Immunosuppressive Diterpenes from Phomopsis sp. S12

New immunosuppressants are needed to assist therapeutic efforts to manage immunological diseases. Along with known compounds 1 – 4 , new diterpenes myrocin E ( 5 ), libertellenone J ( 6 ) and libertellenone K ( 7 ) were isolated from the culture of Phomopsis sp. S12, from the apparently normal seed of Illigera rhodantha (Hernandiaceae). The structures were elucidated by a combination of spectroscopic and computational approaches, in conjunction with the low‐temperature (100 K) single‐crystal X‐ray diffraction with copper K α radiation. Libertellenone J ( 6 ) was shown to reduce significantly the production of NO, IL‐1β, IL‐6 and TNF‐α with an IC 50 range of 2.2–10.2 μ M , and to decrease the levels of iNOS, IL‐1β, IL‐6 and TNF‐α mRNA expression in lipopolysaccharide‐activated macrophages with IC 50 values of 3.5–15.2 μ M . These significant results may inspire the development of new immunosuppressive agents.