Chemistry and biological activity of polyisoprenylated benzophenone derivatives

13C NMR dereplication-assisted isolation of bioactive polyphenolic metabolites from Clusia flava Jacq

Presently it is estimated that many of the approximately 4000 new natural products isolated every year following complicated, long, and expensive isolation processes are already known; because of this, developing new strategies for locating secondary metabolites of interest in complex extracts or fractions is important. Currently, chromatographic and spectroscopic techniques are being used to optimize the isolation and identification of natural products. In this investigation we have used 13C NMR dereplication analyses for the quick identification of a number of triterpenes (friedelin, lupeol, betulinic acid), sterols (euphol, β-sitosterol) and fatty acids (palmitic acid) present in semipurified fractions obtained from the stem bark extract of Clusia flava and to assist in the isolation of the bioactive metabolites trapezifolixanthone and paralycolin A. The complete and correct assignment of the 1H and 13C NMR spectroscopic data for paralycolin A is reported for the first time and the antioxidant and antiAGEs activity of both metabolites is described.

Lewis Acid-Catalyzed Benzannulation of Vinyloxiranes with 3-Formylchromones or 1,4-Quinones for Diversely Functionalized 2-Hydroxybenzophenones, 1,4-Naphthoquinones, and Anthraquinones

A facile and convenient protocol for the regioselective construction of functionalized 2-hydroxybenzophenones is described. This protocol involves the Sc(OTf)3/BF3·OEt2-catalyzed benzannulation of 2-vinyloxirans with 3-formylchromone, which involves cascade in situ diene formation, [4 + 2] cycloaddition, elimination, and ring-opening strategies. Moreover, it provides an expedited synthetic pathway to access biologically intriguing 1,4-naphthoquinones and anthraquinones including vitamin K3 and tectoquinone. The synthesized compounds also hold potential for use as UV filters and show promise as chemosensors for Cu2+ and Mg2+ ions.

Synthesis of new bis(dimethylamino)benzophenone hydrazone for diabetic management: In-vitro and in-silico approach

Inhibiting α-glucosidase is a reliable method for reducing blood sugar levels in diabetic individuals. Bis(dimethylamino)benzophenone derivatives 1-27 were synthesized from bis(dimethylamino)benzophenone via two-step reaction. Different spectroscopic techniques, including EI-MS and 1H NMR, were employed to characterize all synthetic derivatives. The elemental composition of synthetic compounds was confirmed by elemental analysis and results were found in agreement with the calculated values. The synthetic compounds 1-27 were evaluated for α-glucosidase inhibitory activity, except five compounds all derivatives showed good to moderate inhibitory potential in the range of IC50 = 0.28 ± 2.65 - 0.94 ± 2.20 μM. Among them, the most active compounds were 5, 8, 9, and 12 with IC50 values of 0.29 ± 4.63, 0.29 ± 0.93, 0.28 ± 3.65, and 0.28 ± 2.65, respectively. Furthermore, all these compounds were found to be non-toxic on human fibroblast cell lines (BJ cell lines). Kinetics study of compounds 8 and 9 revealed competitive type of inhibition with Ki values 2.79 ± 0.011 and 3.64 ± 0.012 μM, respectively. The binding interactions of synthetic compounds were also confirmed through molecular docking studies that indicated that compounds fit well in the active site of enzyme. Furthermore, a total of 30ns MD simulation was carried out for the most potent complexes of the series. The molecular dynamics study revealed that compound-8 and compound-12 were stable during the MD simulation.

Benzophenones-natural metabolites with great Hopes in drug discovery: structures, occurrence, bioactivities, and biosynthesis

Fungi have protruded with enormous development in the repository of drug discovery, making them some of the most attractive sources for the synthesis of bio-significant and structural novel metabolites. Benzophenones are structurally unique metabolites with phenol/carbonyl/phenol frameworks, that are separated from microbial and plant sources. They have drawn considerable interest from researchers due to their versatile building blocks and diversified bio-activities. The current work aimed to highlight the reported data on fungal benzophenones, including their structures, occurrence, and bioactivities in the period from 1963 to April 2023. Overall, 147 benzophenones derived from fungal source were listed in this work. Structure activity relationships of the benzophenones derivatives have been discussed. Also, in this review, a brief insight into their biosynthetic routes was presented. This work could shed light on the future research of benzophenones.

Recent advances on Pestalotiopsis genus: chemistry, biological activities, structure-activity relationship, and biosynthesis

Strains of the fungal genus Pestalotiopsis are reported as large promising sources of structurally varied biologically active metabolites. Many bioactive secondary metabolites with diverse structural features have been derived from Pestalotiopsis. Moreover, some of these compounds can potentially be developed into lead compounds. Herein, we have systematically reviewed the chemical constituents and bioactivities of the fungal genus Pestalotiopsis, covering a period ranging from January 2016 to December 2022. As many as 307 compounds, including terpenoids, coumarins, lactones, polyketides, and alkaloids, were isolated during this period. Furthermore, for the benefit of readers, the biosynthesis and potential medicinal value of these new compounds are also discussed in this review. Finally, the perspectives and directions for future research and the potential applications of the new compounds are summarized in various tables.

A review of nemorosone: Chemistry and biological properties

Nemorosone is a bicyclic polyprenylated acylphloroglucinol derivative originally isolated from Clusia spp. and it can be obtained through chemical synthesis employing different synthetic strategies. Since its discovery, it has attracted great attention both from a biological and chemical viewpoint. In the present article, we attempted to review various chemical and biological topics around nemorosone, with an emphasis on its antiproliferative activities. For this purpose, relevant data was collected from different scientific databases including Google Scholar, PubMed, Scopus and ISI Web of Knowledge. This natural compound has shown activity against several types of malignancies such as leukemia, human colorectal, pancreatic, and breast cancer because it modulates multiple molecular pathways. Nemorosone has both cytostatic and cytotoxic activity and it also seems to induce apoptosis and ferroptosis. Additionally, it has antimicrobial capabilities against Gram-positive bacteria and parasites belonging to genus Leishmania. Its promising antiproliferative pre-clinical effects deserve further attention for anticancer and anti-parasitic drug development and translation to the clinic.

Sc(OTf)3/BF3·OEt2-Catalyzed Annulation of 3-Formylchromones with Functionalized Alkenes: Access to Diverse 2-Hydroxybenzophenones

The Sc(OTf)₃/BF₃·OEt₂-catalyzed annulation of 3-formylchromones with functionalized alkenes for the direct construction of 2-hydroxybenzophenones is described. Sc(OTf)₃/BF₃·OEt₂ acts as a synergistic catalyst, providing rapid synthetic access to diversely and highly functionalized 2-hydroxybenzophenones. This reaction has excellent regio- and chemoselectivities and is suitable for late-stage functionalization. The reaction proceeds via [3 + 3] and [4 + 2] cycloaddition processes, through carbonyl-ene, Diels-Alder, or aldol-type reactions. Furthermore, this protocol tolerates the various functional groups present in natural terpenes and steroids.

The ethnobotanical relevance of the tribe Symphonieae (Clusiaceae) around the world

ETHNOPHARMACOLOGICAL RELEVANCE

The tribe Symphonieae (Clusiaceae) encompasses 48 species accommodated in seven genera (Lorostemon, Montrouziera, Moronobea, Pentadesma, Platonia, Symphonia and Thysanostemon). Parts of these plants, mainly the exudates and the seeds oil are useful for different purposes, especially for treating dermatological conditions. In addition to the role in the folk medicine, some species are of great economic and cultural importance for native people from different continents.

AIM OF THE REVIEW

The goal of this review is to critically summarize the current knowledge on systematics, ethnobotanical, chemical and pharmacological aspects of species from the tribe Symphonieae, as well as to provide support for future taxonomic and phylogenetic studies on the Clusiaceae family.

MATERIALS AND METHODS

The available information was gathered from many different databases (Web of Science, ScienceDirect, Scopus, Pubmed, ChemSpider, SciFinder, ACS Publications, Wiley Online Library, Useful Tropical Plants Database, Google Scholar). Additional data from books, theses and dissertations were also included in this review.

RESULTS

Chemical studies of Symphonieae have demonstrated that the genera are a source of benzophenones, xanthones and biflavonoids. Components as sesquiterpenoids, triterpenoids, flavonoids, free fatty acids, among others, have also been reported. Extracts and compounds isolated from a variety of species have been exhibiting antimicrobial, cytotoxic and antiprotozoal activities, corroborating part of their medicinal uses. In addition, certain species produce edible fruits and a kind of "butter" with economic importance. All species produce exudate, which often has great relevance in the daily lives of local people.

CONCLUSION

Several species of Symphonieae have potential therapeutic applications and some of them have been investigated to scientifically validate their popular uses. In addition, a number of species have proved to be a rich source of promising pharmacologically active compounds. Finally, the value of fruits, exudate and butter, for instance, should serve as a stimulus for the sustainable development of products that aim to take advantage of these natural resources.

Antimicrobial activity of polyphenolic compounds from Spirulina against food-borne bacterial pathogens

Food-borne drug-resistant bacteria have adverse impacts on both food manufacturers and consumers. Disillusionment with the efficacy of current preservatives and antibiotics for controlling food-borne pathogens, especially drug-resistant bacteria, has led to a search for safer alternatives from natural sources. Spirulina have been recognized as a food supplement, natural colorant, and enriched source of bioactive secondary metabolites. The main objectives of this study were to isolate polyphenolic compounds from Spirulina and analyze their antibacterial potential against drug-resistant food-borne bacterial pathogens. We found that fraction B of methanol extract contained a high quantity of polyphenols exhibiting broad spectrum antimicrobial effects against drug-resistant food-borne bacterial pathogens. Potential secondary metabolites, such as benzophenone, dihydro-methyl-phenylacridine, carbanilic acid, dinitrobenzoate, propanediamine, isoquinoline, piperidin, oxazolidin, and pyrrolidine, were identified by gas chromatography and mass spectrophotometry (GCMS). These metabolites are active against both gram-positive and gram-negative pathogens. Our work suggests that phenolic compounds from Spirulina provide a natural and sustainable source of food preservatives for future use.

Structure of Leaf Galls in Clusia fluminensis Planch and Triana (Clusiaceae): Sex-Biased Development in a Dioecious Host Plant

Galls are remarkable parasite–plant interactions that develop in different organs. They are induced by various organisms which manipulate or reprogram plant development. Galls in dioecious species and their effects on the host plant are seldom described in the literature. This paper presents a novel study of galls in a dioecious plant of the neotropical region. Our study aimed to analyze gall development and describe morphological and metabolic changes in galled leaves caused by Cecidomyiidae (Diptera) in Clusia fluminensis (Clusiaceae), a dioecious plant from Brazilian restinga. We investigated male and female individuals to detect different responses and sex-biased interactions. The non-galled leaves of female and male individuals of C. fluminensis exhibited similar anatomical structures. Nevertheless, galls developed only in male individuals. The activity of the Cecidomyiidae led to several morphological and anatomical changes, such as the hypertrophy of the leaf blade, especially the chlorenchyma. Our results indicated an interesting exception for the pattern of storage of lipids and starch in Cecidomyiidae galls, and sex-biased development in a dioecious plant, with the variation of metabolic compounds, especially phenolics and flavonoids, which may inhibit gall development in female individuals.

In vitro protective effect of topical nanoemulgels containing Brazilian red propolis benzophenones against UV-induced skin damage

The overexposure of the skin to ultraviolet (UV) radiation may lead to oxidative stress, resulting in severe damage. The prevention of skin injuries through the topical application of natural compounds rich in antioxidants, such as propolis extracts, has shown promising results. In Brazil, the "red propolis" extract has stood out due to its complex constitution, based mainly on polyprenylated benzophenones (BZP). However, although the use of red propolis extracts has been shown to be encouraging, their addition in topical formulations is limited by the low solubility of BZP. For this reason, this study aimed to develop topical nanoemulgels containing Brazilian red propolis (BRP) extract to increase the potential of topical application, and the evaluation of skin protection against UVA/UVB radiation damage by means of protein carbonylation, protein thiol content and TBARS assays. The nanoemulgels were obtained by adding gelling polymer to nanoemulsions that were previously prepared by spontaneous emulsification. In this sense, a nanoemulgel containing BRP extract-loaded nanoemulsions (H-NE) and a nanoemulgel containing BRP extract-loaded nanoemulsions with DOTAP (H-NE/DT) were prepared. The physicochemical characterization of nanoemulgels showed monodisperse populations of 200-300 nm. The H-NE zeta potential was -38 mV, while that of H-NE/DT was +36 mV. BZP content in the formulations was around 0.86 mg g-1. These parameters remained stable for 90 days under cold storage. H/NE and H-NE/DT presented a non-Newtonian pseudoplastic rheological behavior. Permeation/retention studies, through porcine ear skin, showed the highest BZP retention (18.11 μg cm-2 after 8 h) for H-NE/DT, which also demonstrated, in an in vitro study, the highest ability to protect skin against oxidative damage after UVA/UVB radiation exposure. The results concerning the antioxidant activity revealed that formulations containing the BRP n-hexane extract were the most promising in combating oxidative stress, probable due to the presence of polyprenylated BZP. Altogether, the outcomes of this study suggest that nanoemulgels have suitable characteristics for topical application, and may be an alternative for the prevention of oxidative skin damage caused by UVA/UVB radiation.

A new benzophenone with biological activities purified from Aspergillus fumigatus SWZ01

Strain SZW01 was isolated from sea sediment collected from Shenzhen in Guangdong province, China, and was later identified as Aspergillus fumigatus by16S rDNA sequence analysis. Various chromatographic processes led to the isolation and purification of three compounds from the fermentation culture of SZW01, including a new compound, 2,6'-dihydroxy-2,4'dimethoxy-8'-methyl-6-methoxy-acyl-ethyl-diphenylmethanone (1), and two known compounds: fumigaclavine C (2) and alternarosin A (3), as characterised by UV, IR, 1 D, 2 D-NMR and MS data. The antioxidant and α-glucosidase inhibitory activities of these compounds were evaluated. The result illustrated that compound 1 exhibited a moderate antioxidant activity and stronger α-glucosidase inhibitory activity than acarbose.

A New Polycyclic Polyprenylated Acylphloroglucinol Derivative from Garcinia verrucosa

In our continuing phytochemical screening program aimed at finding major constituents of endemic Madagascar plants as potential templates for semisynthesis, we investigated the ethyl acetate extract of stem bark of Garcinia verrucosa. Fractionation of the extract led to the isolation of the major compound named garcicosin. Its structure was elucidated by spectroscopic methods including 1D and 2D homo- and heteronuclear NMR techniques (COSY, HSQC, HMBC and NOESY), and HR-mass spectrometry.

Total Synthesis of (-)-Nemorosone and (+)-Secohyperforin

A general strategy for the synthesis of polycyclic polyprenylated acylphloroglucinols is described in which a scalable, Lewis acid catalyzed epoxide-opening cascade cyclization is used to furnish common intermediate 4. The utility of this approach is exemplified by the total syntheses of both ent-nemorosone and (+)-secohyperforin, which were each accomplished in four steps from this intermediate.

Prenylated benzophenones from Triadenum japonicum

Six new prenylated benzophenones, (-)-nemorosonol (1) and trijapins A-E (2-6), were isolated from the aerial parts of Triadenum japonicum. (-)-Nemorosonol (1) and trijapins A-C (2-4) have a common tricyclo[4.3.1.0(3,7)]decane skeleton, while 1 is an enantiomer of (+)-nemorosonol previously isolated from Clusia nemorosa. The absolute configuration of (-)-nemorosonol (1) was assigned by ECD spectroscopy. Trijapins A-C (2-4) are analogues of 1 possessing an additional tetrahydrofuran ring. Trijapins D (5) and E (6) are prenylated benzophenones with a 1,2-dioxane moiety and a hydroperoxy group, respectively. (-)-Nemorosonol (1) exhibited antimicrobial activity against Escherichia coli (MIC, 8 μg/mL), Staphylococcus aureus (MIC, 16 μg/mL), Bacillus subtilis (MIC, 16 μg/mL), Micrococcus luteus (MIC, 32 μg/mL), Aspergillus niger (IC50, 16 μg/mL), Trichophyton mentagrophytes (IC50, 8 μg/mL), and Candida albicans (IC50, 32 μg/mL), while trijapin D (5) showed antimicrobial activity against C. albicans (IC50, 8 μg/mL).

Structural diversity and bioactivities of natural benzophenones

Natural benzophenones are a class of compounds with more than 300 members, mainly in the Clusiaceae family. We review key benzophenones, and provide an in-depth discussion of their great structural diversity and biological activity.

Isogarcinol is a new immunosuppressant

Calcineurin (CN), a unique protein phosphatase, plays an important role in immune regulation. In this study we used CN as a target enzyme to investigate the immunosuppressive properties of a series of natural compounds from Garcinia mangostana L., and discovered an active compound, isogarcinol. Enzymatic assays showed that isogarcinol inhibited CN in a dose-dependent manner. At concentrations resulting in relatively low cytotoxicity isogarcinol significantly inhibited proliferation of murine spleen T-lymphocytes induced by concanavalin A (ConA) and the mixed lymphocyte reaction (MLR). In addition, it performed much better in acute toxicity tests and via oral administration in mice than cyclosporin A (CsA), with few adverse reactions and low toxicity in experimental animals. Oral administration of isogarcinol in mice resulted in a dose-dependent decrease in delayed type hypersensitivity (DTH) and prolonged graft survival in allogeneic skin transplantation. These findings suggest that isogarcinol could serve as a new oral immunomodulatory drug for preventing transplant rejection, and for long-term medication in autoimmune diseases.

Cuban and Brazilian red propolis: botanical origin and comparative analysis by high-performance liquid chromatography-photodiode array detection/electrospray ionization tandem mass spectrometry

Chemical composition of propolis depends on the specificity of the local flora at the site of collection and thus on the geographic and climatic characteristics of this place. This paper describes a comparative analysis of Cuban red propolis (CRP), Brazilian red propolis (BRP), and Dalbergia ecastophyllum exudates (DEE) by high-performance liquid chromatography with diode-array detection and tandem mass spectrometry. The aim of this study was to investigate the overall chemical profile and the botanical origin of red propolis and to suggest similarities and differences between samples collected in different tropical regions. Isoliquiritigenin (1), liquiritigenin and naringenin (2 and 17), isoflavones (3-4 and 16), isoflavans (5-7 and 18), and pterocarpans (8-13) were detected in CRP, BRP, and DEE, whereas polyisoprenylated benzophenones (PPBs) guttiferone E/xanthochymol (14a,b) and oblongifolin A (15) were detected only in BRP. Pigments responsible for the red color of DEE and red propolis were also identified as two C30 isoflavans, the new retusapurpurin B (19) and retusapurpurin A (20). PPBs and pigments were isolated and unambiguously characterized by 1D and 2D NMR analysis. These results show that red propolis samples from different tropical zones have a similar chemical composition. DEE is the main red propolis source, but the presence of PPBs in BRP suggests the contribution of different botanical sources for Brazilian samples. This chemical information is important for quality control of red propolis and its commercial products and for biological study.

Fragmentation pathways of polycyclic polyisoprenylated benzophenones and degradation profile of nemorosone by multiple-stage tandem mass spectrometry

Nemorosone is a polycyclic polyisoprenylated benzophenone (PPBs) with strong cytotoxic activity. It is the major constituent of Clusia rosea floral resin and brown Cuban propolis. Other PPBs found in Cuban propolis are oxidized and cyclized derivatives of nemorosone. The instability of PPBs carrying an enolizable 1,3-diketone system has been suggested, and the elucidation of this aspect is very fundamental for the evaluation of their biologic activity. Electrospray ionization multistage tandem mass spectrometry (ESI-MS(n)) was employed to shed light on the origin of these derivatives of nemorosone and to define the stability of this natural product. For this purpose, we initially performed MS(n) experiments on seven related PPBs to obtain useful information for structural characterization of this class of compounds and to identify the degradation products of nemorosone. The proposed fragmentation pathways, supported by exact mass measurements, allowed the nature of side chains on the bicyclo core and the type and position of their modifications to be established. In a second part, the degradation profile of nemorosone under different conditions was investigated to assess the possible effects of isolation procedures, climatic, and storage conditions on its stability. Our results reveal that nemorosone undergoes rapid degradation in n-hexane and chloroform solutions. The degradation products, identified by HPLC-ESI/MS(n) and NMR, are identical to derivatives of nemorosone previously isolated from propolis and plants. Thus, these PPBs are artefacts formed predominantly during the extraction and purification procedures.

Bioassay-guided isolation of xanthones and polycyclic prenylated acylphloroglucinols from Garcinia oblongifolia

Bioassay-guided fractionation of the acetone extract of the bark of Garcinia oblongifolia has resulted in the isolation of three new xanthones, oblongixanthones A-C (1-3), three new polyprenylated benzoylphloroglucinols, oblongifolins E-G (4-6), and 12 known compounds. Oblongifolins I (5) and J (6) are the first natural products that have similar structural features to those of two known oxidation products of garcinol. The structures of the new compounds 1-6 were characterized by spectroscopic data interpretation. All isolates were assayed for their apoptosis-inducing effects against HeLa-C3 cells. Oblongifolin C (16) was found to be the most potent apoptotic inducer of the compounds evaluated.

Oblongifolins A-D, polyprenylated benzoylphloroglucinol derivatives from Garcinia oblongifolia

Oblongifolins A-D (2-5), four new polyprenylated 3,4-dihydroxybenzoylphloroglucinol compounds, were isolated from the bark of Garcinia oblongifolia collected in Vietnam. The bark was also found to contain the known compounds camboginol and guttiferone B. Extraction of the leaves gave 2 and camboginol. Details of the structure elucidation of 2-5 and stereochemical comparisons with known natural derivatives of general formula 1a,b are presented. The biological activity of these compounds concerning interactions with tubulin was investigated.