Therapeutic Potentials of Secoiridoids from the Fruits of Ligustrum lucidum Aiton against Inflammation-Related Skin Diseases.

Ligustrum lucidum Aiton is a flowering plant of the Oleaceae family, and its fruits have been traditionally used for skin nourishment and the treatment of skin diseases. However, the anti-inflammatory constituents for skin disease are not well-characterized. Phytochemical investigation of L. lucidum fruits resulted in the isolation of a new secoiridoid, secoligulene ( 1 ), together with ( E )-3-(1-oxobut-2-en-2-yl)pentanedioic acid ( 2 ) and trans -( E )-3-(1-oxobut-2-en-2-yl)glutaric acid ( 3 ). Secoligulene ( 1 ) displayed the potent inhibitory effect on NO production with an IC 50 value of 12.0 μg/mL. Secoligulene ( 1 ) also downregulated mRNA transcriptional levels of pro-inflammatory cytokines such as IL-1 α, IL-1β, IL-6 and COX-2 in LPS-stimulated RAW264.7 cells. Further investigation showed that secoligulene ( 1 ) inhibited the phosphorylation of IκB and JNK activated by LPS. In addition, secoligulene ( 1 ) downregulated the expression of chemokines such as CXCL8 and CCL20 in the TNF-α/IL-17/IFN-γ induced HaCaT psoriasis model. Taken together, these findings support the beneficial effects of L. lucidum and its constituents on inflammation-related skin diseases and can be further developed as therapeutic treatments for related diseases.