Meliaceous Limonoids: Chemistry and Biological Activities

Inhibition of the P2X7/NLRP3 Inflammasome Signaling Pathway by Deacetylgedunin from Toona sinensis

Limonoids are considered the effective part in Meliaceae plants that exert anti-inflammatory effects. Gedunin-type limonoids specifically have anti-inflammatory effects. However, the role of gedunin-type limonoids in the inflammatory diseases mediated by NLRP3 inflammasome remains to be explored. We found that deacetylgudunin (DAG), a gedunin-type limonoid from Toona sinensis, had similar anti-inflammatory effects and lower toxicity than gedunin. Further studies showed that DAG down-regulated the NF-κB pathway, inhibited K⁺ efflux and ROS release, inhibited ASC oligomerization, and significantly weakened the interaction of NLRP3 with ASC and NEK7. Furthermore, DAG could not further inhibit IL-1β secretion and K⁺ efflux when combined with the P2X7 inhibitor A438079. In conclusion, our research revealed that DAG exerted an anti-inflammatory effect by inhibiting the P2X7/NLRP3 signaling pathway and enriched the application of gedunin-type limonoids in inflammatory diseases driven by the NLRP3 inflammasome.

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.

Insecticidal Triterpenes in Meliaceae: Plant Species, Molecules, and Activities: Part II (Cipadessa, Melia)

Plant-originated triterpenes are important insecticidal molecules. Research on the insecticidal activity of molecules from Meliaceae plants has always been a hotspot due to the molecules from this family showing a variety of insecticidal activities with diverse mechanisms of action. In this paper, we discussed 116 triterpenoid molecules with insecticidal activity from 22 plant species of five genera (Cipadessa, Entandrophragma, Guarea, Khaya, and Melia) in Meliaceae. In these genera, the insecticidal activities of plants from Entandrophragma and Melia have attracted substantial research attention in recent years. Specifically, the insecticidal activities of plants from Melia have been systemically studied for several decades. In total, the 116 insecticidal chemicals consisted of 34 ring-intact limonoids, 31 ring-seco limonoids, 48 rearranged limonoids, and 3 tetracyclic triterpenes. Furthermore, the 34 ring-intact limonoids included 29 trichilin-class chemicals, 3 azadirone-class chemicals, and 1 cedrelone-class and 1 havanensin-class limonoid. The 31 ring-seco limonoids consisted of 16 C-seco group chemicals, 8 B,D-seco group chemicals, 4 A,B-seco group chemicals, and 3 D-seco group chemicals. Furthermore, among the 48 rearranged limonoids, 46 were 2,30-linkage group chemicals and 2 were 10,11-linkage group chemicals. Specifically, the 46 chemicals belonging to the 2,30-linkage group could be subdivided into 24 mexicanolide-class chemicals and 22 phragmalin-class chemicals. Additionally, the three tetracyclic triterpenes were three protolimonoids. To sum up, 80 chemicals isolated from 19 plant species exhibited antifeedant activity toward 14 insect species; 18 chemicals isolated from 17 plant species exhibited poisonous activity toward 10 insect species; 16 chemicals isolated from 11 plant species possessed growth-regulatory activity toward 8 insect species. In particular, toosendanin was the most effective antifeedant and insect growth-regulatory agent. The antifeedant activity of toosendanin was significant. Owing to its high effect, toosendanin has been commercially applied. Three other molecules, 1,3-dicinnamoyl-11-hydroxymeliacarpin, 1-cinnamoyl-3-methacryl-11-hydroxymeliacarpin, and 1-cinnamoyl-3-acetyl-11-hydroxymeliacarpin, isolated from Meliaazedarach, exhibited a highly poisonous effect on Spodoptera littoralis; thus, they deserve further attention.

Pentacyclic triterpenes from the leaves extract of Sandoricum koetjape

Three new pentacyclic triterpenes, trivially named sandkoetjapic acids A-C (1-3), have been isolated from the leaves extract of Sandoricum koetjape, along with the known triterpenes 3-oxo-olean-12-en-29-oic (4), bryonolic (5), and bryononic (6) acids. The structures of the new triterpenes were determined mainly by NMR spectroscopic and mass spectroscopic data. The isolation of these pentacyclic triterpenes in the plant's leaves is for the first time. Preliminary biological evaluation of 1-6 was done against eight receptor tyrosine kinases (RTKs), including EGFR, HER2, HER4 (epidermal growth factor receptor), IGF1R, InsR (insulin receptor), KDR (kinase insert domain receptor), and PDGFRα/-β (platelet-derived growth factor receptor), and their inhibitory properties against β-lactamase. The results showed that none of them were active both as the inhibitors of these RTKs and β-lactamase.

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.

Metabolic Engineering of Saccharomyces cerevisiae for de Novo Dihydroniloticin Production Using Novel CYP450 from Neem (Azadirachta indica)

Azadirachtin, a limonoid isolated from the neem tree, has attracted considerable interest due to its excellent performance in pest control. Studies have also reported pharmaceutical activities of dihydroniloticin, an intermediate in azadirachtin biosynthesis, but these pharmaceutical activities could not be validated due to the limited supply. In this study, AiCYP71CD2 was first identified as involved in azadirachtin biosynthesis in neem by expressing it in Nicotiana benthamiana and yeast (Saccharomyces cerevisiae). Homology modeling and molecular docking analysis revealed that AiCYP71CD2 may exhibit a higher ability in catalyzing tirucalla-7,24-dien-3β-ol into dihydroniloticin compared with MaCYP71CD2 from Melia azedarach L. G310 was identified as the critical residue responsible for the higher catalytic ability of AiCYP71CD2. Condon-Optimized AiCYP71CD2 greatly improved the catalytic efficiency in yeast. De novo dihydroniloticin production using the novel AiCYP71CD2 was achieved by constructing the S. cerevisiae DI-3 strain, and the titer could reach up to 405 mg/L in a fermentor, which was an alternative source for dihydroniloticin.

Triterpenes and limonoids of Cedrela: Distribution, biosynthesis, and 1 H and 13 C NMR data

Cedrela genus, a member of the Meliaceae family, presents both chemical characteristics associated with and those that distinguish it from the rest of its members. The presence of triterpenes and limonoids is the characteristic of the Meliaceae family, but the class and type of these chemical constituents are distinctive for each genus. Cedrela includes cycloartane, ursane, oleanane, tirucallane, butyrospermane, and apotirucallane triterpenes, and its limonoids belongs to six class and nine types, known as class Ia-type havanensines, class Ib-type delevoyin, class II-type gedunin, class IIIb-type andirobin, class IIIg-type mexicanolide, class IVa-type evoludone, class Va-type obacunol, class V-type limonin, and class VIII. Each of these structural arrangements includes specific traits, defined by their biosynthetic origin, which can be established by means of structural elucidation techniques, particularly ¹ H and ¹³ C NMR, which assisted by 2D NMR techniques, allowing to deduce their structures unequivocally. The constant presence of these skeletal arrangements in Cedrela ensures that they are its chemophenetic markers and their recurrence is an important criterion for their identity. This review is a compilation of the occurrence of triterpenes and limonoids in Cedrela genus, detailing their biosynthetic association and collecting and organizing their NMR data, with the purpose of facilitating its location, analysis, and use in the phytochemical study of species from this genus.

Synthesis of (-)-melazolide B, a degraded limonoid, from a natural terpene precursor

Degraded limonoids are a subclass of limonoid natural products that derive from ring-intact or ring-rearranged limonoids. Establishment of robust synthetic routes to access them could provide valuable materials to identify the simplest active pharmacophore responsible for the observed biological activities of the parent molecules. This communication delineates the development of a divergent strategy to furnish melazolide B and several other related congeners from a common keto-lactone intermediate, which was rapidly assembled from α-ionone. A chemoselective carbonyl α,β-dehydrogenation and a Wharton reduction were key strategic steps in this synthetic pathway.

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.

Limonoids From the Genus Melia (Meliaceae): Phytochemistry, Synthesis, Bioactivities, Pharmacokinetics, and Toxicology

Limonoids, as the vital bioactive chemical compounds in genus Melia plants, have attracted significant attention owing to their exclusive structural characteristics and remarkable biological activity. These compounds can be usually classified into two categories, including the ring-intact group and the ring-C-seco group. Benefiting from the development of separation and analysis technology, more than 200 limonoids have been isolated and identified from this genus. There is growing evidence that limonoids from genus Melia possess diverse pharmacological activities, especially anti-cancer effects, insecticidal activities, and anti-botulism effects. Toosendanin, one of the paramount limonoids, was considered as the pivotal bioactive marker in two medicinal herbs, including Melia toosendan Sieb. et Zucc and Melia azedarach L. In particular, limonoids are found to exhibit non-negligible toxic effects, a finding which needs further research. Besides this, the lack of clinical research data seriously hinders its further development and utilization, and necessary clinical trials should be taken into consideration. In this review, we systematically summarized the phytochemical compounds and their synthesis methods, pharmacological activities, and the structure–activity relationship, pharmacokinetics, and toxicology of genus Melia-derived limonoids. We believe that this up-to-date review could provide scientific evidence for the application of limonoids as agents beneficial to health in future clinical practice.

An Insight into the Dermatological Applications of Neem: A Review on Traditional and Modern Aspect

BACKGROUND

Dermatological disorders are cutaneous infirmities which are frequently occurring and increasing at an alarming rate. These range from mild itching/redness (dermatitis) to fatal skin cancers and has posed a major health concern. Azadirachta indica A. Juss (commonly known as neem), a member of Meliaceae family, is an Indian medicinal plant which has been known for its health promoting effects since ancient times.

OBJECTIVE

The review highlights the traditional practices, pharmacological aspects, and formulatory approach of neem for the treatment of dermatological disorders. Further, recent patents and novel delivery systems (developed and in pipeline) improving skin delivery and therapeutic profile of neem are discussed.

RESULTS

Neem is a traditional medicinal plant that has been employed for the prevention and treatment of numerous ailments covering systemic and topical disorders. Scientific studies have validated the traditional claims of neem and attributed these health benefits to the presence of more than 300 structurally diverse and complex compounds. It possesses anti-inflammatory, antibacterial, analgesic, antiviral, antifungal, immunomodulatory and antioxidant activities which substantiate its use as skin therapy. Various novel formulations and associated patents that improved the permeability of neem based products across skin could be found in literature.

CONCLUSION

Critical appraisal of available literature revealed that neem possesses anti-microbial, anti-inflammatory, antioxidant and antiseptic properties. Thus it has the potential to be developed as a single effective therapy for the management of multimodal skin disorders. Further, pharmaceutical tailoring of neem by implication of novel carriers could enhance its penetrability across skin.

Insecticidal Triterpenes in Meliaceae: Plant Species, Molecules and Activities: Part Ⅰ (Aphanamixis-Chukrasia)

Plant-originated triterpenes are important insecticidal molecules. The research on insecticidal activity of molecules from Meliaceae plants has always received attention due to the molecules from this family showing a variety of insecticidal activities with diverse mechanisms of action. In this paper, we discuss 102 triterpenoid molecules with insecticidal activity of plants of eight genera (Aglaia, Aphanamixis, Azadirachta, Cabralea, Carapa, Cedrela, Chisocheton, and Chukrasia) in Meliaceae. In total, 19 insecticidal plant species are presented. Among these species, Azadirachta indica A. Juss is the most well-known insecticidal plant and azadirachtin is the active molecule most widely recognized and highly effective botanical insecticide. However, it is noteworthy that six species from Cedrela were reported to show insecticidal activity and deserve future study. In this paper, a total of 102 insecticidal molecules are summarized, including 96 nortriterpenes, 4 tetracyclic triterpenes, and 2 pentacyclic triterpenes. Results showed antifeedant activity, growth inhibition activity, poisonous activity, or other activities. Among them, 43 molecules from 15 plant species showed antifeedant activity against 16 insect species, 49 molecules from 14 plant species exhibited poisonous activity on 10 insect species, and 19 molecules from 11 plant species possessed growth regulatory activity on 12 insect species. Among these molecules, azadirachtins were found to be the most successful botanical insecticides. Still, other molecules possessed more than one type of obvious activity, including 7-deacetylgedunin, salannin, gedunin, azadirone, salannol, azadiradione, and methyl angolensate. Most of these molecules are only in the primary stage of study activity; their mechanism of action and structure–activity relationship warrant further study.

High Value-Added Application of Natural Products in Crop Protection: Semisynthesis and Acaricidal Activity of Limonoid-Type Derivatives and Investigation of Their Biocompatible O/W Nanoemulsions as Agronanopesticide Candidates

The increasingly serious resistance of Tetranychus cinnabarinus Boisduval to a wide range of insecticides/acaricides poses a major challenge to their control. The citrus processing industry generates a huge quantity of various wastes that contain many limonoids. To effectively utilize these byproducts and discover more potent green acaricidal molecules as sustainable alternatives for traditional resistant pesticides, various limonoid-type derivatives (halogenated/seven-membered lactam derivatives of obacunone and halogenated/oxime esters/oxime ethers/seven-membered lactam derivatives of limonin) were synthesized based on a diversity-oriented synthetic strategy. The key steric configurations of 10 derivatives were further confirmed by X-ray crystallography. Compound 9m, which displayed greater than 9.7-fold potent acaricidal activity of limonin, was of preeminence. In addition, some interesting structure-activity relationships were observed. Moreover, a biocompatible O/W nanoemulsion delivery system was used to prepare the limonin-based agronanoacaricide, which exhibited pronounced control efficiency against T. cinnabarinus Boisduval in the greenhouse. This systematic investigation will provide valuable information and guidance for future value-added applications of novel eco-friendly natural product-based nanopesticides.

Lethal and Sublethal Effects of Annona spp. Derivatives on Bemisia tabaci MEAM 1 (Hemiptera: Aleyrodidae) in Tomato

The whitefly Bemisia tabaci(Gennadius) MEAM 1 is one of the main insect species that colonize tomato plants and cause direct and indirect damage. The use of botanical derivatives may be a valuable method of insect control to reduce the inappropriate use of synthetic insecticides on crops. In this study, we evaluated the bioactivity of ethanolic extracts prepared from Annonaceae species compared to that of the commercial insecticides based on acetogenins (Anosom® 1 EC, anonine 10,000 mg L^-1) and thiamethoxam (Actara® 250 WG) on eggs, nymphs, and adults of the whitefly in tomato. Initially, the effects of the ethanolic seed extracts of Annona mucosa (Jacq.), Annona muricata L., and Annona sylvatica A.St.-Hil on adult insect behavior were evaluated. The rates of infestation and oviposition deterrence indicated the inhibitory effects of the extract of A. muricata (500 mg L^-1). Then, the possible systemic effects of the extracts were evaluated; however, no effects on nymphal development or insect viability were observed. The LC₅₀ and LC₉₀ of the ethanolic extract of A. mucosa seeds at 500 mg L^-1 (10.83 and 200.24 mg L^-1, respectively) were estimated and were used in ovicidal tests and compared to positive (Actara® 250 WG and Anosom® 1 EC), and negative controls (water: acetone, 1:1 v/v). At LC₉₀, fewer eggs (35.00%) had hatched at 13 days after application than in the other treatments. The results of this study demonstrate the potential use of botanical derivatives of Annona spp. for the management of B. tabaci MEAM 1 in tomato.

Pseudocedrela kotschyi: a review of ethnomedicinal uses, pharmacology and phytochemistry

CONTEXT

Pseudocedrela kotschyi (Schweinf) Harms (Meliaceae) is an important medicinal plant found in tropical and subtropical countries of Africa. Traditionally, P. kotschyi is used in the treatment of various diseases including diabetes, malaria, abdominal pain and diarrhoea.

OBJECTIVE

To provide an overview of traditional medicinal claims, pharmacological properties, and phytochemical principles of P. kotschyi as a basis for its clinical applications and further research and development of new drugs.

METHODS

Through interpreting already published scientific manuscripts retrieved from different scientific search engines, namely, Medline, PubMed, EMBASE, Science Direct and Google scholar databases, an up-to-date review on the medicinal potentials of P. kotschyi from inception until September, 2020 was compiled. 'Pseudocedrela kotschyi', 'traditional uses', 'pharmacological properties' and 'chemical constituents' were used as search words.

RESULTS

At present, more than 30 chemical constituents have been isolated and identified from the root and stem bark of P. kotschyi, among which limonoids and triterpenes are the main active constituents. Based on prior research, P. kotschyi has been reported to possess anti-inflammatory, analgesic, antipyretic, anthelminthic, antimalaria, anti-leishmaniasis, anti-trypanosomiasis, hepatoprotective, antioxidant, antidiabetic, antidiarrheal, antimicrobial, and anticancer effects.

CONCLUSIONS

P. kotschyi is reported to be effective in treating a variety of diseases. Current phytochemical and pharmacological studies mainly focus on antimalaria, anti-leishmaniasis, anti-trypanosomiasis and anticancer potential of the root and stem bark of P. kotschyi. Although experimental data support the beneficial medicinal properties of this plant, there is still a paucity of information on its toxicity profile. Nonetheless, this review provides the basis for future research work.

A Novel Trimeric Triterpene From Chisocheton ceramicusMiq

A novel trimeric triterpene, bismoronic ceramicine (1), was isolated from the bark of Chisocheton ceramicus Miq. The structure was elucidated based on spectroscopic data and chemical correlations. Bismoronic ceramicine (1) showed moderate antimalarial activity against Plasmodium falciparum strain 3D7.

LC-MS Based Analysis and Biological Properties of Pseudocedrela kotschyi (Schweinf.) Harms Extracts: A Valuable Source of Antioxidant, Antifungal, and Antibacterial Compounds

The impact of two extraction solvents on the phenolic composition, antioxidant, and enzymes inhibitory and antimicrobial activities of two parts (leaves and stem bark) of P. kotschyi was studied. Two different LC-DAD-MSⁿ approaches were used to identify and quantify the bioactive compounds in the different extracts. A total of thirty-two compounds were quantified, being the procyanidin the most abundant in stem bark while catechin and flavonoids are most abundant in leaves. Overall, the stem bark extraction using methanol showed higher amounts of total phenolic (131.83 ± 1.81 mg GAE/g) and flavanol (14.14 ± 0.11 mg CE/g) while the leaves extraction using water exhibited stronger levels of total flavonoid (44.95 ± 0.38 mg RE/g) and phenolic acid (63.58 ± 2.00 mg CAE/g). As regards the antioxidant assays, methanol stem bark extracts were characterized by the highest antioxidant activities (DPPH: 1.94 ± 0.01 mmol TE/g, ABTS: 3.31 ± 0.01 mmol TE/g, FRAP: 2.86 ± 0.02 mmol TE/g, CUPRAC: 5.09 ± 0.08 mmol TE/g, phosphomolybdenum: 5.16 ± 0.23 mmol TE/g and metal chelating: 17.12 ± 0.46 mg EDTAE/g). In addition, the methanolic extracts of stem bark had highest impact on acetylcholinesterase (2.54 mg GALAE/g), butyrylcholinesterase (5.48 mg GALAE/g). In contrast, the methanolic extracts of leaves was potent against tyrosinase (77.39 ± 0.21 mg KAE/g) and α-glucosidase (0.97 ± 0.01 mmol ACAE/g), while a higher anti-α–amylase (0.97 ± 0.01 mmol ACAE/g) was observed for water extracts of the same part. All of the tested extracts showed inhibitory effects on elastase, except methanolic leaves extracts. Additionally, the extracts exhibited appreciable antifungal toward A. ochraceus, A. fumigatus, P. ochrochloron, T. viride, and P. funiculosum and promising antibacterial activity against M. flavus, S. aureus, L. monocytogenes, E. coli, P. aeruginosa, E. cloacae, and S. typhimurium. Taken together, the outcomes demonstrated P. kotschyi as a novel source of bioactive molecules of interest with an evident therapeutic value.

Diverse triterpene skeletons are derived from the expansion and divergent evolution of 2,3-oxidosqualene cyclases in plants

Triterpenoids are one of the largest groups of secondary metabolites and exhibit diverse structures, which are derived from C30 skeletons that are biosynthesized via the isoprenoid pathway by cyclization of 2,3-oxidosqualene. Triterpenoids have a wide range of biological activities, and are used in functional foods, drugs, and as industrial materials. Due to the low content levels in their native plants and limited feasibility and efficiency of chemical synthesis, heterologous biosynthesis of triterpenoids is the most promising strategy. Herein, we classified 121 triterpene alcohols/ketones according to their conformation and ring numbers, among which 51 skeletons have been experimentally characterized as the products of oxidosqualene cyclases (OSCs). Interestingly, 24 skeletons that have not been reported from nature source were generated by OSCs in heterologous expression. Comprehensive evolutionary analysis of the identified 152 OSCs from 75 species in 25 plant orders show that several pentacyclic triterpene synthases repeatedly originated in multiple plant lineages. Comparative analysis of OSC catalytic reaction revealed that stabilization of intermediate cations, steric hindrance, and conformation of active center amino acid residues are primary factors affecting triterpene formation. Optimization of OSC could be achieved by changing of side-chain orientations of key residues. Recently, methods, such as rationally design of pathways, regulation of metabolic flow, compartmentalization engineering, etc., were introduced in improving chassis for the biosynthesis of triterpenoids. We expect that extensive study of natural variation of large number of OSCs and catalytical mechanism will provide basis for production of high level of triterpenoids by application of synthetic biology strategies.

The Ethnobotany and Chemistry of South African Meliaceae: A Review

Meliaceae are widely distributed across the world in tropical or subtropical climates and are of considerable ethnobotanical importance as sources of traditional medicine and cosmetics. This comprehensive review summarizes the ethnobotanical uses and chemistry of 12 South African species, belonging to six genera: Ekebergia, Nymania, Entandrophragma, Pseudobersama, Trichilia, and Turraea. Eight of the species have ethnomedicinal records, classified into 17 major disease categories. The ethnomedicinal uses comprise 85 ailments dominated by gastrointestinal complaints, followed by gynaecological and obstetrics related problems. Chemical records were found for 10 species, which describe nine classes of compounds. In nearly all South African Meliaceae, limonoids are the predominant constituents while triterpenes, sterols, and coumarins are also common. The widest range of use-records and medicinal applications are found with the two most chemically diverse species, Ekebergiacapensis and Trichiliaemetica. Of the chemical compounds identified in the various plant organs of the 10 species of South African Meliaceae for which data are available, 42% was found in bark and 17% in seeds. Roots represent 35% and bark 33% of the organs that are used medicinally, and they are typically prepared as decoctions or infusions. Root and bark harvesting are destructive so that it may be important to examine the chemistry of plant parts such as wild-crafted leaves and fruits.

Limonoids with Diverse Oxidation Patterns of C-12 Indicating a Complete Ring C-seco Biogenetic Pathway from Munronia unifoliolata

Munrolins A-Q (1-17), 17 new ring C-seco limonoids with diverse oxidative patterns of C-12, together with nine known analogues (18-26), were isolated from the CH₂Cl₂ extract of Munronia unifoliolata. The planar structures were elucidated by a combination of 1D and 2D NMR and HR-MS analyses, while the absolute configurations were confirmed by ECD calculations and single-crystal X-ray diffraction. Munrolins A (1) and B (2) were first identified as ring C-seco limonoids with a 12,13-ether bridge moiety. Munrolins C-J (3-10) have a rare reduced primary alcohol fragment, while munrolin Q (17) has an unusual ketal fragment formed by dehydration of C-12/14. These limonoids with diverse alcohol and aldehyde type C11/12 branches may be generated through different degrees of reduction after the Baeyer-Villiger oxidation at the C ring, as key intermediates to supplement the biogenetic pathway of ring C-seco limonoids. Compounds 11, 19, and 26 could reverse the multidrug resistance of MCF-7/doxorubicin cells with reversal fold values of 5.2, 4.5, and 18.3, respectively.

Characterization and Antifungal Activity of Limonoid Constituents Isolated from Meliaceae Plants Melia dubia, Aphanamixis polystachya, and Swietenia macrophylla against Plant Pathogenic Fungi In Vitro

The plants of Meliaceae are native to tropical and subtropical regions as the Americas, west India, Southeast Asia, and Southern China. Many species of the genera Khaya, Swietenia, Aphanamixis, and Melia in this family are known as medicinal plants and have biological activities such as antiviral, antimicrobial, antifeeding, insecticidal, and cytotoxic properties. The objectives of this research are to characterize and evaluate the bioactive limonoids from several plants of Meliaceae against phytopathogenic fungi. During the search of antifungal compounds from the plants of Meliaceae, the three methanol extracts of Melia dubia, Aphanamixis polystachya, and Swietenia macrophylla were found to suppress the mycelial growth of several phytopathogenic fungi. Nine limonoids isolated from M. dubia (1–2), A. polystachya (3–5), and S. macrophylla (6–9) were evaluated, for the first time, their antifungal effectiveness against nine phytopathogenic fungi Fusarium oxysporum, Magnaporthe oryzae, Sclerotium rolfsii, Rhizoctonia solani, Alternaria spp., and Botrytis cinerea, and three oomycetes Phytophthora species. Limonoids 2, 3, 6, and 8 displayed a remarkable broad-spectrum antifungal activity against all the test fungi. Sclerotium rolfsii was highly sensitive to the four limonoids with IC50 values ranging from 79.4 to 128.0 µg/mL. Notably, chisocheton compound G (3) isolated from A. polystachya and khayanolide B (8) isolated from S. macrophylla were the most potent antifungal limonoids and exhibited a dose-dependent activity against Phytophthora species. Compounds 2 and 9 displayed moderate activity against M. oryzae. Our study results demonstrated the discovery of antifungal and lead compounds from the group of limonoids for application in the control of fungal plant diseases.

Structurally diverse limonoids and bio-active evaluation from Trichilia connaroides

Four new limonoids, named as trichiconlide G (1), 2-hydroxyltrijugin F (2), 23-oxo-21-hydroxyltrijugin F (3), 21-oxo-23-hydroxyltrijugin F (4), along with sixteen known analogues (5-20) were isolated from the leaves and twigs of Trichilia connaroides. Their structures and absolute configurations were determined by spectroscopic analyses, X-ray diffraction analysis, and TD-DFT-ECD calculations. Trichiconlide G (1) is one rare naturally occurring 1,2-seco phragmalin-type limonoid bearing a C-7/28 δ-lactone ring. Additionally, 2-hydroxyltrijugin F (2), 23-oxo-21-hydroxyltrijugin F (3), and 21-oxo-23-hydroxyltrijugin F (4) are three naturally occurring limonoids with a rare C-16/8 δ-lactone ring. All isolates were evaluated for their cytotoxic and anti-inflammatory activities. None of compounds exhibited cytotoxicity against five human cancer cell lines A-549, HepG2, 5-8F, Siha, and SCC-4 at the concentration of 40 μM. Compounds 16 and 17 showed moderate anti-inflammatory activity with IC₅₀ values of 28.45 ± 2.51 and 22.66 ± 2.01 μM, respectively.

Aglatestine A, a Rearranged Limonoid with a 3/6/6 Tricarbocyclic Framework from the Fruits of Aglaia edulis

Aglatestine A (1), an unprecedented 3/6/6 tricarbocyclic limonoid framework along with four biogenic A/D-seco limonoid analogues with rare β-substituents at C-6 (2-5), was discovered from the fruits of Aglaia edulis. The structures of 1-5 along with their absolute configurations were clarified using methods of HRMS(ESI), NMR, electronic circular dichroism, X-ray diffraction crystallography, and quantum chemical calculations. The plausible biogenetic speculation suggested that an electrophilic cyclization between C-1 carbocation from acetolysis and electron-rich C-5 from enolization of C═O of 2 may play a key role. The biological evaluation showed that 5 exhibited anti-inflammatory activity indicated by inhibiting NO release in LPS-activated RAW 264.7 macrophages (IC₅₀: 35.72 ± 1.96 μM).

Interaction of selected terpenoids with two SARS-CoV-2 key therapeutic targets: An in silico study through molecular docking and dynamics simulations

The outbreak of COVID-19 disease caused by SARS-CoV-2, along with the lack of targeted medicaments, forced the scientific world to search for new antiviral formulations. In the current emergent situation, drug repurposing of well-known traditional and/or approved drugs could be the most effective strategy. Herein, through computational approaches, we aimed to screen 14 natural compounds from limonoids and terpenoids class for their ability to inhibit the key therapeutic target proteins of SARS-CoV-2. Among these, some limonoids, namely deacetylnomilin, ichangin and nomilin, and the terpenoid β-amyrin provided good interaction energies with SARS-CoV-2 3CL hydrolase (Mpro) in molecular dynamic simulation. Interestingly, deacetylnomilin and ichangin showed direct interaction with the catalytic dyad of the enzyme so supporting their potential role in preventing SARS-CoV-2 replication and growth. On the contrary, despite the good affinity with the spike protein RBD site, all the selected phytochemicals lose contact with the amino acid residues over the course of 120ns-long molecular dynamics simulations therefore suggesting they scarcely can interfere in SARS-CoV-2 binding to the ACE2 receptor. The in silico analyses of docking score and binding energies, along with predicted pharmacokinetic profiles, indicate that these triterpenoids might have potential as inhibitors of SARS-CoV-2 Mpro, recommending further in vitro and in vivo investigations for a complete understanding and confirmation of their inhibitory potential.

Contributions of secondary alcohol-ketone O-H...O=C and furan-acetate Csp2-H...OOC synthons to the supramolecular packings of two bioactive molecules

The crystal structures of rubescin D (1, C₂₆H₃₀O₅) and monadelphin A (2, C₃₀H₃₆O₁₁), bioactive molecules of the vilasinin and gedunin classes of limonoids, respectively, are reported for the first time and the synthons affecting their crystal packings are analyzed on the basis of their occurrences in molecules in the Cambridge Structural Database that share the same moieties. Rubescin D, 1, crystallizes in the space group P2₁ and its molecular structure consists of three six-membered rings A, C and D having, respectively, envelope, twist-boat and half-chair conformations, and three five-membered rings with half-chair (B and E) and planar conformations (F). Many synthons found in the crystal packing of 1 are in agreement with expectations derived from molecules displaying the same moieties. However, the secondary alcohol-ketone O-H...O=C synthon, which has a low occurrence (2.9%), contributes much to the layered packing, while the furan-ketone Csp²-H...O=C and secondary alcohol-epoxide O-H...OC₂ synthons usually found in these compounds (occurrences of 20.6 and 17.6%, respectively) are missing. The packing of 1 is close to that of ceramicine B (3), but is completely different from that of TS3 (4), suggesting that the absence of the epoxide group in 3 would have favoured the furan-secondary alcohol Csp²-H...OH synthon and that the missing hydroxy group in 4, a strong hydrogen-bond donor, would have favoured the involvement of water molecules in the crystal packing. The molecular structure of monadelphin A, 2, consists of four six-membered fused rings (A, B, C and D) and one five-membered ring (E); they have twist-boat (A and C), chair (B), screw-boat (D) and planar (E) conformations. The molecule crystallizes in the space group P2₁2₁2₁ with the contribution of many synthons usually found in compounds having the same moieties. However, the secondary alcohol-acetate O-H...OOC and secondary alcohol-ketone O-H...O=C synthons (occurrences of 16.7% each in these compounds) are missing. The furan-acetate Csp²-H...OOC synthon not observed in these compounds greatly contributes to the layered packing of 2. The layered packing is very close to those of 7-oxogedunin (5) and 6-dehydro-7-deacetoxy-7-oxogedunin (6), which both crystallize in the space group P2₁.

Identification and quantification of markers in Azedarach Fructus and Toosendan Fructus

Toosendan Fructus with various pharmaceutical activities is a good source for the finding of new bioactive components, especially limonoids inside have been reported to have anticancer and antifeedant activities. To find more potential new bioactive compounds, the mass spectrometric characteristics of nimbolinin-type limonoids were first investigated. Utilizing these characteristics, totally 60 nimbolinins, including 33 new ones and at least 10 bioactive compounds, were identified by ultra-high performance liquid chromatography-quadrupole-time-of-flight mass spectrometry (UHPLC-Q-TOF/MS). Furthermore, based on UHPLC-Q-TOF/MS and statistical analysis, 9 limonoids were identified to be the differential components between Toosendan Fructus and Azedarach Fructus. Particularly, nimbolinin A and toosendanin (TSN) with higher content in Azedarach Fructus and Toosendan Fructus respectively should be good markers. Finally, an UHPLC-triple quadrupole mass spectrometry (UHPLC-QQQ/MS) quantification approach for nimbolinin A and TSN was developed for their quality control. These results provided the basis for drug development and quality control of Toosendan Fructus and Azedarach Fructus.

Trichilones A-E: New Limonoids from Trichilia adolfi

In addition to the trichilianones A-D recently reported from Trichilia adolfi, a continuing investigation of the chemical constituents of the ethanol extract of the bark of this medicinal plant yielded the five new limonoids 1-5. They are characterized by having four fused rings and are new examples of prieurianin-type limonoids, having a ε-lactone which in 4 and 5 is α, β- unsaturated. The structures of the isolated metabolites were determined by high field NMR spectroscopy and HR mass spectrometry. The new metabolites were shown to have the ε-lactone fused with a tetrahydrofuran ring which is connected to an oxidized hexane ring joined with a cyclo-pentanone having a 3-furanyl substituent. As the crude extract possesses antileishmanial activity, the compounds were assayed for cytotoxic and antiparasitic activities in vitro in murine macrophage cells (raw 264.7 cells) and in Leishmania amazoniensis as well as L. braziliensis promastigotes. Metabolites 1-3 and 5 showed moderate cytotoxicity (between 30-94 µg/mL) but are not responsible for the antileishmanial effect of the extract.

Construction of Pentacyclic Limonoid Skeletons via Radical Cascade Reactions

Limonoids 1 and 2 share a 6/6/6/5-membered ABCD-ring system and a six-membered oxacycle and differ in their C9-stereochemistries. A new radical-based strategy was devised to construct the pentacyclic skeletons of 1 and 2. An oxacycle-fused A-ring and enyne fragments were coupled to produce radical precursors 4a-4c with different C7-oxygen functionalities. The bridgehead tertiary bromide of 4a-4c participated in a radical cascade reaction with the three unsaturated bonds to cyclize the C9-diastereomeric BCD-rings.

MS diagnostic model and rapid distinguishing of bioactive limonoids in fruits of Melia toosendan using solid-phase extraction coupled with LC-MS/MS

INTRODUCTION

Melia toosendan Sieb. et Zucc. has been used as a Chinese folk medicine for roundworm treatment since ancient times. Many diverse limonoids have been isolated from Meliaceae plants, but it remains difficult to isolate and identify other limonoids because of their small natural concentrations.

OBJECTIVE

This study was performed to overcome the difficulties associated with fast and accurate identification of limonoids and establish a reliable and sensitive method for the analysis of minor limonoids in M. toosendan fruits.

METHODS

An efficient strategy for enrichment, detection, and identification of minor limonoids from M. toosendan fruits using solid-phase extraction with high-performance liquid chromatography-quadrupole time-of-flight tandem mass spectrometry (SPE-HPLC-Q-TOF-MS/MS) was developed herein.

RESULTS

Characteristic fragmentations and fragmentation ions containing trichilin-, nimbin-, and vilasinin-class limonoid skeletons were initially studied, and characteristic diagnostic ions involved retro Diels-Alder (RDA) reactions or homolytic cleavages, which were used to identify minor limonoids. In total, 13 limonoids, including four new ones, were identified.

CONCLUSION

This is the first report on the analysis of M. toosendan fruits to identify limonoids. This novel analysis method may stimulate further research regarding the identification of limonoids in other plant species.

Rapid identification, isolation, and evaluation on anti-neuroinflammatory activity of limonoids derivatives from the root bark of Dictamnus dasycarpus

A total of 49 limonoids derivatives were rapidly identified by UNIFI software and three new limonoids derivatives, named dasycarinone (1, DAS), isodictamdiol C (2) and dasycarinone A (3), along with nineteen known compounds, were isolated from the root bark of Dictamnus dasycarpus, named as "Baixianpi" in Chinese. Their structures were elucidated on the basis of spectroscopic data (UV, IR, HR-ESI-MS, NMR, CD spectra and OR). All the compounds were tested for anti-inflammatory activities by suppressing the nitric oxide (NO) production in lipopolysaccharide (LPS) induced BV-2 cells. DAS exhibited a strong anti-inflammatory activity with IC₅₀ value of 1.8 μM. Nuclear Factor kappa B (NF-κB) luciferase assay and enzyme-linked immune sorbent assay indicated that DAS can suppress the release of inflammatory cytokines such as Tumor Necrosis Factor α (TNF-α), interleukin 6 (IL-6) via inactivating NF-κB signaling pathways. Moreover, we found that anti-inflammatory activities of obacunone-class are better than those of limonin-class by analyzing structure-activity relationship. Our results suggested that obacunone derivatives play an important role on anti-inflammation of Baixianpi. As a representative among them, DAS showed a strong anti-inflammatory activity via suppressing NF-κB signaling pathways.

Recent Advances in the Use of the Dimerization Strategy as a Means to Increase the Biological Potential of Natural or Synthetic Molecules

The design of C₂-symmetric biologically active molecules is a subject of interest to the scientific community. It provides the possibility of discovering medicine with higher biological potential than the parent drugs. Such molecules are generally produced by classic chemistry, considering the shortness of reaction sequence and the efficacy for each step. This review describes and analyzes recent advances in the field and emphasizes selected C₂-symmetric molecules (or axial symmetric molecules) made during the last 10 years. However, the description of the dimers is contextualized by prior work allowing its development, and they are categorized by their structure and/or by their properties. Hence, this review presents dimers composed of steroids, sugars, and nucleosides; known and synthetic anticancer agents; polyphenol compounds; terpenes, known and synthetic antibacterial agents; and natural products. A special focus on the anticancer potential of the dimers transpires throughout the review, notwithstanding their structure and/or primary biological properties.

Limonoid biosynthesis 3: Functional characterization of crucial genes involved in neem limonoid biosynthesis

Neem (Azadirachta indica L.) is well known for its medicinal, agricultural, and pesticidal applications since ages. The secondary metabolites, limonoids, confer these biological properties, wherein over 150 different limonoids have been reported from neem. To understand limonoid biosynthesis, we analyzed tissue-specific (kernel, pericarp, leaves, and flower) transcriptome that resulted in the identification of one farnesyl diphosphate synthase (AiFDS), one squalene synthase (AiSQS), three squalene epoxidases (AiSQE1, AiSQE2, and AiSQE3), two triterpene synthases (AiTTS1 and AiTTS2), cycloartenol synthase (AiCAS), two cytochrome P450 reductases, and ten cytochrome P450 systems. Comparative tissue-expression analysis indicated that AiFDS, AiSQS, AiSQE3, and AiTTS1 are expressed higher in the kernel than in the other tissues. Heterologously expressed recombinant AiTTS1 produced tirucalla-7,24-dien-3β-ol as the sole product. Expression profile data, phylogeny with triterpene synthases from Meliaceae and Rutaceae families, real-time PCR of different tissues, and transient transformation revealed the involvement of tirucalla-7,24-dien-3β-ol synthase (AiTTS1) in limonoid biosynthesis. Further, mutagenesis studies of AiTTS1 indicated that Y125 and F260 are probably involved in stabilization of dammarenyl cation. A 2.6-fold increase in production of tirucalla-7,24-dien-3β-ol was observed when AiSQE1 was co-expressed with mutant AiTTS1 in a yeast system. Furthermore, we functionally characterized the highly expressed cytochrome P450 reductases and cycloartenol synthase. This study helps in further analysis and identification of genes involved in limonoid biosynthesis in Meliaceae/Rutaceae and their production in a metabolically tractable heterologous system.

Limonoids from Guarea guidonia and Cedrela odorata: Heat Shock Protein 90 (Hsp90) Modulator Properties of Chisomicine D

Nine new limonoids (1-9) were isolated from the stem bark of Guarea guidonia (1-4) and Cedrela odorata (5-9). Their structures were elucidated using 1D and 2D NMR and MS data and chemical methods as three A2,B,D-seco-type limonoids (1-3), a mexicanolide (4), three nomilin-type (5-7) limonoids, and two limonol derivatives (8 and 9). A DFT/NMR procedure was used to define the relative configurations of 1 and 3. A surface plasmon resonance approach was used to screen the Hsp90 binding capability of the limonoids, and the A2,B,D-seco-type limonoid 8-hydro-(8S*,9S*)-dihydroxy-14,15-en-chisomicine A, named chisomicine D (1), demonstrated the highest affinity. By means of mass spectrometry data, biochemical and cellular assays, and molecular docking, 1 was found as a type of client-selective Hsp90 inhibitor binding to the C-terminus domain of the chaperone.

New limonoids and quinolone alkaloids with cytotoxic and anti-platelet aggregation activities from Evodia rutaecarpa (Juss.) Benth

One new limonoid, named 19-hydroxy methyl isoobacunoate diosphenol (1); one new degraded limonoid, named 9α-methoxyl dictamdiol (9); two new quinolone alkaloids, 1-methyl-3-[(7E,9E,12Z)-7,9,12-pentadecadienyl]-4(1H)-quinolone (11) and 1-methyl-3-[(7E,9E,11E)-7,9,11-pentadecadienyl]-4(1H)-quinolone (12), along with eight known compounds, evodol (2), 7β-acetoxy-5-epilimonin (3), rutaevine (4), 6β-acetoxy-5-epilimonin (5), limonin (6), obacunone (7), clauemargine L (8), hiiranlactone E (10) were isolated from the fruits of Evodia rutaecarpa (Juss.) Benth.. Structures of the four new compounds were elucidated on the basis of extensive spectroscopic techniques, including 1D and 2D NMR techniques. Compounds 3, 5, 9, 11 and 12 showed obviously cytotoxic activity against six human tumor lines, while compounds 11, 12 displayed anti-platelet aggregation induced by ADP at 50 μM and 100 μM.

Trichilianones A-D, Novel Cyclopropane-Type Limonoids from Trichilia adolfi

The fractionation of an ethanol extract of the bark of Trichilia adolfi yielded four novel limonoids (trichilinones A-D, 1-4), with five fused rings and related to the hortiolide-type limonoids. Starting with an ε-lactone, which is α,β-unsaturated in trichilinones A and D (1 and 4), attached to a tetrahydrofuran ring that is connected to an unusual bicyclo [5.1.0] hexane system, joined with a cyclopentanone with a 3-furanyl substituent [(2-oxo)-furan-(5H)-3-yl in trichilinone D (4)], the four compounds isolated display a new 7/5/3/5/5 limonoid ring system. Their structures were established based on extensive analysis of NMR spectroscopic data. As the crude extract possessed anti-leishmanial properties, the compounds were assayed for cytotoxic and anti-parasitic activities in vitro in murine macrophages cells (Raw 264.7) and leishmania promastigotes (L. amazoniensis and L. braziliensis), respectively. The compounds showed moderate cytotoxicity (approximately 70 μg/mL), but are not responsible for the leishmanicidal effect of the extract.

Limonoids and other triterpenoids from Entandrophragma angolense

Four new compounds (1-4) were isolated from the stem bark of Entandrophragma angolense along with eleven known structures (5-15). The chemical structures were elucidated on the basis of spectroscopic and HRMS data, and the absolute configuration was established with the aid of electronic circular dichroism. Compound 5 displayed moderate cytotoxicity against MDA-MB-231, OVCAR3, MDA-MB-435, and HT29 cell lines, with IC₅₀ values ranging from 2.0-5.9 μM.

seco-Labdanes: A Study of Terpenoid Structural Diversity Resulting from Biosynthetic C-C Bond Cleavage

The cleavage of a C-C bond is a complexity generating process, which complements oxidation and cyclisation events in the biosynthesis of terpenoids. This process leads to increased structural diversity in a cluster of related secondary metabolites by modification of the parent carbocyclic core. In this review, we highlight the diversifying effect of C-C bond cleavage by examining the literature related to seco-labdanes-a class of diterpenoids arising from such C-C bond cleavage events.

Krishnolides E-K: New limonoids from the Krishna mangrove Xylocarpus moluccensis

Seven new limonoids, named krishnolides E-K (1-7), including three khayanolides, two mexicanolides, a derivative of trangmolin A, and an andirobin, were isolated from seeds of the Indian Krishna mangrove, Xylocarpus moluccensis. The structures of these limonoids were established by HRESIMS, extensive NMR investigations, and X-ray crystallography. Most notably, the absolute configurations of 1, 5, 6, and 7 were unequivocally determined by single-crystal X-ray diffraction analyses (Cu Kα). Krishnolide F (2) exhibited significant agonistic effects on human pregnane-X-receptor (hPXR) at the concentration of 10.0 μM. Molecular docking revealed that 2 could bind a helix near the region of the Helix 12 of hPXR. Polar contribution could be electrostatic effects from the formation of two stable protein-ligand hydrogen bonds between Gln285/1-OH and His407/1-OH, respectively. This is the first report of agonistic effects of a khayanolide-type limonoid on hPXR.

Diverse prieurianin-type limonoids with oxygen-bridged caged skeletons from two Aphanamixis species: discovery and biomimetic conversion

The formation of HO-1 based oxygen-bridges and new C–C bonds via a Dieckmann reaction provided diverse ring systems, aphanamolide-type skeletons, and a solution for the structural elucidation of prieurianin limonoids with missing NMR signals.

Three phragmalin-type limonoids orthoesters and the structure of odoratone isolated from the bark of Entandrophragma candollei (Meliaceae)

The phytochemical exploration of the Entandrophragma candollei stem bark extract led to the isolation and identification of twenty compounds including three undescribed phragmalin-class limonoids named encandollens C-E (1-3), the undescribed protolimonoid 5 together with sixteen known compounds. The structures of all the isolated compounds were determined by interpretation of their spectroscopic and spectrometric data including HRMS, 1D and 2D NMR analyses. The assignment of the absolute and relative stereochemistry of the undescribed compounds was achieved using SC-XRD analyses as well as NOESY experiments. The previously reported structure of odoratone (5a) was corrected as 23 R,24 S-dihydroxy-22 S,25-epoxytirucall-7-en-3-one (5) based on its NMR and SC-XRD data. Prieurianin (4) exhibited high cytotoxic activity on KB3-1 cell lines with an IC₅₀ of 1.47 μM compared to the reference griseofulvin (IC₅₀ = 17-21 μM). The results of the in silico docking of compound 4 supported and delivered further insights on its cytotoxicity.

Bioactive Limonoids and Triterpenoids from the Fruits of Melia azedarach

Nine new limonoids, meliazedarines A-I (1-9), seven known analogues (10-16), and five known triterpenoids (17-21) were isolated from the fruits of Melia azedarach. Their structures were determined by analysis of 1D and 2D NMR, HRESIMS, X-ray diffraction, and electronic circular dichroism (ECD) data. Compound 7 showed significant cytotoxicity against the HCT116 cell line with IC₅₀ values of 0.3 ± 0.1 μM.

Characterization of a 2,3-oxidosqualene cyclase in the toosendanin biosynthetic pathway of Melia toosendan

Toosendanin, bearing a furan ring, is a limonoid belonging to the group of tetranortriterpenoids. Toosendanin is a phytochemical found in the medicinal plant Melia toosendan Sieb. et Zucc. of the Meliaceae family. Toosendanin and its derivatives demonstrate high insecticidal activity and are important pesticides derived from plants. Despite intensive investigation of limonoids over several decades, the biosynthetic pathway of these triterpenoids is less understood. To identify the key enzymes involved in the toosendanin biosynthetic pathway, we analyzed the contents of toosendanin in various plant tissues and parts and found that the highest level of toosendanin was found in the developing fruit and gradually decreased as the fruit matured. More than 346 116 transcripts were assembled based on 394 million paired-end Illumina reads and 6 million PacBio reads from the pooled RNA samples of fruits, leaves and young barks. A total of 186 263 genes were predicted. Six 2,3-oxidosqualene cyclase (OSC) genes were identified by analyzing the association between gene expression and metabolite profiles. Functional analyses using the Nicotiana benthamiana transient expression assay showed that MtOSC1 catalyzed 2,3-oxidosqualene to produce a tetracyclic triterpene skeleton, tirucalla-7,24-dien-3β-ol, which is predicted as the precursor for toosendanin biosynthesis. We identified another OSC, MtOSC6, which is a lupeol synthase. Using synthetic biology methods, these identified enzymes could be used to model a biosynthetic pathway to produce large quantities of toosendanin.

Carapanins A-C: new limonoids from andiroba (Carapa guianensis) fruit oil

Carapanins A-C (1-3) were isolated from the fruit oil of Carapa guianensis. Compounds 1 and 2 are limonoids with unique structures. Namely, compound 1 is an andirobin-type limonoid with a C-15/C-30 γ-lactone instead of the δ-lactone of the D-ring, and compound 2 is a mexicanolide-type limonoid with a C-16/C-30 δ-lactone ring. The absolute structures of 1 and 2 were determined using X-ray crystallography, whereas the structure of 3 was established mainly via NMR and mass spectroscopy. The inhibitory effects of 1-3 on nitric oxide production were evaluated, and it was revealed that 2 and 3 were potent nitric oxide inhibitors.

Chemical Compounds and Biologic Activities: A Review of Cedrela Genus

The genus Cedrela P. Browne, which belongs to the Meliaceae family, has eighteen species. Trees of this genus are of economic interest due to wood quality, as well as being the focus of studies because of relevant biologic activities as in other Meliaceae species. These activities are mainly related to limonoids, a characteristic class of compounds in this family. Therefore, the aim of this review is to perform a survey of the citations in the literature on the Cedrela genus species. Articles were found on quantitative and qualitative phytochemical studies of the Cedrela species, revealing the chemical compounds identified, such as aliphatics acid and alcohol, flavonoids, tocopherol, monoterpenes, sesquiterpenes, triterpenes, cycloartanes, steroids, and limonoids. Although some activities were tested, the majority of studies focused on the insecticidal, antifeedant, or insect growth inhibitor activities of this genus. Nonetheless, the most promising activities were related to their antimalarial and antitripanocidal effects, although further investigations are still needed.