Antidepressant effects of 70% ethanolic extract of Lonicerae japonicae flos and it contained chlorogenic acid via upregulation of BDNF-TrkB pathway in the hippocampus of mice

Lonicera japonica flos (LJF) is a common clinical herb with outstanding medicinal and nutritional value. This study aimed to evaluate the antidepressant effects of LJF's active extract and compound chlorogenic acid (CGA) around BDNF-TrkB pathway. The results showed that LJF extracts and CGA had significant antidepressant effects, and the antidepressant effects of different extracts of LJF was highly positively correlated with the content of CGA (FST, r = 0.998; TST, r = 0.934). Moreover, LJF-70% ethanolic extract and CGA improved CUMS induced depressive behavior, upregulated protein expression levels of BDNF and p-TrkB in the hippocampus, restored the damage of hippocampal neurons, and protect liver from damage. In summary, this study demonstrated for the first time that LJF-70% ethanolic extract was the active extract of LJF antidepressant and CGA was its active antidepressant compound, and the antidepressant mechanism mainly involved the upregulation of BDNF-TrkB signaling pathway in the hippocampus of mice.