Protocatechuic acid with anti-autoimmune orchitis activities from lychee seed and its mechanisms on the TLR/NF-κB...

Lychee Seed (LS), a traditional Chinese medicinal material, has been historically used in China for the management of conditions such as testicular swelling and pain and hernia. Modern phytochemical studies have revealed that it is rich in flavonoids and procyanidins. Recent investigations have indicated its potential in mitigating autoimmune orchitis (AO); however, the precise mechanisms underlying its anti-AO effects remain to be fully elucidated.

This study aimed to clarify the therapeutic potential of LS for autoimmune orchitis, identify its bioactive components, and elucidate the underlying mechanisms through a comprehensive methodology that combined activity-guided screening, network pharmacology, molecular docking, and experimental validation both in vitro and in vivo.

LS was isolated and purified using a combination of chromatographic methods, including silica gel, D101 macroporous resin, MCI, ODS, Sephadex LH-20, and semi-preparative HPLC. Structural identification of the obtained compounds was performed through analysis of their physicochemical properties and spectroscopic data. Through activity-guided fractionation of the active fractions from LS, the compounds were isolated and identified. The anti-inflammatory activities of these compounds were evaluated by measuring their half-maximal inhibitory concentration (IC₅₀) on nitric oxide (NO) production in lipopolysaccharide (LPS) induced RAW264.7 macrophages. Furthermore, to investigate the mechanisms underlying their anti-orchitis effects, an integrated approach combining network pharmacology, molecular docking, and in vivo experiments was employed.

The study investigated the therapeutic effects of LS extract on testiculitis in mice. Preliminary pharmacological screening demonstrated that both the ethanol extract and the ethyl acetate fraction of LS significantly ameliorated inflammatory levels and histopathological changes in model animals. A total of twenty-four compounds, predominantly flavonoids and phenolic acids, were isolated from LS. Among these, one previously undescribed jasmonate derivative (compound 9) was identified. Cellular screening assays revealed that compound 23 exhibited notable anti-inflammatory activity. In vivo experiments further demonstrated that compound 23 attenuated the progression of autoimmune orchitis by modulating the TLR2/3/4-NF-κB signaling pathway, resulting in reduced inflammatory cytokine secretion, improved sperm parameters, and restored testosterone levels.

These findings suggest that LS attenuates testicular inflammation and improves spermatogenic function by modulating the TLR2/3/4-NF-κB pathway, ultimately leading to restored testosterone levels and alleviation of testicular swelling and pain.