Mangiterpenes A–C and 2′,3′-seco-manginoid C, four sesquiterpene/monoterpene–shikimate–conjugated spirocyclic meroterpenoids from Guignardia mangiferae

Abstract

Mangiterpenes A–C and 2′,3′-seco-manginoid C, four undescribed sesquiterpene/monoterpene–shikimate–conjugated meroterpenoids with spiro ring systems, were isolated from Guignardia mangiferae. The structures and absolute configurations of these compounds were established by comprehensive spectroscopic analyses and electronic circular dichroism (ECD) calculations. Mangiterpenes A–C represent the first examples of sesquiterpene–shikimate-conjugated spirocyclic meroterpenoids, and 2′,3′-seco-manginoid C features an unexpected 2′,3′-seco-manginoids skeleton. Mangiterpene C strongly inhibited the production of NO inducted by LPS, with an IC50 value of 5.97 μM. It showed an anti-inflammatory effect by means of blocking in the NF-κB signaling pathway and decreasing the expression of inflammatory mediators.