Sentence:  Proanthocyanidins are included in the <WSD>pycnogenols</WSD>, a plant polyphenol chemical group, whose physical, chemical and biological properties have been studied in numerous works (see more especially J. Masquelier, J. Michaud, J. Laparra, and M. C. Dumon, Internat. J. Vit. Nutr. Res. 1979, 49, 307-311). 
Meaning of the word marked with <WSD> tags:  Any of a group of flavonoids extracted from the bark of pine trees, especially proanthocyanidins.