Rich in rosmarinic acid, a powerful antioxidant, rosemary leaves have been shown to increase blood flow to the brain, giving credence to the herb’s reputation as a memory tonic. (In ancient Greece, students used to put rosemary in their hair when studying.) Native to the Mediterranean but thriving in any warm climate, the herb contains anti-inflammatory and immune-boosting compounds and is a good source of iron, calcium, and potassium.