Recent Progress on Limonoids: The Potential, Challenges, and Insights of Chemistry and Biology

Limonoids are an important class of highly oxygenated triterpenoids containing a distinctive 4,4,8-trimethyl-17-furanylsteroid skeleton. To date, over 2700 members, including azadirachtin, toosendanin, limonin, obacunone, nomilin, harrisonin, nimbolide, gedunin, salannin, nimbin, khayanolide, xylocarpin, swietenine, rocaglamide, trichilin, vilasinin, etc., have been isolated from citrus fruits and the plants of the Rutaceae and Meliaceae families. They play a significant role in the discovery of novel drug and pesticide candidates owing to their wide range of biological activities, such as protective, anti-inflammatory, anti-cancer, antimicrobial, and insecticidal properties. Therefore, their potential, challenges, and insights into the chemistry and biology of triterpenoid-type limonoids have recently garnered much attention. The focus of this review is not only to summarize the isolation, total synthesis, and structural modifications of limonoid-type natural products as potential therapeutic and pesticidal agents, but also to highlight the underlying mechanisms of their pharmacological effects from 2017 to 2025. Noteworthily, perspectives were given on the limonoid-type compounds as leads for further development of novel drugs and agrochemicals, and their applications in the future. Hopefully, this review can serve as a comprehensive reference for future research on limonoids and their derivatives in the pharmaceutical and agricultural fields.