The Henbane (Hyoscyamus niger) is placed by Ethel Voynich/Theodore Petersen on fol. 31r of the Voynich manuscript and I agree it is a valid possibility. However, I will move it one page to fol.31v because of the shape of the fruits and their position compared to the leaves. It is not a perfect match, but I will leave it there for now. Henbane was part of medieval anesthetics and was used to relieve tooth pain.
Coincidentally the leaf pattern on fol. 31v reminds of the picture of medieval dental scrubbers from 1531 edition of Chirurgia Argellata cum Albucasis, National Library of Medicine (here). Pietro d'Argelata thought at the University of Bologna and performed the autopsy of Pope Alexander V (Peter of Candia) on May 3rd, 1410. Argelata died in 1423, but his Chirurgia saw many editions during the following century of printed books.