Here the original text has the simple past-tense form partook for the past participle. In his editing for the 1837 edition, Joseph Smith corrected the reading in 𝓟 by adding en to the verb, but he probably intended partaken rather than what he actually wrote, partooken.
In one other place, an original “had partook” has been edited to “had partaken”:
Elsewhere the text has only the standard past participial form partaken (three times). For complete discussion, see under past participle in volume 3.
Summary: Restore the original simple past-tense form in the verb phrase “had partook” in 1 Nephi 8:25.