Triterpenoids

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.

Epigenetics/epigenomics of triterpenoids in cancer prevention and in health

Triterpenoids are a powerful group of phytochemicals derived from plant foods and herbs. Many reports have shown that they possess chemopreventive and chemotherapeutic effects not only in cell lines and animal models but also in clinical trials. Because epigenetic changes could potentially occur in the early stages of carcinogenesis preceding genetic mutations, epigenetics are considered promising targets in early interventions against cancer using epigenetic bioactive substances. The biological properties of triterpenoids in cancer prevention and in health have multiple mechanisms, including antioxidant and anti-inflammatory activities, cell cycle regulation, as well as epigenetic/epigenomic regulation. In this review, we will discuss and summarize the latest advances in the study of the pharmacological effects of triterpenoids in cancer chemoprevention and in health, including the epigenetic machinery.

Triterpenoids from the stems of Schisandra grandiflora and their biological activity

One new ursane-type triterpenoid (1), named granditriol, along with 14 known compounds (2-15), was isolated from the organic extracts of Schisandra grandiflora stems. The structure of the new compound was elucidated by extensive spectroscopic methods as 28-norursa-12,17,19,21-tetraen-2α,3α,23-triol. These isolates were evaluated for anti-phytopathogenic fungi activity and cytotoxicity against human cancer cell line (HepG2). Asiatic acid (8) and 2α,3α,19α-trihydroxyurs-12-en-28-oic acid (9) inhibited the growth of two plant pathogens, Alternaria alternata and Alternaria solani. In addition, compounds 12, 15, and 11 displayed notable anti-proliferative activity against HepG2 cells. Compound 1 is the first report of 28-nortriterpenoid from the Schisandraceae family. All these were obtained from this plant for the first time.

Early state research on antifungal natural products

Nosocomial infections caused by fungi have increased greatly in recent years, mainly due to the rising number of immunocompromised patients. However, the available antifungal therapeutic arsenal is limited, and the development of new drugs has been slow. Therefore, the search for alternative drugs with low resistance rates and fewer side effects remains a major challenge. Plants produce a variety of medicinal components that can inhibit pathogen growth. Studies of plant species have been conducted to evaluate the characteristics of natural drug products, including their sustainability, affordability, and antimicrobial activity. A considerable number of studies of medicinal plants and alternative compounds, such as secondary metabolites, phenolic compounds, essential oils and extracts, have been performed. Thus, this review discusses the history of the antifungal arsenal, surveys natural products with potential antifungal activity, discusses strategies to develop derivatives of natural products, and presents perspectives on the development of novel antifungal drug candidates.

Lanostanoids from fungi: a group of potential anticancer compounds

Lanostanes are a group of tetracyclic triterpenoids derived from lanosterol. They have relevant biological and pharmacological properties, such as their cytotoxic effects via induction of apoptosis. This review compiles the most relevant lanostanoids studied from 2000 to 2011, principally those isolated from Ganoderma lucidum and other related fungi, such as Poria cocos, Laetiporus sulphureus, Inonotus obliquus, Antrodia camphorata, Daedalea dickinsii, and Elfvingia applanata, which have great potential as anticancer agents because of their cytotoxic or apoptotic effects. The compounds were selected on the basis of their proapoptotic mechanisms, through their ability to modify transcriptional activities via nuclear factors or genes and the activation or inhibition of pro- or antiapoptotic proteins; studies based only on their cytotoxicity were excluded from this review in the absence of complementary studies on their mechanisms of action. A total of 81 compounds from Ganoderma lucidum and other species from this genus are included, as well as 96 compounds isolated from other fungi, principally Poria cocos. Some of these compounds were found to arrest the cell cycle in the G1 phase, increase levels of p53 and Bax, or inhibit the phosphorylation of Erk1/2 or the activation of NF-κB and AP-1. Other lanostanes have inhibitory effects on the growth of androgen prostate carcinoma through increasing the expression of p21, which activates the tumor suppressor protein p53, while other compounds have been shown to selectively inhibit topo II activity without affecting topo I. General considerations concerning the chemical structure-biological activities of these compounds are also discussed.

Sesquiterpenoids and norterpenoids from Vitex negundo

Chemical investigation on the seeds of Vitex negundo has afforded a new furan-containing sesquiterpenoid, negunfurol (1), a new norlabdane-type diterpenoid, negundoal (2), and two new norursane-type triterpenoids, negundonorins A (3) and B (4), together with two know compounds, 3-formyl-4,5-dimethyl-8-oxo-5H-6,7-dihydronaphtho[2,3-b]furan (5) and 3-epi-corosolic acid (6). Their structures and configurations were elucidated by detailed spectroscopic analyses on the basis of NMR, IR, and MS data. Compound 3 was strongly cytotoxic against ZR-75-30 cell line with IC(50) value of 0.56 ± 0.19 μg/mL, whereas compound 1 was most active against HL-60 cell line with IC(50) value of 0.94 ± 0.26 μg/mL.

Formation of Triterpenoids throughout Olea europaea Fruit Ontogeny

Drupes were handpicked from olive (Olea europaea L.) trees, cv chemlali, at 13 distinct stages of fruit development, referred to as weeks after flowering (WAF), and analyzed for their free and esterified sterols and triterpenoids content. These two classes of compounds are synthesized via the acetate/mevalonate pathway and share common precursors up to oxidosqualene (OS). Cyclization of OS in either cycloartenol or beta-amyrin constitutes a branch point between primary (sterol pathway) and secondary (triterpenoid pathway) metabolisms. At the onset of fruit development, i.e., between 12 and 18 WAF, drupes were found to contain high amounts of alpha- and beta-amyrins as well as more-oxygenated compounds such as triterpenic diols (erythrodiol and uvaol) and acids (oleanolic, ursolic and maslinic acids). Concomitantly, sterol precursors were barely detectable. From 21 WAF, when the olive fruit reached its final size and began to turn from green to purple, alpha- and beta-amyrins were no longer present, while 4,4-dimethyl- and 4alpha-methylsterols started to be formed, indicating a redirection of the carbon flux from the triterpenoid pathway towards the sterol pathway. Between 21 and 30 WAF, sterol end products, mainly represented by sitosterol, progressively accumulated and triterpenic diols were replaced by triterpenic acids, essentially maslinic acid. Interestingly, the developing olive fruit was found to accumulate significant amounts of parkeol as an ester conjugate. Whatever the stage of development, triterpenoids represent the major triterpenic compounds of the olive fruit.

Marine natural products

This review covers the literature published in 2005 for marine natural products, with 704 citations (493 for the period January to December 2005) referring to compounds isolated from marine microorganisms and phytoplankton, green algae, brown algae, red algae, sponges, coelenterates, bryozoans, molluscs, tunicates and echinoderms. The emphasis is on new compounds (812 for 2005), together with their relevant biological activities, source organisms and country of origin. Biosynthetic studies, first syntheses, and syntheses that lead to the revision of structures or stereochemistries, have been included.

Biovalorization of friedelane triterpenes derived from cork processing industry byproducts

Here, we describe the synthesis, bioactivity screening, and structure-activity relationships of various synthetic triterpenoids prepared from the cork processing byproducts friedelin (1) and 3-hydroxyfriedel-3-en-2-one (2) via oxidative procedures. The synthesis of compounds 2alpha-trimethylsiloxyfriedelan-3-one (17), friedelin-2,3-lactone (18), friedelin-3-oxime (19), and friedelin-3,4-lactam (20) is also described. We have studied the insecticidal and phytotoxic potential of these compounds, their selective cytotoxic effects on insect and mammalian cells, and their antiparasitic effects. Structural modifications of the A-ring of friedelin (1) improved its insecticidal activity with derivatives 5, 2,3-secofriedelan-2-al-3-oic acid (6), its acetylated derivative 6a, 3beta- and 3alpha-hydroxyfriedelane (9 and 10), 3alpha-hydroxyfriedel-2-one (11), 4beta-hydroxyfriedel-3-one (16), the acetylated 10a, 3,4-secofriedelan-4-oxo-3-oic-acid (14), lactone 18, and the oxime 19 being stronger insecticides than the parent compound. Methyl-3-nor-2,4-secofriedelan-4-oxo-2-oic acid (12) and its acetylated derivative 12a also showed insecticidal activity in contrast to their inactive parent compound 2. The postingestive effects and cytotoxicity of these compounds suggest a multifaceted insecticidal mode of action. These structural modifications did not result in better phytotoxic agents than the parent compounds except for lactam 20 and yielded several moderately active antiparasite derivatives (seco acids 6, 12, 14, and 4beta-hydroxyfriedel-3-one 16) with cytotoxic effects on mammalian cells.

Activity-guided isolation of cytotoxic constituents from the bark of Aglaia crassinervia collected in Indonesia

Activity-guided fractionation of a CHCl(3)-soluble partition of the MeOH extract of the bark of Aglaia crassinervia collected in Indonesia led to the isolation of three new glabretal-type triterpenoids, aglaiaglabretols A-C (1-3), as well as nine known compounds, 3-epi-cabraleahydroxylactone (4), cabraleahydroxylactone (5), rocaglaol (6), 2beta,3beta-dihydroxy-5alpha-pregn-17(20)-(E)-16-one, scopoletin, and mixtures of cabraleadiol and epicotillol and of beta-sitosterol and stigmasterol. The structures of compounds 1-3 were determined on the basis of spectroscopic and chemical methods. The structure of aglaiaglabretol A (1) was confirmed by single-crystal X-ray analysis, and the absolute stereochemistry of this isolate was established by the Mosher ester method. The cytotoxic activity of all isolates and several chemical transformation products obtained in the present study was evaluated. The known cyclopenta[b]benzofuran, rocaglaol (6), was found to be significantly active and comparable in potency to the positive controls, paclitaxel and camptothecin. Aglaiaglabretol B (2) was further tested in an in vivo hollow fiber model.

New developments in natural products-based anti-AIDS research

This review discusses anti-HIV natural products from several compound classes, including terpenoids, coumarins, alkaloids, polyphenols, tannins, and flavonoids. Natural products can provide novel anti-AIDS chemotherapeutic leads that are structurally unique or have new mechanisms of action. The drug discovery and development process proceeds from bioactivity-directed isolation and identification of a promising lead natural product, followed by rational design-based structural modification and structure-activity relationship analyses to optimize the lead compound as a drug candidate. This process is notably exemplified by the discovery of the modified betulinic acid derivative, DSB [PA-457], which is currently in Phase II clinical trial and is the first-in-class HIV maturation inhibitor (MI).