Withanolide artifacts formed in methanol

Genus Physalis L.: A review of resources and cultivation, chemical composition, pharmacological effects and applications

ETHNOPHARMACOLOGICAL RELEVANCE

The genus Physalis L. (Solanaceae) is commonly used in the treatment of dermatitis, leprosy, bronchitis, pneumonia, hepatitis and rheumatism in China and other Asian countries.

AIM OF THE REVIEW

This article reviews the resources, cultivation, phytochemistry, pharmacological properties, and applications of Physalis L., and proposes further research strategies to enhance its therapeutic potential in treating various human diseases.

MATERIALS AND METHODS

We conducted a systematic search of electronic databases, including CNKI, SciFinder and PubMed, using the term "Physalis L." to collect information on the resources, phytochemistry, pharmacological activities, and applications of Physalis L. in China during the past ten years (2013.1-2023.1).

RESULTS

So far, a variety of chemical constituents have been isolated and identified from Physalis L. mainly including steroids, flavonoids, and so on. Various pharmacological activities were evaluated by studying different extracts of Physalis L., these activities include anti-inflammatory, antibacterial, antioxidant, antiviral, antineoplastic, and other aspects.

CONCLUSION

Physalis L. occupies an important position in the traditional medical system. It is cost-effective and is a significant plant with therapeutic applications in modern medicine. However, further in-depth studies are needed to determine the medical use of this plant resources and cultivation, chemical composition, pharmacological effects and applications.

The intramolecular SN2 reaction tautomeric ent-Kauranoids isolated from the aerial parts of Isodon amethystoides

As our ongoing searching for the bioactive natural terpenoids, nine ent-kauranoids (1-9), including three previously undescribed ones (1, 2, and 9), were isolated from the aerial parts of Isodon amethystoides. Their structures were elucidated on the basis of spectroscopic data analysis, including NMR, MS, and ECD. Compounds 1 and 2 were a pair of tautomeric compounds, which was confirmed by the HPLC analysis and low temperature NMR testing. The underlying mechanism of the tautomer was proposed as an intramolecular SN2 reaction, which was explained by quantum chemical calculation. The HOMO-LUMO gap and the free energy revealed the spontaneous of the tautomeric of the 1 and 2. Additionally, the similar phenomena were also found in the two groups of known compounds 3 and 4 and 6 and 7, respectively. Apart from the tautomer, compounds 3 and 4 can be hydrolyzed into 5 through ester hydrolysis in CDCl3, while compounds 6, 7 can be hydrolyzed into 8 through ester hydrolysis. These phenomena were also confirmed through HPLC analysis and low temperature nuclear magnetic resonance tests and the mechanism was studied using quantum chemical calculation.

Formation of Trideuteromethylated Artifacts of Pyrrole-Containing Natural Products

Pyrrole-containing natural products form a large group of structurally diverse compounds that occur in both terrestrial and marine organisms. In the present study the formation of trideuteromethylated artifacts of pyrrole-containing natural products was investigated, focusing on the discorhabdins. Three deuterated discorhabdins, 1, 3, and 5, were identified to be isolation procedure artifacts caused by the presence of DMSO-d6 during NMR sample preparation and handling. Three additional semisynthetic derivatives, 7-9, were made during the investigation of the mechanism of formation, which was shown to be driven by trideuteromethyl radicals in the presence of water, methanol, TFA, and traces of iron in the deuterated solvent. Generation of trideuteromethylated artifacts was also confirmed for other classes of pyrrole-containing metabolites, namely, makaluvamines, tambjamines, and dibromotryptamines, which had also been dissolved in DMSO-d6 during the structure elucidation process. Semisynthetic discorhabdins were assessed for antiproliferative activity against a panel of human tumor cell lines, and 14-trideuteromethyldiscorhabdin L (3) averaged low micromolar potency.

Anti-Inflammatory Peroxidized Chlorahololide-Type Dimers Are Artifacts of Shizukaol-Type Dimers: From Phenomena Discovery and Confirmation to Potential Underlying Mechanism

In our research on naturally occurring sesquiterpenes, eight shizukaol-type dimers, one chlorahololide-type dimer, and one sarcanolide-type dimer were isolated from the roots of Chloranthus fortunei. As the project was implemented, we accidentally discovered that shizukaol-type dimers can be converted into peroxidized chlorahololide-type dimers. This potential change was discovered after simulations of the changes in corresponding shizukaols showed that three peroxide products were generated (1-3), indicating that peroxidation reactions occurred. HPLC-HR-MS analysis results obtained for the shizukaol derivatives further demonstrate that the reaction occurred, and the type of substituent of small organic ester moieties at positions C-15' and C-13' of unit B were not decisively related to the reaction. Quantum chemical calculations of the mode dimer further demonstrated this phenomenon. The highest occupied molecular orbital (HOMO)-lowest unoccupied molecular orbital (LUMO) energy of the precursor and production revealed the advantageous yield of 4β-hydroperoxyl production. Additionally, the potential reaction mechanism was speculated and validated using the free energy in the reaction which successfully explained the feasibility of the reaction. Finally, the anti-inflammatory activity of the precursors and products was evaluated, and the products of peroxidation showed better anti-inflammatory activity.

Natural withanolides, an update

Covering: March 2010 to December 2020. Previous review: Nat. Prod. Rep., 2011, 28, 705This review summarizes the latest progress and perspectives on the structural classification, biological activities and mechanisms, metabolism and pharmacokinetic investigations, biosynthesis, chemical synthesis and structural modifications, as well as future research directions of the promising natural withanolides. The literature from March 2010 to December 2020 is reviewed, and 287 references are cited.

Silica Gel-mediated Oxidation of Prenyl Motifs Generates Natural Product-Like Artifacts

Prenyl moieties are commonly encountered in the natural products of terpenoid and mixed biosynthetic origin. The reactivity of unsaturated prenyl motifs is less recognized and shown here to affect the acyclic Rhodiola rosea monoterpene glycoside, kenposide A (8: ), which oxidizes readily on silica gel when exposed to air. The major degradation product mediated under these conditions was a new aldehyde, 9: . Exhibiting a shortened carbon skeleton formed through the breakdown of the terminal isopropenyl group, 9: is prone to acetalization in protic solvents. Further investigation of minor degradation products of both 8: and 8-prenylapigenin (8-PA, 12: ), a flavonoid with an ortho-prenyl substituent, revealed that the aldehyde formation was likely realized through epoxidation and subsequent cleavage at the prenyl olefinic bond. Employment of ¹H NMR full spin analysis (HiFSA) achieved the assignment of all chemical shifts and coupling constants of the investigated terpenoids and facilitated the structural validation of the degradation product, 9: . This study indicates that prenylated compounds are generally susceptible to oxidative degradation, particularly in the presence of catalytic mediators, but also under physiological conditions. Such oxidative artifact/metabolite formation leads to a series of compounds with prenyl-derived (cyclic) partial structures that are analogous to species formed during Phase I metabolism in vivo. Phytochemical and pharmacological studies should take precautions or at least consider the impact of (unavoidable) exposure of prenyl-containing compounds to catalytic and/or oxidative conditions.

Withanolides from dietary tomatillo suppress HT1080 cancer cell growth by targeting mutant IDH1

Isocitrate dehydrogenase (IDH) is one key rate-limiting enzyme in the tricarboxylic acid cycle, which is related to various cancers. Tomatillo (Physalis ixocarpa), a special tomato, is widely consumed as nutritious vegetable in Mexico, USA, etc. As a rich source for withanolides, the fruits of P. ixocarpa were investigated, leading to the isolation of 11 type-A withanolides including 4 new ones (1 is an artificial withanolide). All these withanolides were evaluated for their inhibition on mutant IDH1 enzyme activity. Among them, physalin F (11) exhibited potent enzyme inhibitory activity and binding affinity with mutant IDH1. It inhibits the proliferation of HT1080 cells by selectively inhibiting the activity of mutant IDH1. Since Ixocarpalactone A, another major type-B withanolide in this plant, could act on another energy metabolism target PHGDH, the presence of different types of withanolides in tomatillo and their synergistic effect could make it a potential antitumor functional food or drug.

Withanolides isolated from Tubocapsicum anomalum and their antiproliferative activity

Seven undescribed withanolides (1-7) and six artificial withanolides (8-13), along with 20 known compounds (14-33) were isolated from the aerial parts of Tubocapsicum anomalum. Their structures were confirmed by comprehensive spectroscopic analyses. The absolute configuration of compound 1 was defined by single-crystal X-ray crystallography. All isolates were evaluated for their antiproliferative effects against five human tumor cell lines (Hep3B, MDA-MB-231, SW480, HCT116 and A549), among which compound 24 (tubocapsanolide A) exhibited the highest activities against the MDA-MB-231 cells with an IC₅₀ value of 1.89 ± 1.03 μM. Further studies showed that 24 exhibited significant damage to mitochondria in MDA-MB-231 cells, including excess reactive oxygen species, decreased mitochondrial membrane potential, and apoptosis initiation. In addition, compound 24 also inhibited cell migration. These findings show that tubocapsanolide A may be a promising molecule for triple-negative breast cancer treatment and merit further evaluation.

New cytotoxic withanolides from Physalis minima

Phytochemical investigation of Physalis minima led to the isolation of six new withanolides, including physaminilides HK (1-4), two artificial withanolides (5-6), and 19 known ones (7-25). Their structures were elucidated on the basis of spectroscopic analysis, including NMR and electronic circular dichroism (ECD) data. The isolates were evaluated for their cytotoxic activities against A375 human melanoma cells. Compounds 1, 8-9, 12-13, 15-17 and 19 exhibited significant cytotoxic activities with IC₅₀ values in the range of 1.2-7.5 μM.

New withanolides from Physalis minima and their cytotoxicity against A375 human melanoma cells

The new withanolides physaminilide A–G (1–7), and two artificial withanolides (8–9) were isolated from Physalis minima. Compounds 2, 5 and 8 exhibited significant cytotoxicity towards human tumor cells.

Labdanes, Withanolides, and Other Constituents from Physalis nicandroides

Chemical investigation of the aerial parts (except fruits and calixes) of Physalis nicandroides var. attenuata led to the isolation of a series of new labdane-type diterpenoids, including the closely related compounds 1-3, the labdane glucosides 4 and 5, a mixture of the epimeric alcohols 6 and 7, and one labdanetriol, isolated as its tri-O-acetyl derivative 9. In addition, three new withanolides (14-16) and six known compounds were isolated. The structures of these compounds were elucidated by analysis of their spectroscopic data and chemical transformations, and those of compounds 1, 4, and 16 were confirmed by X-ray diffraction analysis of the natural product (1) and of the corresponding acetyl derivatives 4a and 16a. Fourteen of these compounds were assayed for their in vitro inhibitory activity against yeast α-glucosidase and acetylcholinesterase enzymes. The results were negative in both cases, except for compound 3a that marginally inhibited the activity of acetylcholinesterase with an IC₅₀ value of 64.4 μM.

Prealamethicin F50 and related peptaibols from Trichoderma arundinaceum: Validation of their authenticity via in situ chemical analysis

In the field of natural products chemistry, a common question pertains to the authenticity of an isolated compound, i.e. are the interesting side chains biosynthesized naturally or an artefact of the isolation/purification processes? The droplet-liquid microjunction-surface sampling probe (droplet-LMJ-SSP) coupled to a hyphenated system (UPLC-UV-HRESIMS) empowers the analysis of natural product sources in situ, providing data on the biosynthetic timing and spatial distribution of secondary metabolites. In this study the droplet-LMJ-SSP was utilized to validate the authenticity of two new peptaibols (2 and 3) as biosynthesized secondary metabolites, even though both them had structural features that could be perceived as artefacts. Compounds 2 and 3 were isolated from the scaled up fermentation of Trichoderma arundinaceum (strain MSX70741), along with a new member of the trichobrevin BIII complex (1), and four known compounds (4-7). The structures of the isolates were established using a set of spectroscopic and spectrometric methods, and their absolute configurations were determined by Marfey's analysis. The cytotoxic activity of compounds 1, 3, 4 and 6 was evaluated against a panel of cancer cell lines, where cytotoxic activity in the single digit μM range was observed.

Stereo- and region-specific biotransformation of physapubescin by four fungal strains

Biotransformations of physapubescin (1) were performed by four fungal strains-Mucor subtilissimus AS 3.2454, Mucor polymorphosporus AS 3.3443, Aspergillus niger AS 3.795, and Syncephalastrum racemosum AS 3.264. Four metabolites were prepared in the biotransformation process of 1, and their structures were elucidated as 15α-acetoxy-5,6β:22,26:24,25-triepoxy-26α-hydroxy-3β-methoxy 4β-hydroxyergost-1-one (2), 15α-acetoxy-5,6β:22,26-diepoxy-4β,24β,25α,26(α, β)-tetrahydroxyergost-3β-methoxy-1-one (3a/3b), 15α-acetoxy-5,6β:22,26-diepoxy-4β,24β,25α,26(α, β)-tetrahydroxyergost-2-en-1-one (4a/4b), and physapubescin D (5), by spectroscopic data analysis. Among them, metabolites 2 and 3 are new. All of these fungal strains showed the ability to be highly stereo- and region-specific for the bioconversion of substrate (1). Our research provides a reference for the structural derivatization of withanolides or possibly even other natural products.

Withanolides from leaves of cultivated Acnistus arborescens

Seven withanolides, including four previously unknown, were isolated from the acetone and ethanol extracts of cultivated specimens of Acnistus arborescens. These four compounds were identified as rel-(18R,22R)-5β,6β:18β,20-diepoxy-3β,18α-dimethoxy-4β-hydroxy-1-oxowith-24-enolide, rel-(20R,22R)-5β,6β-epoxy-4β,16α,20-trihydroxy-1-oxowitha-2,24dienolide, rel-(20R,22R)-16α-acetoxy-6α-chloro-4β,5β,20-trihydroxy-1-oxowitha-2,24-dienolide and rel-(20R,22R)-16α-acetoxy-20-hydroxy-1-oxowitha-2,5,24-trienolide. Their structures were elucidated by interpretation of spectroscopic data (1D and 2D NMR), HRESIMS experiments and comparison with published data for similar compounds. Cytotoxicity of the isolated compounds was evaluated against a panel of four tumor cell lines (HL-60, HCT-116, SF-268 and PANC-1). Withanolide D was the most active, with an IC50 value in the range of 0.3-1.7 μM, rel-(18R,22R)-5β,6β:18β,20-diepoxy-3β,18α-dimethoxy-4β-hydroxy-1-oxowith-24-enolide and rel-(20R,22R)-5β,6β-epoxy-4β,16α,20-trihydroxy-1-oxowitha-2,24dienolide were moderately active, while all the others were non-cytotoxic.

Sesquiterpenoids Isolated from Two Species of the Asteriscus Alliance

Investigation of the aerial parts of two Spanish members of the Asteriscus alliance, Asteriscus graveolens subsp. stenophyllus and Asteriscus schultzii, afforded four new sesquiterpene lactones containing a humulene skeleton (1-4) and one new sesquiterpene lactone of the asteriscanolide type (5). Their chemical structures were determined on the basis of the HRMS and from 1D and 2D NMR spectroscopic studies. Both species showed different profiles of sesquiterpenoid constituents. A. schultzii did not show humulene or asteriscane sesquiterpenes, suggesting a resemblance to the genus Pallenis, another member of the Asteriscus alliance. A literature review on chemical isolates from the Asteriscus alliance supported the placement of A. schultzii in the genus Pallenis. The isolated components (1-5) were assessed for cytotoxicity against the HL-60 and MOLT-3 leukemia cell lines, with compound 1 showing activity in both biological assays (IC50 value range 4.1-5.4 μM).

Analysis of Major Withanolides in Physalis longifolia Nutt. by HPLC-PDA

An analytical method based on high-performance liquid chromatography-photodiode array detection was developed for the simultaneous determination of three anti-proliferative withanolides [withalongolide A ( 1: ), withaferin A ( 2: ) and withalongolide B ( 3: )] present in the aboveground biomass of the long-leaf groundcherry, Physalis longifolia. This method was achieved by biomass extraction followed by chromatographic separation on C18 column eluted with a gradient acetonitrile-water mobile phase. Calibration curves produced satisfactory linear regression (r(2) > 0.9995) for each examined sample. The method was also validated for accuracy, precision and limits of detection and quantification. Such an approach is applicable for the rapid detection and quantitative assessment of withanolides in various P. longifolia accessions.

Antiproliferative withanolides from several solanaceous species

To date, our work on solanaceous species (Datura wrightii, Jaborosa caulescens, Physalis hispida, Physalis longifolia, Vassobia breviflora and Withania somnifera) has resulted in the isolation of 65 withanolides, 31 of which were new, as well as the semi-synthesis of a further 30 withanolides. Structure identification and MTS assay-based antiproliferative evaluation of these 95 compounds revealed that a Δ(2)-1-oxo functionality in ring A, in conjunction with either a 5β,6β-epoxy or 5α-chloro-6β-hydroxy moiety in ring B, is the minimum structural requirement for withanolides to produce potent cytotoxic activity. Such structure-activity relationship analysis also revealed that oxygenation (the -OH or -OR groups) at C-4, 7, 11 and 12, as well as C-14 to C-28, did not contribute towards the observed antiproliferative activity. Herein, we present a complete overview of our work as it relates to the withanolides reported from 1965 to 2013.