A new antibiotic nortriterpene quinone methide from Maytenus catingarum

New insights into the anticancer therapeutic potential of maytansine and its derivatives

Maytansine is a pharmacologically active 19-membered ansamacrolide derived from various medicinal plants and microorganisms. Among the most studied pharmacological activities of maytansine over the past few decades are anticancer and anti-bacterial effects. The anticancer mechanism of action is primarily mediated through interaction with the tubulin thereby inhibiting the assembly of microtubules. This ultimately leads to decreased stability of microtubule dynamics and cause cell cycle arrest, resulting in apoptosis. Despite its potent pharmacological effects, the therapeutic applications of maytansine in clinical medicine are quite limited due to its non-selective cytotoxicity. To overcome these limitations, several derivatives have been designed and developed mostly by modifying the parent structural skeleton of maytansine. These structural derivatives exhibit improved pharmacological activities as compared to maytansine. The present review provides a valuable insight into maytansine and its synthetic derivatives as anticancer agents.

Two new triterpenes isolated from Maytenus guangxiensis C. Y. Cheng et W. L. Sha and their antiproliferative activities

Two new triterpenes, 3β, 7β-dihydroxyolean-12-en-11-one (1) and 3β-O-acetyl-7β-hydroxyolean-12-en-11-one (2), along with four known triterpenes 3β-hydroxyolean-12-en-11-one (3), β-amyrin (4), lup-20(29)-ene-1β, 3β-diol (5) and 1β, 3β-dihydroxy-urs-9(11)-12-diene (6), were isolated from the stems and leaves of Maytenus guangxiensis C. Y. Cheng et W. L. Sha. Their structures were elucidated using 1D and 2D NMR spectroscopy as well as MS and IR experiments. Compounds (3-6) were isolated from M. guangxiensis for the first time. Compounds 1-6 were evaluated for their antiproliferative activities against Eca-109, PANC-1, EJ and HeLa cell lines. The results showed that compounds 1-6 displayed a certain degree of inhibitory effects against the proliferation of various human cancer cell lines.

A Review on Phytochemicals of the Genus Maytenus and Their Bioactive Studies

The genus Maytenus is a member of the Celastraceae family, of which several species have long been used in traditional medicine. Between 1976 and 2021, nearly 270 new compounds have been isolated and elucidated from the genus Maytenus. Among these, maytansine and its homologues are extremely rare in nature. Owing to its unique skeleton and remarkable bioactivities, maytansine has attracted many synthetic endeavors in order to construct its core structure. In this paper, the current status of the past 45 years of research on Maytenus, with respect to its chemical and biological activities are discussed. The chemical research includes its structural classification into triterpenoids, sesquiterpenes and alkaloids, along with several chemical synthesis methods of maytansine or maytansine fragments. The biological activity research includes activities, such as anti-tumor, anti-bacterial and anti-inflammatory activities, as well as HIV inhibition, which can provide a theoretical basis for the better development and utilization of the Maytenus.

Dihydro-β-agarofurans from the roots of the Australian endemic rainforest tree Maytenus bilocularis act as leucine transport inhibitors

Phytochemical studies of the roots of the Australian plant, Maytenus bilocularis, resulted in the identification of six previously undescribed dihydro-β-agarofuran sesquiterpenoids, bilocularins D-I, along with three known natural products, namely 1α,2α,6β,15-tetraacetoxy-9β-benzoyloxydihydro-β-agarofuran, pristimerin, and celastrol. The structures of all compounds were characterized via analysis of 1D/2D NMR and MS data. The absolute configuration of bilocularin D was defined by X-ray crystallography analysis. Bilocularins D and G, 1α,2α,6β,15-tetraacetoxy-9β-benzoyloxydihydro-β-agarofuran, and celastrol inhibited leucine transport in the human prostate cancer cell line LNCaP with IC₅₀ values ranging from 2.5-27.9 μM, which were more potent than the L-type amino acid transporter (LAT) family inhibitor 2-aminobicyclo[2,2,1]-heptane-2-carboxylic acid (BCH). Bilocularins D-F are the first examples of dihydro-β-agarofurans bearing a hydroxyacetate group.

Antiplasmodial sesquiterpene alkaloids from the roots of Maytenus mekongensis

Eight new sesquiterpene alkaloids (1-8) and four known sesquiterpene alkaloids (9-12) have been isolated from the roots of Maytenus mekongensis. Structures were determined using extensive spectroscopic methods. The relative configuration of 7-epi-mekongensine (2) was established by single-crystal X-ray crystallographic analysis. The alkaloids were evaluated for antiplasmodial activity against Plasmodium falciparum, K1 strain, and for cytotoxicity using a panel of cell lines.

Evaluation of antioxidant capacity and synergistic associations of quinonemethide triterpenes and phenolic substances from Maytenus ilicifolia (Celastraceae)

This work describes the isolation of the secondary metabolites identified as the quinonemethides maytenin (1) and pristimerin (2) from Maytenus ilicifolia extracts obtained from root barks of adult plants and roots of seedlings and their quantification by high performance liquid chromatography coupled to a diode array detector. The electrochemical profiles obtained from cyclic voltammetry and a coulometric detector coupled to high-performance liquid chromatography contributed to the evaluation of their antioxidant capacity. The antioxidant properties of individual components and the crude extracts of the root barks of Maytenus ilicifolia were compared and the possible synergistic associations of quinonemethide triterpenes and phenolic substances were investigated by using rutin as a model phenolic compound.

DNA oxidative damage by terpene catechols as analogues of natural terpene quinone methide precursors in the presence of Cu(II) and/or NADH

Natural terpene quinone methides (QM) and their derivatives have been investigated as therapeutics due to their broad antifungal, antibacterial, and antitumor activities. Recently, we reported that a terpene QM was formed from the catechol precursor through the disproportionation of Cu(II)/(I) redox cycle, and extensive DNA damage was observed throughout the oxidation process. In this paper, we investigate DNA damage with a series of terpene catechols as analogues of natural QM precursors and suggest that reactive oxygen species (ROS) are responsible for the observed DNA damage in the Cu(2+)-induced oxidation despite the stereo- and structural difference of these catechol or subsequent oxidation products. In addition, the presence of NADH significantly enhanced the extent of DNA damage by oxidation of these catechols. Especially with alkene catechols 6-7, the extent of DNA damage was independent of the concentration of catechols, implying that NADH enables the continuous production of ROS through the redox cycle of catechols/quinones.

Quinone Methide Formations in the Cu2+-Induced Oxidation of a Diterpenone Catechol and Concurrent Damage on DNA

Terpene quinone methides have been isolated from natural resources and exhibit broad biological activities against bacteria, fungi, and tumor cells through the reactive quinone methide (QM) moiety. The biological potential of the oxidation of terpene QM precursors, however, has not been assessed even though Cu(2+)-induced oxidation of catechol shows detrimental effects on cells. In this study, a diterpenone catechol was investigated as a precursor of terpene QM under aqueous conditions in the presence of Cu2+. Direct QM formation was implied in the Cu(2+)-induced oxidation through the study of thiol addition using HPLC and ESI-MS analysis. In addition, oxidation of the initial QM adduct to a second-QM intermediate was observed. The direct QM oxidation pathway may be unique for diterpenone catechol in the Cu(2+)-induced oxidation and is an addition to the reported isomerization pathway of o-quinones to QMs. The DNA damage by the Cu(2+)-induced oxidation of diterpenone catechol was assessed on a short duplex DNA target. Both direct DNA cleavage and nucleobase oxidation were observed extensively by in situ-generated hydroxyl radicals.

Nine regioisomeric and stereoisomeric triterpene dimers from Maytenus chuchuhuasca

Nine regioisomeric and stereoisomeric triterpene dimers, namely xuxuarine Falpha (1), isoxuxuarine Falpha (2; cangorosin B), 7,8-dihydroisoxuxuarine Falpha (3), isoxuxuarine Gbeta (4), 7,8-dihydroisoxuxuarine Galpha (5), isoxuxuarine Ebeta (6), 7alpha-hydroxyisoxuxuarine Ealpha (7), 7',8'-dihydroxuxuarine Aalpha (8), and 7',8'-dihydroxuxuarine Dbeta (9), were isolated from the Brazilian medicinal plant "xuxuá" (Maytenus chuchuhuasca). Their structures have been elucidated based on several spectroscopic analyses including 2D-NMR experiments, MS spectra and CD spectral studies.

Antifungal properties of pristimerin and celastrol isolated from Celastrus hypoleucus

Pristimerin and celastrol isolated from the roots of Celastrus hypoleucus (Oliv) Warb f argutior Loes exhibited inhibitory effects against diverse phytopathogenic fungi. Pristimerin and celastrol were found to inhibit the mycelial growth of Rhizoctonia solani Kuhn and Glomerella cingulata (Stonem) Spauld & Schrenk in vitro by 83.6 and 62.6%, respectively, at 10 microg ml(-1). Pristimerin showed good preventive effect (96.7% at 100 microg ml(-1)) and curative effect (66.5% at 100 microg ml(-1)) against wheat powdery mildew in vivo. For celastrol, the preventive and curative effects against wheat powdery mildew were 80.5 and 45.4%, respectively, at 100 microg ml(-1).

Antibacterial and anti-inflammatory activities of some plants used for medicinal purposes in Kenya

Aqueous, hexane and methanol extracts of 12 plant species, traditionally used in Kenya for treatment of ailments of infectious and/or inflammatory nature were screened for in vitro antibacterial and anti-inflammatory activities. Antibacterial activity was tested using the agar diffusion method while anti-inflammatory activity was tested using the cyclooxygenase (COX-1) assay. All the antibacterial activity was against Gram-positive bacteria with nine plant species showing some activity against Staphylococcus aureus. The highest activity was found in the methanol extracts of Maytenus senegalensis, Plectranthus barbatus, Zanthoxylum chalybeum, Zanthoxylum usambarense and hexane extracts of Spiranthes mauritianum. All the plant species showed some anti-inflammatory activities. In most cases, methanol extracts caused higher inhibition than aqueous and hexane extracts.

Bioactive 12-oleanene triterpene and secotriterpene acids from Maytenus undata

The aerial parts of Maytenus undata yielded four new 12-oleanene and 3,4-seco-12-oleanene triterpene acids, namely, 3-oxo-11alpha-methoxyolean-12-ene-30-oic acid (1), 3-oxo-11alpha-hydroxyolean-12-ene-30-oic acid (2), 3-oxo-olean-9(11), 12-diene-30-oic acid (3), and 3,4-seco-olean-4(23),12-diene-3, 29-dioic acid (20-epi-koetjapic acid) (5), together with the known 3, 11-dioxoolean-12-ene-30-oic acid (3-oxo-18beta-glycyrrhetinic acid) (4), koetjapic acid (6), and the 12-oleanene artifact 3-oxo-11alpha-ethoxyolean-12-ene-30-oic acid (7). Koetjapic acid (6) inhibited the growth of Staphylococcus aureus, methicillin-resistant S. aureus, and Pseudomonas aeruginosa, with an MIC range of 3.125-6.25 microg/mL. The new 3,4-secotriterpene acid 20-epi-koetjapic acid (5) potently inhibited rat neonatal brain microglia phorbol ester-stimulated thromboxane B(2) (IC(50) = 0.5 microM) and superoxide anion (IC(50) = 1.9 microM) generation.