A new lactam 28-norlimonoid from the leaves of Azadirachta indica A. Juss. (Meliaceae)

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.

A new liposomal nanocarrier for co-delivery of gedunin and p-glycoprotein siRNA to target breast cancer stem cells

Gedunin is a secondary metabolite found in neem tree. Since the first discovery of this compound, its bio-active properties have been continuously evaluated. However, the low hydrophobicity of gedunin decreases its bioavailability and pharmacokinetic profile. In the present investigation, a new liposomal nanocarrier for co-delivery of gedunin and P-glycoprotein (P-gp) siRNA [siRNA coated liposomal gedunin (Lipo-Ged-siRNA)] was developed to improve the anti-proliferative activity of gedunin. Characteristics of prepared Lipo-Ged-siRNA demonstrated promising effects. Lipo-Ged-siRNA showed greater anti-proliferative effects (IC₅₀-8.5 µg/mL) followed by pure gedunin (IC₅₀- 40.2 µg/mL) in breast cancer stem cells (bCSCs). Immunofluorescence analysis demonstrated reduced expression of P-gp following exposure to Lipo-Ged-siRNA. Furthermore, Lipo-Ged-siRNA affected the expression of ABCB1, Cyclin D1, Bax, p53, and surviving genes in bCSCs.

Pipercyclobutanamide D, a new member of the cyclobutanamide-type alkaloid, from the roots of Piper nigrum

From the EtOH-soluble extract of the roots of Piper nigrum, one new dimeric alkamide, pipercyclobutanamide D (1) was isolated. Its structure was elucidated on the basis of NMR spectroscopic interpretation. The relative configuration of 1 was determined based on the NOESY analysis. Compound 1 showed α-glucosidase inhibitory activity with an IC₅₀ value of 158.5 µM. In addition, compound 1 exhibited cytotoxicity against the MCF-7 and HepG2 cell lines with the IC₅₀ values of 45.6 and 63.9 µM, respectively. Plausible biosynthetic pathway for the formation of 1 was proposed based on regioselective [2 + 2] cycloaddition reaction.