Differentiating Dyes: A Spectroscopic Investigation into the Composition of Scarlet Bloodroot (Haemodorum coccineum R.Br.) Rhizome

Haemodorum coccineum, commonly known as scarlet bloodroot, is a plant native to New Guinea and the northern most parts of Australia. The highly coloured H. coccineum is used by communities in Larrakia country for dyeing garments and occasionally to treat snake bites. Previous studies into H. coccineum have focused on its taxonomic classification, with this being the first evaluation of the chemical composition of the plant. Haemodoraceae plants are reported to contain phenylphenalenones (PhPs), which are highly conjugated polycyclic oxygenated aromatic hydrocarbons. We report the characterisation of 20 compounds extracted from the rhizome of H. coccineum: four sugars and 16 compounds belonging to the PhP family. The compounds include five aglycones and seven glycosylated compounds, of which four contain malonate esters in their structures. Characterisation of these compounds was achieved through 1D and 2D NMR, MS analysis and comparison to the known phytochemistry of other species from the Haemodorum genus. Preliminary anti-microbial activity of the crude extract shows significant inhibition of the growth of both gram-positive and gram-negative bacteria, but no activity against Candida albicans.

Diarylheptanoid Derivatives (Musellins A-F) and Dimeric Phenylphenalenones from Seed Coats of Musella lasiocarpa, the Chinese Dwarf Banana

Phenylphenalenones (PPs) are phytoalexins protecting banana plants (Musaceae) against various pathogens. However, how plants synthesize PPs is still poorly understood. In this work, we investigated the major secondary metabolites of developing seed coats of Musella lasiocarpa to determine if this species might be a good model system to study the biosynthesis of PPs. We found that PPs are major components of M. lasiocarpa seed coats at middle and late developmental stages. Two previously undescribed PP dimers (M-4 and M-6) and a group of unreported diarylheptanoid (DH) derivatives named musellins A-F (B-7, B-9, B-10, B-12, B-14, and B-15) were isolated along with 14 known compounds. Musellin D (B-12) and musellin F (B-15) contain the first reported furo[3,2-c]pyran ring and represent a previously undescribed carbon skeleton. The chemical structures of all new compounds were characterized by spectroscopic data, including NMR, HRESIMS, and ECD analysis. Plausible biosynthetic pathways for the formation of PPs and DHs are proposed.

Pharmacognostic Study, Diuretic Activity and Acute Oral Toxicity of the Leaves of Xiphidium caeruleum Aubl. Collected in Two Different Phenological Stages

Xiphidium caeruleum Aubl. is traditionally used in Cuba as an analgesic, anti-inflammatory, antilithiatic and diuretic remedy. Here we studied the pharmacognostic parameters of the leaves of X. caeruleum, the preliminary phytochemical composition, diuretic activity and acute oral toxicity of the aqueous extracts from the leaves of plants collected in the vegetative (VE) and flowering (FE) stages. The morphological characteristics and physicochemical parameters of leaves and extracts were determined. The phytochemical composition was assessed by phytochemical screening, TLC, UV, IR and HPLC/DAD profiles. The diuretic activity was evaluated in Wistar rats and compared to furosemide, hydrochlorothiazide and spironolactone. Epidermal cells, stomata and crystals were observed on the leaf surface. Phenolic compounds were identified as the main metabolites, including phenolic acids (gallic, caffeic, ferulic and cinnamic acids) and flavonoids (catechin, kaempferol-3-O-glucoside and quercetin). VE and FE showed diuretic activity. The activity of VE was similar to furosemide, and the activity of FE resembled spironolactone. No acute oral toxicity was observed. The presence of flavonoids and phenols in VE and FE may explain at least in part the traditional use and provide some insight into the reported ethnomedical use as a diuretic. Because of the differences in polyphenol profiles between VE and FE, further studies should be carried out to standardize the harvesting and extraction conditions in order to use X. caeruleum leaf extract as herbal medicine.

Phytochemical Profiling and Biological Testing of the Constituents of the Australian Plant Haemodorum brevisepalum

Phytochemical profiling was undertaken on the crude extracts of the bulbs, stems, and the fruits of Haemodorum brevisepalum, to determine the nature of the chemical constituents present. This represents the first study to investigate the fruits of a species of Haemodorum. In total, 13 new and 17 previously reported compounds were isolated and identified. The new compounds were of the phenylphenalenone-type class, with a representative of a novel structural form, named tentatively "oxabenzochromenone" (1), a compound akin to an intermediate in a recently proposed phenylphenalenone metabolic network (2), seven new phenylphenalenones (4-10), four new phenylbenzoisochromenones (11-14), and a new phenylbenzoisochromenone derivative (18). The previously reported compounds identified were of the following structure classes: oxabenzochrysenone (3, 23-26), flavonol (15, 16), phenylbenzoisochromenone (17, 21, 22, 27-30), and phenylphenalenone (19, 20). Compounds 2-4, 6-9, 15-18, 21, 22, and 26 were subjected to antimicrobial evaluation with moderate activity observed against Staphylococcus aureus MRSA and slight activity against Pseudomonas aeruginosa and Candida albicans. Compounds 4, 6-9, 17, and 21 were also evaluated for anthelminthic activity against larvae of the blood-feeding parasitic nematode Haemonchus contortus.

Talaromyoxaones A and B: Unusual Oxaphenalenone Spirolactones as Phosphatase Inhibitors from the Marine-Derived Fungus Talaromyces purpureogenus SCSIO 41517

(+)- and (-)-talaromyoxaones A and B (1 and 2, respectively), two new oxaphenalenone derivatives with a hemiacetal frame and an unprecedented spirolactone frame of a 2'H,3H,4'H-spiro[isobenzofuran-1,3'-pyran]-3-one unit that show biosynthetic enantiodivergence, and two new oxaphenalenone analogues (±)-11-apopyrenulin (3) and (+)- or (-)-abeopyrenulin (4) were isolated from the marine-derived fungus Talaromyces purpureogenus SCSIO 41517. Their structures were elucidated by spectroscopic analysis, single-crystal X-ray diffraction, and quantum chemical calculations of ECD spectra. Compounds 1 and 2 showed selective inhibitory activity against phosphatases SHP1, SHP2, and MEG2 with IC₅₀ values of 1.3-3.4 μM, and the potential modes of action for 1 were investigated by a preliminary molecular docking study.

Phytochemicals and Allelopathy of Induced Water Hyacinth against Microcystis aeruginosa

Induced water hyacinth with purple roots (PRWH) exerts a significant inhibitory effect on the growth of blue-green algae. Interestingly, its chemical constituents differ from those of wild-type water hyacinth and have not yet been reported. This study aimed to explore the chemical constituents of PRWH and its bioactive components serving as allelopathic agents against blue-green algae. Phytochemical investigation of the bioactive ethyl acetate fraction of a crude methanol extract from PRWH led to the isolation of 56 compounds, including 11 new phenylphenalene derivatives. The structures of these compounds were elucidated by comprehensive analyses through NMR, HRMS, and X-ray techniques. Bioactivity evaluation against Microcystis aeruginosa indicated that compounds 7, 12, 15, 37, 39, 45, and 47 potently inhibited blue-green algae growth.

Amino acid-derived defense metabolites from plants: A potential source to facilitate novel antimicrobial development

For millennia, humanity has relied on plants for its medicines, and modern pharmacology continues to reexamine and mine plant metabolites for novel compounds and to guide improvements in biological activity, bioavailability, and chemical stability. The critical problem of antibiotic resistance and increasing exposure to viral and parasitic diseases has spurred renewed interest into drug treatments for infectious diseases. In this context, an urgent revival of natural product discovery is globally underway with special attention directed toward the numerous and chemically diverse plant defensive compounds such as phytoalexins and phytoanticipins that combat herbivores, microbial pathogens, or competing plants. Moreover, advancements in “omics,” chemistry, and heterologous expression systems have facilitated the purification and characterization of plant metabolites and the identification of possible therapeutic targets. In this review, we describe several important amino acid–derived classes of plant defensive compounds, including antimicrobial peptides (e.g., defensins, thionins, and knottins), alkaloids, nonproteogenic amino acids, and phenylpropanoids as potential drug leads, examining their mechanisms of action, therapeutic targets, and structure–function relationships. Given their potent antibacterial, antifungal, antiparasitic, and antiviral properties, which can be superior to existing drugs, phytoalexins and phytoanticipins are an excellent resource to facilitate the rational design and development of antimicrobial drugs.

Genome-scale analyses of polyketide synthases in banana: Phylogenetics and expression profiling forecast their candidacy in specialized metabolism

Plant type III polyketide synthases (PKSs) are associated with various functions in plant growth, development and defense by providing a multitude of polyketide scaffolds for diverse specialized metabolic pathways (SMPs). To decipher banana PKSs involved in specialized metabolism, genome-wide comparative analyses were conducted with A (Musa acuminata) and B (Musa balbisiana) genomes of banana. Both genomes retained eight chalcone synthases (CHSs), seven curcumin synthases (CURSs), three diketidyl-CoA synthases (DCSs) and one anther specific CHS (ASC). Segmental (42%) and tandem (37%) duplication events majorly flourished the banana PKS family. Six of 19 PKSs of A genome (designated as MaPKSs) showed relatively a higher expression in the root, corm, sheath, leaf and embryogenic cell suspension (ECS) of banana. To determine the defense response of MaPKSs and to highlight their candidacy in various SMPs, expression profiling was conducted by qPCR in ECSs treated with 100/200 μM of jasmonic acid (JA) and salicylic acid (SA) at 24/48 h. Maximum and subordinate expression induction of MaPKSs was apparent respectively against JA and SA treatments. Notably, most MaPKSs achieved their peak expression within 24 h of JA and the total flavonoid content was reached maximum within 24 h of JA/SA elicitations. Considering the homology, phylogeny, and expression levels in each analyzed sample (n = 13), three CHSs, three DCSs along with three CURSs and one ASC were selected as most promising candidates respectively for flavonoids, phenylphenalenones and sporopollenin biosynthesis in banana. Our findings provide a first-line resource to disclose the functions of banana PKSs involved in distinct SMPs.

Allylsilane Reagent-Controlled Divergent Asymmetric Catalytic Reactions of 2-Naphthoquinone-1-methide

Herein, the first allylsilane reagent-controlled divergent asymmetric Hosomi-Sakurai conjugate allylation and hetero-Diels-Alder (HDA) with 2-naphthoquinone-1-methide (2-Nap-Q-1-M) under the catalysis of Sc^III /Feng ligand complex is reported. With these methods, a variety of uniquely substituted chiral allyl-functionalized diaryl compounds and naphthopyran products were obtained in a straightforward and highly stereoselective (up to 96.5:3.5 e.r.) manner under mild conditions. Moreover, it is demonstrated that 2-Nap-Q-1-M can serve as an efficient diene for a side asymmetric Diels-Alder (D-A) reaction. This principle can provide a straightforward access to hydrophenalene in an optically active form, which represents a structural core of various natural products and bioactive molecules.

Antimicrobial Evaluation of the Constituents Isolated From Macropidia fuliginosa (Hook.) Druce

Six compounds previously isolated and reported from Macropidia fuliginosa were evaluated for antimicrobial activity against 11 different microbial strains, with all compounds displaying broad spectrum activity. In addition, the compounds were also assessed for their antiproliferative activity and cytotoxicity. Further investigation of M. fuliginosa has led to the discovery of a previously described acenaphthylenediol from the bulbs of the plant.

The photoactivity of natural products - An overlooked potential of phytomedicines?

BACKGROUND

Photoactivity, though known for centuries, is only recently shifting back into focus as a treatment option against cancer and microbial infections. The external factor light is the ingenious key-component of this therapy: Since light activates the drug locally, a high level of selectivity is reached and side effects are avoided. The first reported photoactive medicines were plant extracts. Synthetic entities (so-called photosensitizers PSs), however, paved the route towards the clinical approval of the so-called photodynamic therapy (PDT), and thus natural PSs took a backseat in the past.

HYPOTHESIS

Many isolated bioactive phytochemicals hold a hidden photoactive potential, which is overlooked due to the reduced common awareness of photoactivity.

METHODS

A systematic review of reported natural PSs and their supposed medicinal application was conducted by employing PubMed, Scifinder, and Web of Science. The identified photoactive natural products were compiled including information about their natural sources, their photoyield, and their pharmacological application. Furthermore, the common chemical scaffolds of natural PS are shown to enable the reader to recognize potentially overlooked natural PSs.

RESULTS

The literature review revealed over 100 natural PS, excluding porphyrins. The PSs were classified according to their scaffold. Thereby it was shown that some PS-scaffolds were analyzed in a detailed way, while other classes were only scarcely investigated, which leaves space for future discoveries. In addition, the literature revealed that many PSs are phytoalexins, thus the selection of the starting material significantly matters in order to find new PSs.

CONCLUSION

Photoactive principles are ubiquitous and can be found in various plant extracts. With the increasing availability of light-irradiation setups for the identification of photoactive natural products, we anticipate the discovery of many new natural PSs in the near future. With the accumulation of chemically diverse PSs, PDT itself might finally reach its clinical breakthrough as a promising alternative treatment against multi-resistant microbes and cancer types.