Fractionation and identification of ocular protective compounds from Kochiae Fructus against oxidative damage in retinal pigment epithelium cells.

Ethnopharmacological Relevance: Kochiae Fructus, the ripe fruit of Kochia scoparia, is a traditional Chinese medicine commonly used to treat eye discomforts and vision problems. Although Kochiae Fructus is mentioned in many classical Chinese medical texts, its protective effects and the roles of its active phytochemicals in eye treatment still lack scientific exploration.

Aim Of The Study: This study aimed to clarify the protective effects and identify the active fractions and compounds of Kochiae Fructus against oxidative stress-induced retinal pigment epithelium (RPE) cell death.

Materials And Methods: Liquid-liquid partitioning was employed to prepare active fractions. Silica gel, RP-18, and Sephadex™ LH-20 gels were used as stationary phases to purify the compounds through column chromatography. Cell models were established by treating ARPE-19 (RPE cell line) with hydrogen peroxide (H₂O₂) and tert-butyl hydroperoxide (TBHP), respectively.

Results: The methanol aqueous fraction from ethyl acetate-soluble extract (KSEM) alleviated oxidant-induced RPE cell death in a dose-dependent manner and activated the Nrf2/HO-1 pathway, a critical defense mechanism against oxidative damage. The isolated flavonols in fraction KSEM, hyperoside, quercetin, and kaempferol, reduced oxidant-induced cell mortality, with quercetin showing the strongest effect. Moreover, combination treatment revealed that hyperoside and kaempferol synergistically enhanced the protective effects of quercetin, making the combined treatment more efficient than quercetin alone.

Conclusions: The protective effects of Kochiae Fructus against oxidative damage in RPE cell was validated with the KSEM fraction. The compound quercetin was identified as the important contributor. However, the synergistic effect of the hyperoside, quercetin, and kaempferol mixture may play a dominant role in the protective action of Kochiae Fructus. Overall, these findings highlight the potential of Kochiae Fructus and its flavonol mixture as a basis for developing treatments targeting ocular diseases associated with oxidative damage in retina.