Bioactive Limonoids and Triterpenoids from the Fruits of Melia azedarach

Unveil the mechanism for EHMT -- A novel triterpenoid inhibits proliferation and induces apoptosis in colon cancer through ROS-mediated JNK signaling pathway

Colon cancer ranks among the most prevalent malignancies worldwide, trailing only lung and breast cancer in incidence. Despite the availability of numerous therapeutic strategies, the burden of new cases and fatalities remains high in countries undergoing socioeconomic transitions. Natural products offer promising avenues for developing more effective and less toxic anticancer agents, expanding the clinical arsenal. In this investigation, we isolated a triterpenoid, (21 S,23 R,24 R)-21,23-epoxy-24-hydroxy-21-methoxytirucalla-7,25-dien-3-one (EHMT), from the fruits of Melia azedarach L., which exhibited significant inhibitory activity against colon cancer cells while sparing normal cells. EHMT effectively curtailed colony formation and induced apoptosis and cell cycle arrest in the HCT116 cell line. Furthermore, EHMT prompted the generation of reactive oxygen species (ROS) and the depolarization of mitochondrial membrane potential. Notably, EHMT treatment triggered ROS-mediated cell apoptosis via activation of the JNK signaling pathway in HCT116 cells. Additionally, our findings extended to Caenorhabditis elegans, where EHMT induced ROS accumulation and apoptosis. Collectively, these findings position EHMT as a promising candidate for the development of anticancer agents in the treatment of colon cancer, offering new hope in the battle against this formidable disease.

New anti-inflammatory limonoids from the fruits of Melia azedarach

The phytochemical study of the fruits of Melia azedarach (Meliaceae) led to the isolation and characterisation of two novel natural limonoids1-deoxy- 3, 20-dicinnamoyl-11-methoxy-meliacarpinin (1) and 12β- O- methyl nimbolinin A (2), along with twelve known limonoids. Its structure was identified by 1D- and 2D-NMR, HR-ESI-MS and comparison with published data. The anti-inflammatory effect of the compounds was measured in vitro in RAW 264.7 cells by evaluating the production of NO stimulated by LPS. Compounds 1, 8 and 14 indicated significant anti-inflammatory effect with inhibition rate of 11.76, 8.45 and 6.59 μM, respectively. Limonoid 1 significantly inhibited the production of NO, TNF-α and IL-1β in RAW 264.7 cells. Therefore, limonoid derivative may be a promising source of bioactive metabolite for inflammatory diseases.

Limonoids from the roots of Melia azedarach and their anti-inflammatory activity

Twelve undescribed limonoids, meliazedarines J-U (1-12), along with a known one, were isolated from the roots of Melia azedarach. Their structures were elucidated by extensive spectroscopic investigations, X-ray diffraction analyses, and ECD calculations. Compounds 1-8 were identified as ring intact limonoids, while compounds 9-12 were established as ring C-seco ones. The anti-inflammatory potential of compounds 1-4, 6, 8, 9, and 11-13 was evaluated on macrophages. Compounds 1, 3, 4, 6, and 9 significantly suppressed nitric oxide production in lipopolysaccharide (LPS)-induced RAW 264.7 macrophages, among them compound 3 showed the best inhibitory effect with an IC50 value of 7.07 ± 0.48 μΜ. Furthermore, compound 3 effectively reduced interleukin-1β secretion in LPS plus nigericin-induced THP-1 macrophages by inhibiting NLRP3 inflammasome activation. The results strongly suggested that limonoids from the roots of M. azedarach might be candidates for treating inflammation-related diseases.

Triterpenoids from the fruits of Melia azedarach L. and their cytotoxic activities

Eleven undescribed tetracyclic triterpenoids, meliazedarachins A-K, along with twenty-six known compounds were isolated from the fruits of Melia azedarach L.. Their structures were determined by HRESIMS, UV, IR, NMR, X-ray diffraction, electronic circular dichroism (ECD) spectra, and the modified Mosher's method. The cytotoxic activities of all the isolates were measured. Meliazedarachin K and mesendanin N showed cytotoxicity against five human cancer cell lines with IC₅₀ values ranging from 9.02 to 31.31 μM. Meliazedarachin K showed significant cytotoxicity against HCT116 cell line with IC₅₀ value of 9.02 ± 0.84 μM. 21α-methylmelianodiol showed significant cytotoxicity against HCT116 and RKO cell lines with IC₅₀ values of 10.16 ± 1.22 and 8.57 ± 0.80 μM, respectively.

Research progress of meliaceous limonoids from 2011 to 2021

Covering: July 2010 to December 2021Limonoids, a kind of natural tetranortriterpenoids with diverse skeletons and valuable insecticidal and medicinal bioactivities, are the characteristic metabolites of most plants of the Meliaceae family. The chemistry and bioactivities of meliaceous limonoids are a continuing hot area of natural products research; to date, about 2700 meliaceous limonoids have been identified. In particular, more than 1600, including thirty kinds of novel rearranged skeletons, have been isolated and identified in the past decade due to their wide distribution and abundant content in Meliaceae plants and active biosynthetic pathways. In addition to the discovery of new structures, many positive medicinal bioactivities of meliaceous limonoids have been investigated, and extensive achievements regarding the chemical and biological synthesis have been made. This review summarizes the recent research progress in the discovery of new structures, medicinal and agricultural bioactivities, and chem/biosynthesis of limonoids from the plants of the Meliaceae family during the past decade, with an emphasis on the discovery of limonoids with novel skeletons, the medicinal bioactivities and mechanisms, and chemical synthesis. The structures, origins, and bioactivities of other new limonoids were provided as ESI. Studies published from July 2010 to December 2021 are reviewed, and 482 references are cited.

Limonoids with Diverse Oxidation Patterns of C-12 Indicating a Complete Ring C-seco Biogenetic Pathway from Munronia unifoliolata

Munrolins A-Q (1-17), 17 new ring C-seco limonoids with diverse oxidative patterns of C-12, together with nine known analogues (18-26), were isolated from the CH₂Cl₂ extract of Munronia unifoliolata. The planar structures were elucidated by a combination of 1D and 2D NMR and HR-MS analyses, while the absolute configurations were confirmed by ECD calculations and single-crystal X-ray diffraction. Munrolins A (1) and B (2) were first identified as ring C-seco limonoids with a 12,13-ether bridge moiety. Munrolins C-J (3-10) have a rare reduced primary alcohol fragment, while munrolin Q (17) has an unusual ketal fragment formed by dehydration of C-12/14. These limonoids with diverse alcohol and aldehyde type C11/12 branches may be generated through different degrees of reduction after the Baeyer-Villiger oxidation at the C ring, as key intermediates to supplement the biogenetic pathway of ring C-seco limonoids. Compounds 11, 19, and 26 could reverse the multidrug resistance of MCF-7/doxorubicin cells with reversal fold values of 5.2, 4.5, and 18.3, respectively.