Apo-Tirucallane and Tirucallane Triterpenoids and Glycosides from Munronia pinnata as Inhibitors of Spodoptera frugiperda Growth

Apo-tirucallane and tirucallane triterpenoids in Meliaceae plants, which serve as key biosynthetic precursors of botanical insecticidal limonoids, have attracted considerable attention of natural product chemists because of their agricultural relevance. A phytochemical investigation of Munronia pinnata led to the discovery of 20 new (apo)-tirucallane triterpenoids and their glycosides, including 11 apo-tirucallane and 9 tirucallane. Their structures were elucidated by spectroscopic analysis, chemical transformations, quantum chemical calculations, and X-ray crystallography. Their activities against Phytophthora sojae and Spodoptera frugiperda were evaluated, and the results revealed that apo-tirucallane aglycones 1, 6, and 9 reduced larval body weight under the experimental conditions.