Naturally Occurring Norsteroids and Their Design and Pharmaceutical Application

The main focus of this review is to introduce readers to the fascinating class of lipid molecules known as norsteroids, exploring their distribution across various biotopes and their biological activities. The review provides an in-depth analysis of various modified steroids, including A, B, C, and D-norsteroids, each characterized by distinct structural alterations. These modifications, which range from the removal of specific methyl groups to changes in the steroid core, result in unique molecular architectures that significantly impact their biological activity and therapeutic potential. The discussion on A, B, C, and D-norsteroids sheds light on their unique configurations and how these structural modifications influence their pharmacological properties. The review also presents examples from natural sources that produce a diverse array of steroids with distinct structures, including the aforementioned A, B, C, and D-nor variants. These compounds are sourced from marine organisms like sponges, soft corals, and starfish, as well as terrestrial entities such as plants, fungi, and bacteria. The exploration of these steroids encompasses their biosynthesis, ecological significance, and potential medical applications, highlighting a crucial area of interest in pharmacology and natural product chemistry. The review emphasizes the importance of researching these steroids for drug development, particularly in addressing diseases where conventional medications are inadequate or for conditions lacking sufficient therapeutic options. Examples of norsteroid synthesis are provided to illustrate the practical applications of this research.

Triterpenoids from Dysoxylum genus and their biological activities

This study aims to analyze the ethnobotanical, chemical, and biological activities of triterpenoid compounds isolated from the Dysoxylum genus of the Meliaceae family between 1974 and 2021. The species are mainly distributed in Africa, Asia, and Australia, and used as a traditional medicine to treat various diseases. Triterpenoid was first isolated in 1976 and as tetranortriterpenoid or limonoid, it was named dysobinin. Several studies were conducted for more than 40 years on the plants' stems, bark, and leaves, where approximately 279 triterpenoid compounds from several groups such as dammarane, nortriterpenoid, oleanane, lupane, tirucallane, cyclolanostane, or cycloartane, glabretal, and cycloapoeuphane-types were isolated with some synthetic products. In addition, the hypothetical route of triterpenes biosynthesis from this genus was identified, and tirucallane-type were reported to be 37.6% of the total compounds. The anti-malarial, anti-feedant, antimicrobial, anti-inflammatory, antioxidant, vasodilative effect, anti-viral, cortisone reductase, and cytotoxic activities of the extract were also evaluated. The results showed the necessity of using the triterpenoid compounds from the Dysoxylum genus in traditional medicine and the discovery of new drugs.

Three new ring-A modified ursane triterpenes from Davidia involucrata

Three new ursane triterpenes, 3α,19α-dihydroxy-2-nor-urs-12-en-23,28-dioic acid-23-methyl ester (1), 19α,23-dihydroxy-3-oxo-2-nor-urs-12-en-28-oic acid (2), and 2,3-seco-3-methoxy-3,19α,23-trihydroxy-urs-12-en-2-al-28-oic acid (3), were isolated from the MeOH extract of the branch barks of Davidia involucrata, together with six known compounds. Their structures were elucidated by means of various spectroscopic analyses. The isolated triterpenes provide important evolutionary and chemotaxonomic knowledge about the monotypic genus Davidia. Five of the identified compounds showed moderate cytotoxicities against the cell proliferation of SGC-7901, MCF-7, and BEL-7404 with IC50 range from 7.26 to 47.41 μM.

Limonoids and triterpenoids from the twigs and leaves of Dysoxylum hainanense

Four new limonoids, dysohainanins A–D (1–4), and two new triterpenoids, dysohainanins E and F (5 and 6), together with seven known ones were isolated from the twigs and leaves of Dysoxylum hainanense Merr. The structures of the new compounds were determined by a variety of spectroscopic methods. The cytotoxic activities of these compounds were evaluated, and the known compound ent-19-nor-4,16,18-trihydroxy-8(14)-pomaren-15-one (13) showed in vitro cytotoxicity against HL-60, A-549, MCF-7, and SW480 cells, with IC₅₀ values of 24.3, 28.1, 30.7, and 22.5 µM, respectively. Compounds 2 and 3 were tested their insecticidal activities using brine shrimp and both of them were inactive.

Sesquiterpenes from Dysoxylum oliganthum and Dysoxylum excelsum

Three new sesquiterpenes (1-3), (6R,7S,11R,10S)-15-hydroxy-sesquisabinene hydrate (1), (6R,7R,11S,10S)-15-hydroxy-sesquisabinene hydrate (2), and (6R,7R,10S)-15-hydroxy-zingiberenol (3), along with three known compounds, were isolated from the stems of Dysoxylum oliganthum; and three new isodaucane (salvionane) sesquiterpenes, namely isodauc-6-ene-10β,14-diol (4), 4-epi-isodauc-6-ene-10β,14-diol (5), and 4-epi-6α,10β-dihydroxy-artabotrol (6) together with 15 known compounds were isolated from the twigs and leaves of D. excelsum. Their structures were established on the basis of extensive spectroscopic analysis and chemical shifts. The absolute configuration of C-10 in compounds 1-3 of a rare class was determined by using Snatzke's method.

Complete 1H and 13C NMR data assignment of protolimonoids from the stem barks of Aphanamixis grandifolia

Seven new protolimonoids, named aphagranins A-G (1-7), along with four known compounds, were isolated from the ethanol extract of the stem barks of Aphanamixis grandifolia. Structure elucidation and signal assignments were achieved on the basis of spectral and chemical evidences.

Triterpenoids

This review covers the isolation and structure determination of triterpenoids, including squalene derivatives, protostanes, lanostanes, holostanes, cycloartanes, dammaranes, euphanes, tirucallanes, tetranortriterpenoids, quassinoids, lupanes, oleananes, friedelanes, ursanes, hopanes, serratanes and saponins; 278 references are cited.