Cipadessains A-K, eleven limonoids from the fruits of Cipadessa cinerascens

Cipacinerasins A-K, structurally diverse limonoids from Cipadessa baccifera

Eleven undescribed limonoids, cipacinerasins A-K, involving of four diverse carbon skeletal types, along with fifteen known analogues, were isolated from the branches and leaves of Cipadessa baccifera. Within them, cipacinerasins A and B feature a rearranged tetrahydropyranyl ring B formed between C-8 and C-30, are unusual miscellaneous-type limonoids. Cipacinerasins E and F are rare trijugin-type limonoids, of which the D-ring δ-lactone is cleaved. Their structures were elucidated on the basis of extensive spectroscopic data (HRESIMS, NMR, UV and IR), electronic circular dichroism (ECD) calculations, and single-crystal X-ray diffraction analysis. All compounds were evaluated in vitro cytotoxicity against five human tumor cell lines (K562, HeLa, PC3, LN-Cap and Hell), and cipacinerasin E showed moderate antitumor activity with IC₅₀ values ranging from 8.0 to 24.8 μM.

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 from Swietenia macrophylla and their antitumor activities in A375 human malignant melanoma cells

Swietelinins A - C (1-3) and swieteliacates F - R (4-16), sixteen new limonoids and 18 known limonoids (17-34) were isolated from Swietenia macrophylla. The absolute configurations of these compounds were defined by using a combination of electronic circular dichroism data analysis and single-crystal X-ray diffraction data. Swieteliacate J (10) is the first limonoid possessing an unusual 8β, 9β-epoxy ring system. All of the compounds were tested for cytotoxicity against four human tumor cell lines (SMMC-7721, SW620, A549, and A375). Compounds 10, 11, and 19 exhibited selectively moderate cytotoxicity against four tumor cell lines, especially 19 exhibited significant cytotoxic effects against A375 with IC₅₀ an value of 9.8 μM and was more active than the positive control, dacarbazine with an IC₅₀ value of 22.4 μM. Compound 19 effectively induced apoptosis of A375, which was associated with G2/M-phase cell cycle arrest. Flow cytometric analysis showed that the treatment by 19 significantly induced A375 cell apoptosis in a dose-dependent manner.

Mexicanolide-type limonoids from the twigs and leaves of Cipadessa baccifera

Twelve previously undescribed mexicanolide-type limonoids, including two pairs of isomers, together with seven known analogues were isolated from the twigs and leaves of Cipadessa baccifera. Their structures were determined by extensive spectroscopic methods and electronic circular dichroism (ECD) calculations. Structural variations mainly occurred at the attachment of C-3 and the carbon residues linked to C-17. 21-deoxo-23-oxofebrifugin A and 3-O-detigloyl-3-O-isobutyryl-21-deoxo-23-oxofebrifugin A are two rare naturally occurring mexicanolide-type limonoids bearing an α,β-unsaturated-γ-lactone motif at C-17. Moreover, cipaferen R is the first degraded tetranortriterpenoid derivative featuring an unique acetyl group at C-17. Some isolated compounds were evaluated for nematicidal, antifungal, cytotoxic (against five human cancer cell lines), and acetylcholinesterase inhibitory activities. No nematicidal and antifungal activities were observed, yet 3-O-detigloyl-3-O-isobutyrylfebrifugin A, febrifugin A, febrifugin, and khaysin T exhibited moderate cytotoxic activity against the tested cells with IC₅₀ values ranging from 18.56 ± 0.27 to 38.00 ± 0.85 μM, and 3-O-detigloyl-3-O-isobutyrylfebrifugin A, granatumin E, khaysin T, and 2'S-cipadesin A showed moderate inhibitory activities against acetylcholinesterase (AChE) at 50 μM.

Seven new guanacastane-type diterpenoids from the fungus Verticillium dahliae

Seven new guanacastane-type diterpenoids, namely dahlianes E-K (1-7), and three known ones (8-10) were isolated from the cultures of the fungus Verticillium dahliae. Their structures were established by extensive spectroscopic data analysis along with Rh₂(OCOCF₃)₄- and Mo₂(OAc)₄-induced electronic circular dichroism (ECD) experiment. Dahliane G showed an 80-fold potentiation effect on the sensitization of doxorubicin at the concentration of 15 μM when screening the reversal activity on doxorubicin-resistant human breast cancer cells (MCF-7/DOX).