Undulanoids A-D: Unexpected sesterterpenoids as potent S100A8/A9 complex inhibitors for psoriasis treatment

Psoriasis is a common immune-mediated skin disorder manifesting in abnormal skin plaques, and remains a challenge in its management. Blocking the release or inflammatory effects of two proinflammatory molecules of the S100-alarmin family, S100A8 and S100A9, in keratinocytes is a promising strategy for future therapeutic approaches. Undulanoids A-D (1-4), four novel sesterterpenoids possessing a highly congested pentacyclic 6/5/5/6/5 ring system with eight stereogenic centers, including three all-carbon quaternary centers, two quaternary carbon centers at the bridgehead, and a 1,4,11-trimethyltricyclo5.3.1.0^4,11undecane fragment, were isolated from Aspergillus undulatus. Their structures were elucidated by spectroscopic data and single-crystal X-ray diffraction. Strikingly, undulanoid B (2), the most promising lead compound, inhibits the expression of genes related to tumor necrosis factor and interleukin-17 signaling pathways. Furthermore, reverse target prediction, cellular thermal shift assay, and dynamic simulation indicated that compound 2 could target with the expression of S100A9 and keratinocyte proliferation. As the pioneering S100A8/A9 complex and inhibit its secretion. Moreover, compound 2 showed a potent therapeutic effect on the psoriasiform skin lesions induced by imiquimod in mice by inhibiting the expression of S100A9 and keratinocyte proliferation. As the pioneering examples of natural products demonstrate inhibitory action against S100A8/A9 complex, this discovery provides a series of compelling lead compounds with novel molecular scaffold for treating psoriasis.