Rosmarinic acid suppresses tau phosphorylation and cognitive decline by downregulating the JNK signaling pathway

Rosmarinic acid (RA), a polyphenol in Lamiaceae herbs, is a candidate preventive ingredient against Alzheimer’s disease (AD) due to potent inhibition of amyloid β (Aβ) aggregation, but its effects on tau phosphorylation and cognitive dysfunction were unclear. This study shows that dietary RA inhibits AD hallmarks—Aβ and phosphorylated tau accumulation—and improves cognition in the 3×Tg-AD mouse model. RA intake suppressed hippocampal inflammation and downregulated the JNK signaling pathway that induces tau phosphorylation. RA exerted anti-inflammatory effects in both central and peripheral tissues. Downregulation of hippocampal JNK signaling may underlie the inhibition of pathological progression and cognitive deficits by RA feeding.