best vs high-grade

best is a noun but high-grade is not a noun.

Word	Noun	Adjective	Verb	Adverb
best	Yes	Yes	Yes	Yes
high-grade	No	Yes	No	No

best (noun)	high-grade (noun)
the supreme effort one can make
the person who is most outstanding or excellent; someone who tops all others

best (adjective)	high-grade (adjective)
(superlative of `good') having the most positive qualities	surpassing in quality
(comparative and superlative of `well') wiser or more advantageous and hence advisable

best (verb)	high-grade (verb)
get the better of

best (adverb)	high-grade (adverb)
it would be sensible
in a most excellent way or manner
from a position of superiority or authority