New amide, chalcone, and flavonoid derivatives from the leaf and fruit extracts of Melodorum siamensis

Melodorum siamensis, locally known as Nom-Maeo, is a scandent shrub native to Thailand belonging to the Annonaceae family. Previous phytochemical investigations described chalcones, flavonoids, and amides from the leaves of M. siamensis. Some chalcone and amide derivatives showed interesting biological activities, including, cytotoxicity and anti-inflammatory activities. In our study, four new chalcones, a new flavonoid, a new amide, and 19 known compounds were acquired from the fruits and the leaves of M. siamensis using chromatographic techniques. Scelemic mixtures of chalcone dimer (1) and the amide derivative (2) were obtained and the enantiomers were separated by semipreparative chiral HPLC. The structures were established by 1D and 2D NMR, and MS data analyses. The absolute configuration of 1 was determined by experimental and calculated ECD data, while the configurations of 2 and 8 were determined by X-ray diffraction analysis. A biosynthetic pathway for 1, 2, and 8 was also proposed. One compound showed significant activity against NF-κB with an IC₅₀ value of 9 µM in MIN-6 cells, the other compounds were inactive.

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• References

• 1 Prawat U, Chairerk O, Phupornprasert U, Salae AW, Tuntiwachwuttikul P. Two new C-benzylated dihidrochalcon derivatives from the leaves of Melodorum siamensis . Planta Med 2013; 79: 83-86
• 2 Somsrisa J, Meepowpan P, Krachodnok S, Thaisuchat H, Puntanitya S, Nantasaen N. et al. Dihydrochalcones with anti-inflammatory activity from leaves and twigs of Cyathostemma argenteum . Molecule 2013; 18: 6898-6907
• 3 Jaidee W, Andersen RJ, Chavez MAG, Wang YA, Patrick BO, Pyne SG. et al. Amides and flavonoids from the fruits and leaf extracts of Melodorum siamensis . J Nat Prod 2019; 82: 283-292