimate/phenylpropanoid and/or the polyketide pathway, featuring more than one phenolic unit and deprived of nitrogen-based functions.”

However, this is not an official definition (yet)