The Terpenoid Alkaloids of Colobognath Millipedes: Insights into Structural Diversity and Function

Colobognatha, a group of millipedes (Diplopoda) known for their unique biological traits (<i>e.g.,</i> brood care and sociality), is the only group among millipedes to produce terpenoid alkaloids. Before 2020, only four terpenoid alkaloids had been identified; however, recent studies have resulted in a surge of new chemical discoveries and research into their ecological and biochemical roles. In this review, we outline the social characteristics of Colobognatha, the chemical investigations of their defensive secretions, and the bioactivity of the terpenoid alkaloids with a particular emphasis on new findings. We conclude by summarizing gaps in the research on these chemicals and provide insights into future research directions.