A new phenolic constituent and a cyanogenic glycoside from Balanophora involucrata (Balanophoraceae)

The genus Balanophora J. R. Forst. & G. Forst. - Its use in traditional medicine, phytochemistry, and pharmacology: A review

ETHNOPHARMACOLOGICAL RELEVANCE

Natural products, particularly medicinal plants, have been utilized in traditional medicine for millennia to treat various diseases. The genus Balanophora (Balanophoraceae) consists of 23 accepted species. These species are the most controversial flowering plants, with highly reduced morphologies and are found parasitizing on the roots of their host. They have been used in traditional medicine as a remedy for stomach pain, detumescence, uterine prolapse, wounds, syphilis, gonorrhea, treating injuries from falls, and other conditions. However, there is no review of this genus on its traditional uses, phytochemistry, and pharmacology.

AIM

The present narrative review discusses the scientific data supporting the traditional uses of Balanophora species. The available information on its botanical properties, traditional uses, chemical contents, pharmacological activities, and toxicity was summarized to help comprehend current research and offer a foundation for future research.

MATERIALS AND METHODS

The materials used in combining data on the genus Balanophora comprises online sources such as Web of Science, Google Scholar, Science Direct, and Chinese National Knowledge Infrastructure (CNKI) for Chinese-related materials. World Flora online was used in validating the scientific names of this genus while ChemBio Draw Ultra Version 22.2 software was employed in drawing the phytochemical compounds.

RESULTS

Nine Balanophora species including B. harlandii, B. japonica, B. polyandra, B. fungosa, B. fungosa subsp. indica, B. laxiflora, B. abbreviata, B. tobiracola, and B. involucrata have been documented as vital sources of traditional medicines in different parts of Asia. A total of 159 secondary metabolites have been isolated and identified from the ten species of this genus comprising tannins, flavonoids, sterols, lignans, chalcones, terpenes, and phenylpropanoids. Among these compounds, tannins, lignans, terpenoids, chalcones and phenolic acids contribute to the pharmacological activities of the species in this genus with several biological activities both in vitro and in vivo such as anti-inflammatory, anti-oxidant, hypoglycemic activity, cytotoxicity, anti-microbial, melanin synthesis etc. CONCLUSION: This review summarizes the available literature on the traditional uses, pharmacological properties, and phytoconstituents of Balanophora species indicating that they contain fascinating chemical compounds with diverse biological activities. The traditional uses of the species in this genus have been confirmed by scientific data such as antimicrobial, hemostatic effect, gastroprotective activity and others. However, many species in this genus are yet unknown in terms of their botanical uses, chemical composition and biological activities. Thus, more research into the scientific connections between traditional medicinal uses and pharmacological activities, mode of action of the isolated bioactive constituents, and toxicity of other Balanophora species is needed to determine their efficacy and therapeutic potential for safe clinical application.

Natural Products Containing the Nitrile Functional Group and Their Biological Activities

The importance of nitriles as a key class of chemicals with applications across the sciences is widely appreciated. The natural world is an underappreciated source of chemically diverse nitriles. With this in mind, this review describes novel nitrile-containing molecules isolated from natural sources from 1998 to 2021, as well as a discussion of the biological activity of these compounds. This study gathers 192 molecules from varied origins across the plant, animal, and microbial worlds. Their biological activity is extremely diverse, with many potential medicinal applications.

An UHPLC/LC-MS illustrated the dynamic profiling of balanophorin B, gallic acid, and 4-hydroxycinnamic acid in rat as 3 molecular entities from Balanophora simaoensis

An UHPLC/LC-MS was founded to detect balanophorin B (B), gallic acid (GA), 4-hydroxycinnamic acid (HC), and their in vivo profiling in rats, after oral administration of the ethanol extract of Balanophora simaoensis S. Y. Chang et Tam. The in vivo dynamic existence of 3 molecular entities in rats and the multistep biotransformation of GA were elucidated by their sensitive mass spectrometry response after efficient UHPLC and/or HPLC separation, through analyzing the bio-samples of rat plasma, bile, liver, kidneys, and excreta. The method was validated with satisfactory calibration curves having correlation coefficients r from 0.996 to 0.999 for concentration scaled from 0.100 nM to 0.100 μM, internal standard normalized matrix factors ranged from 0.923 to 0.993, sextuplicate recoveries valued from 95.0% to 103.6%, as well as accuracy and precision varied from 95.6% to 103.7%. The content of B, GA, and HC in the whole herb was of 4.66, 63.5, and 10.4 μmol/kg in dry weight, respectively. The Cmax for B, GA, and HC in rat systemic circulation was of 76.0 nM, 2.30 μM, and 51.0 μM, with tmax at 3, 2, and 2 h, respectively. B and GA stayed in rat liver over 4 hs to present a material base for the pharmacology and pharmacodynamics of the whole herb. The biotransformation of GA indicated a complicated scheme in rats. As a final metabolite from GA with total biotransformation conversion over 20%, 4-hydroxybenzaldehyde resourced from two steps of dehydroxylation and one step of reduction of GA, but not concerned with HC.

Chemical Diversity of Plant Cyanogenic Glycosides: An Overview of Reported Natural Products

Cyanogenic glycosides are an important and widespread class of plant natural products, which are however structurally less diverse than many other classes of natural products. So far, 112 naturally occurring cyanogenic glycosides have been described in the phytochemical literature. Currently, these unique compounds have been reported from more than 2500 plant species. Natural cyanogenic glycosides show variations regarding both the aglycone and the sugar part of the molecules. The predominant sugar moiety is glucose but many substitution patterns of this glucose moiety exist in nature. Regarding the aglycone moiety, four different basic classes can be distinguished, aliphatic, cyclic, aromatic, and heterocyclic aglycones. Our overview covers all cyanogenic glycosides isolated from plants and includes 33 compounds with a non-cyclic aglycone, 20 cyclopentane derivatives, 55 natural products with an aromatic aglycone, and four dihydropyridone derivatives. In the following sections, we will provide an overview about the chemical diversity known so far and mention the first source from which the respective compounds had been isolated. This review will serve as a first reference for researchers trying to find new cyanogenic glycosides and highlights some gaps in the knowledge about the exact structures of already described compounds.

Phenolics from the Bolivian highlands food plant Ombrophytum subterraneum (Aspl.) B. Hansen (Balanophoraceae): Antioxidant and α-glucosidase inhibitory activity

The Balanophoraceae Ombrophytum subterraneum is an endemic highland food plant occurring in Bolivia, northern Argentina and Chile. The upper part of this parasitic plant is eaten fresh. The aim of this work was to characterize the compounds occurring in the edible part and to assess any differences between the inflorescence and tuber. Ethanol extracts of the different plant parts were analyzed for antioxidant activity by the ORAC, TEAC, FRAP, CUPRAC and DPPH methods as well as for the effect on enzymes related to metabolic syndrome (α-amylase, α-glucosidase and pancreatic lipase). The main constituents were isolated by a combination of gel permeation in Sephadex LH-20 and countercurrent chromatography (CCC). Five compounds were isolated and fully identified by spectroscopic and spectrometric means. The new 3',5,5',7-tetrahydroxyflavanone 7-O-β-D-1 → 6 diglucoside was isolated for the first time. HPLC-ESI-MS/MS analysis allowed the identification of 19 compounds, including flavanones, flavanols, flavonols, dehydroflavonols and lignans, mainly as glycosides. A strong inhibition towards α-glucosidase was observed for the edible parts (IC₅₀: 1.46 µg/mL) as well as for the tuber and inflorescence (IC₅₀: 1.56 µg/mL and 0.87 µg/mL, respectively). A significant correlation was established between the total phenolic and the antioxidant capacity of the extracts as well as with the content of the new flavanone diglucoside. This is the first comprehensive report on the naturally occurring antioxidants and enzyme inhibitors from this native highland food resource.

Anti-neuraminidase activity of chemical constituents of Balanophora involucrata

Balanophora involucrata J. D. Hooker has been known to possess potential anti-inflammatory and antibacterial activities; however, its antiviral activity has not been evaluated so far. In order to find new neuraminidase inhibitors (NAIs), the neuraminidase (NA) inhibition activity of different B. involucrata extracts was evaluated. In this study, an in vitro NA inhibition assay was performed to identify which extract of B. involucrata exhibits (maximal) inhibitory activity against NA. Ultra high performance liquid chromatography/quadrupole time-of-flight-tandem mass spectroscopy (MS/MS) and molecular docking techniques were used to identify the specific compounds responsible for the anti-influenza activity of the extract, and to explore the potential natural NAIs. The ethyl acetate extract of B. involucrata exhibited significant inhibitory activity against NA with 50% inhibitory concentration (IC₅₀ ) value of 159.5 μg/mL. Twenty compounds were identified according to the MS/MS spectra; among them two compounds (quercitrin and phloridzin) showed obvious inhibitory activity against NA, with IC₅₀ of 311.76 and 347.32 μmol/L, respectively. This study suggested that B. involucrata can be a potential natural source of NAIs and may be useful in the fight against ferocious influenza viruses.

Antibacterial pyrrolidinyl and piperidinyl substituted 2,4-diacetylphloroglucinols from Pseudomonas protegens UP46

In the search for new antibiotic compounds, fractionation of Pseudomonas protegens UP46 culture extracts afforded several known Pseudomonas compounds, including 2,4-diacetylphloroglucinol (DAPG), as well as two new antibacterial alkaloids, 6-(pyrrolidin-2-yl)DAPG (1) and 6-(piperidin-2-yl)DAPG (2). The structures of 1 and 2 were determined by nuclear magnetic resonance spectroscopy and mass spectrometry. Compounds 1 and 2 were found to have antibacterial activity against the Gram-positive bacteria Staphylococcus aureus and Bacillus cereus, with minimal inhibitory concentration (MIC) 2 and 4 μg ml^-1, respectively, for 1, and 2 μg ml^-1 for both pathogens for 2. The MICs for 1 and 2, against all tested Gram-negative bacteria, were >32 μg ml^-1. The half maximal inhibitory concentrations against HepG2 cells for compounds 1 and 2 were 11 and 18 μg ml^-1, respectively, which suggested 1 and 2 be too toxic for further evaluation as possible new antibacterial drugs. Stable isotope labelling experiments showed the pyrrolidinyl group of 1 to originate from ornithine and the piperidinyl group of 2 to originate from lysine. The P. protegens acetyl transferase (PpATase) is involved in the biosynthesis of monoacetylphloroglucinol and DAPG. No optical rotation was detected for 1 or 2, and a possible reason for this was investigated by studying if the PpATase may catalyse a stereo-non-specific introduction of the pyrrolidinyl/piperidinyl group in 1 and 2, but unless the PpATase can be subjected to major conformational changes, the enzyme cannot be involved in this reaction. The PpATase is, however, likely to catalyse the formation of 2,4,6-triacetylphloroglucinol from DAPG.

Compounds from the fruits of mangrove Sonneratia apetala: Isolation, molecular docking and antiaging effects using a Caenorhabditis elegans model

The chemical investigation of the fruits of a mangrove Sonneratia apetala collected from the Beibu Gulf led to the isolation of four new compounds, sonneradons A-D (1-4), as well as 18 known compounds (5-22). The structures of the new compounds were elucidated based on extensive spectroscopic analysis, and the structures of the known compounds were established by comparison of their spectroscopic data with those of related metabolites. The antiaging activities of all isolates were evaluated using the nematode Caenorhabditis elegans as a model organism. The results showed that 10 compounds could protect C. elegans by extending its lifespan. Compound 1 possessed the most potent effect in the anti-heat stress assay and significantly attenuated aging-related decreases in the pumping and bending of the nematodes in the healthspan assay. Molecular docking studies suggested that compound 1 was bound to the DNA binding domain of HSF-1 and promoted the conformation of HSF-1, thus strengthening the interaction between the HSF-1 and related DNA. GLN49, ASN-74, and LYS-80 of the binding region might be the key amino residues during the interaction.

Phytochemical profile of Paulownia tomentosa (Thunb). Steud

Paulownia tomentosa, a member of the plant family Paulowniaceae and a rich source of biologically active secondary metabolites, is traditionally used in Chinese herbal medicine. Flavonoids, lignans, phenolic glycosides, quinones, terpenoids, glycerides, phenolic acids, and miscellaneous other compounds have been isolated from different parts of P. tomentosa plant. Recent interest in this species has focused on isolating and identifying of prenylated flavonoids, that exhibit potent antioxidant, antibacterial, and antiphlogistic activities and inhibit severe acute respiratory syndrome coronavirus papain-like protease. They show cytotoxic activity against various human cancer cell lines and inhibit the effects of human cholinesterase, butyrylcholinesterase, and bacterial neuraminidases. Most of the compounds considered here have never been isolated from any other species of plant. This review summarizes the information about the isolated compounds that are active, their bioactivities, and the structure-activity relationships that have been worked out for them.