Nine regioisomeric and stereoisomeric triterpene dimers from Maytenus chuchuhuasca

Naturally occurring dimeric triterpenoids: Occurrence, chemistry and bioactivities

The triterpenes represent one of the most reported subclasses of specialized metabolites from the plant kingdom. They play a key role in the protection of plants and their metabolism in addition to displaying a high structural diversity and large scale of biological activities. The scaffold can undergo several reactions like oxidation or substitution at different positions of the skeleton leading to the formation of several types of compounds. More specifically, triterpene dimer is a small group of compounds found in nature (from plants precisely). Until 2021, the chemical and pharmacological works reported in the literature indicated the identification of 90 natural dimeric triterpenes and 11 synthetic derivatives from 19 plants species and very few of them have been biologically evaluated for their antibacterial, antioxidant, antiproliferative or molluscicide activities. This review aims to compile the literature on the occurrence, chemistry and biological activities of the triterpenoid dimers. To attend this goal, a literature survey has been done in a number of online libraries including Scifinder, PubMed, Web of Science and Google Scholar using keywords terpene, triterpene, dimer, celastroloid without language restriction. This paper provides the easiest access to the information on triterpene dimers for readers and researchers in view to enhancing the continuity of research works on this topic.

Pentacyclic Triterpenoids Isolated from Celastraceae: A Focus in the 13C-NMR Data

The Celastraceae family comprises about 96 genera and more than 1.350 species, occurring mainly in tropical and subtropical regions of the world. The species of this family stand out as important plant sources of triterpenes, both in terms of abundance and structural diversity. Triterpenoids found in Celastraceae species display mainly lupane, ursane, oleanane, and friedelane skeletons, exhibiting a wide range of biological activities such as antiviral, antimicrobial, analgesic, anti-inflammatory, and cytotoxic against various tumor cell lines. This review aimed to document all triterpenes isolated from different botanical parts of species of the Celastraceae family covering 2001 to 2021. Furthermore, a compilation of their ¹³C-NMR data was carried out to help characterize compounds in future investigations. A total of 504 pentacyclic triterpenes were compiled and distinguished as 29 aromatic, 50 dimers, 103 friedelanes, 89 lupanes, 102 oleananes, 22 quinonemethides, 88 ursanes and 21 classified as others.

Naturally occurring [4 + 2] type terpenoid dimers: sources, bioactivities and total syntheses

This review article highlights recent progress on their sources, bioactivities, biosynthetic hypotheses and total chemical syntheses of naturally occurring [4 + 2] type terpenoid dimers.

Biogenesis of Triterpene Dimers from Orthoquinones Related to Quinonemethides: Theoretical Study on the Reaction Mechanism

The biogenetic origin of triterpene dimers from the Celastraceae family has been proposed as assisted hetero-Diels-Alder reaction (HDA). In this work, computational calculation of HDA between natural quinonemethides (tingenone and isopristimerol) and hypothetical orthoquinones has been performed at the M06-2X/6-31G(d) level of theory. We have located all the HDA transition states supporting the biogenetic route via HDA cycloadditions. We found that all reactions take place through a concerted inverse electron demand and asynchronous mechanism. The enzymatic assistance for dimer formation was analyzed in terms of the calculated transition state energy barrier.

Terpenoids from root bark of Celastrus orbiculatus

Phytochemical investigation of root bark of Celastrusorbiculatus afforded 10 terpenoids and eight known compounds. Their structures were established on the basis of spectroscopic and chemical methods. Celastrol and its dimers and adducts displayed moderate inhibitory activity against T cell proliferation. The reaction of celastrol under acidic conditions was undertaken, and a mechanism is presented, which may help towards modification of its structure and elucidation of the biogenetic routes to natural celastrol derivatives.

[Synthesis and modification of triterpenoids with two lupan backbones]

The first derivatives containing two lupan backbones were synthesized by the interaction of betulonic acid chloride with diols (ethylene glycol and diethylene glycol) and monoethanolamine. A modification of ring A of ethylene-l,2-bis(betulonnate) led to its bis(3beta-aminopropyloxy) and bis(3,4-seco-2-cyano) derivatives.

Plant-derived natural product research aimed at new drug discovery

Many important bioactive compounds have been discovered from natural sources using bioactivity-directed fractionation and isolation (BDFl) [Balunas MJ, Kinghorn AD (2005) Drug discovery from medicinal plants. Life Sci 78:431-441]. Continuing discovery has also been facilitated by the recent development of new bioassay methods. These bioactive compounds are mostly plant secondary metabolites, and many naturally occurring pure compounds have become medicines, dietary supplements, and other useful commercial products. Active lead compounds can also be further modified to enhance the biological profiles and developed as clinical trial candidates. In this review, the authors will summarize research on many different useful compounds isolated or developed from plants with emphasis placed on those recently discovered by the authors' laboratories as antitumor and anti-HIV clinical trial candidates.

Triterpenoids

This review covers the isolation and structure determination of triterpenoids including squalene derivatives, lanostanes, cycloartanes, dammaranes, euphanes, tirucallanes, tetranortriterpenoids, quassinoids, lupanes, oleananes, friedelanes, uranes, hopanes, isomalabaricanes and saponins. The literature from January to December 2004 is reviewed and 243 references are cited.

The dihydro-β-agarofuran sesquiterpenoids

Dihydro-Beta-agarofuran sesquiterpenoids are a structurally diverse class of natural products based on tricyclic 5,11-epoxy-5Beta,10alpha-eudesman-4-(14)-ene skeleton. Between January 1990 and June 2006, 462 new dihydro-Beta-agarofuran sesquiterpenoids of 74 structural types have been isolated from about 64 species of Celastraceae, 3 species of Hippocrateaceae and one species of Lamiaceae. The present review covers the chemical and biological activity research of dihydro-Beta-agarofuran sesquiterpenoids in the past 16 years. The chemical research includes structural classification into sesquiterpene polyesters and macrolide sesquiterpene pyridine alkaloids, synthesis of dihydro-Beta-agarofuran as well as extraction, isolation and purification methods. The biological activity research includes activities such as multidrug resistance (MDR) reversal activity, HIV inhibition, cytotoxicity, antitumor activity, antifeedant activity and insecticidal activity with some insights to their modes of actions.

Chromatographic determination of plant saponins—An update (2002–2005)

The developments during 2002-2005 in the methods used for saponin analyses in plant material are presented. There were number of papers published on isolation and identification of new saponins by chromatographic techniques. Some new developments can be found in separation techniques or solid and mobiles phases used. Separation of individual saponins is still complicated and time consuming. This is due to the fact that in most of the plant species saponins occur as a multi-component mixture of compounds of very similar polarities. Thus, to isolate single compound for structure elucidation or biological activity testing, a combination of different chromatographic techniques has to be used, e.g. first separation of the mixture to simpler sub-fractions on reversed phase C18 has to be followed by further purification on normal phase Silica gel column. Especially difficult is determination of saponins in plant material as these compounds do not possess chromophores and their profiles cannot be registered in UV. Most HPLC methods apply not only specific registration at 200-210 nm, but these methods are not applicable for determination of many saponins in plant material at levels lower than 200-300 mg/kg. Some new or improved techniques for quantification of saponins in plant material were published in reviewed period. These include further progress in the application of evaporative light scattering detection (ELSD) for saponin profiling and quantification, which is also not only specific but also more sensitive in comparison to 200-210 nm detection. Some progress in development of new applications for liquid chromatography-electrospray mass spectrometry (LC/ESI/MS) for saponin determination has also been done. This method gives highest sensitivity and on line identification of separated saponins and should be recommended for specialized analyses of extracts and pharmaceutical formulas like the validation of a new assay. From non-chromatographic techniques for saponin determination, a sensitive and compound specific ELISA tests for some saponins were developed.

Two Cangorosin A Type Triterpene Dimers from Maytenus chuchuhuasca

Two new cangorosin A type triterpene dimers, which composed of two triterpene units jointed by two ether linkages between the A and B rings, were isolated from the Brazilian medicinal plant "xuxuá" (Maytenus chuchuhuasca). Structures of new isolates, xuxuasins A (1) and B (2), were established based on several spectroscopic evidences.