Corn

Immature corn shoots accumulate the potent antibiotic substance DIMBOA.

An excerpt from the article 20 facts about corn

DIMBOA (2,4-dihydroxy-7-methoxy-1,4-benzoxazin-3-one) belongs to a group of hydroxamic acids (benzoxazinoids) that serve as natural defenses against a wide range of pests, including insects, pathogenic fungi, and bacteria. As corn matures, DIMBOA levels decrease.

DIMBOA is also found in wheat.