A yellow chlorophyll catabolite in leaves of Urtica dioica L.: An overlooked phytochemical that contributes to health benefits of stinging nettle

Urtica dioica: Anticancer Properties and Other Systemic Health Benefits from In Vitro to Clinical Trials

While conventional medicine has advanced in recent years, there are still concerns about its potential adverse reactions. The ethnopharmacological knowledge established over many centuries and the existence of a variety of metabolites have made medicinal plants, such as the stinging nettle plant, an invaluable resource for treating a wide range of health conditions, considering its minimal adverse effects on human health. The aim of this review is to highlight the therapeutic benefits and biological activities of the edible Urtica dioica (UD) plant with an emphasis on its selective chemo-preventive properties against various types of cancer, whereby we decipher the mechanism of action of UD on various cancers including prostate, breast, leukemia, and colon in addition to evaluating its antidiabetic, microbial, and inflammatory properties. We further highlight the systemic protective effects of UD on the liver, reproductive, excretory, cardiovascular, nervous, and digestive systems. We present a critical assessment of the results obtained from in vitro and in vivo studies as well as clinical trials to highlight the gaps that require further exploration for future prospective studies.

Novel Types of Phyllobilins in a Fern - Molecular Reporters of the Evolution of Chlorophyll Breakdown in the Paleozoic Era

Breakdown of chlorophyll (Chl), as studied in angiosperms, follows the pheophorbide a oxygenase/phyllobilin (PaO/PB) pathway, furnishing linear tetrapyrroles, named phyllobilins (PBs). In an investigation with fern leaves we have discovered iso-phyllobilanones (iPBs) with an intriguingly rearranged and oxidized carbon skeleton. We report here a key second group of iPBs from the fern and on their structure analysis. Previously, these additional Chl-catabolites escaped their characterization, since they exist in aqueous media as mixtures of equilibrating isomers. However, their chemical dehydration furnished stable iPB-derivatives that allowed the delineation of the enigmatic structures and chemistry of the original natural catabolites. The structures of all fern-iPBs reflect the early core steps of a PaO/PB-type pathway and the PB-to-iPB carbon skeleton rearrangement. A striking further degradative chemical ring-cleavage was observed, proposed to consume singlet molecular oxygen (1O2). Hence, Chl-catabolites may play a novel active role in detoxifying cellular 1O2. The critical deviations from the PaO/PB pathway, found in the fern, reflect evolutionary developments of Chl-breakdown in the green plants in the Paleozoic era.

Structural Characterization, and Antioxidative and Anti-inflammatory Activities of Phylloxanthobilins in Tropaeolum majus, a Plant with Relevance in Phytomedicine

Tropaeolum majus (garden nasturtium) is a plant with relevance in phytomedicine, appreciated not only for its pharmaceutical activities, but also for its beautiful leaves and flowers. Here, we investigated the phytochemical composition of senescent nasturtium leaves. Indeed, we identified yellow chlorophyll catabolites, also termed phylloxanthobilins, which we show to contribute to the bright yellow color of the leaves in the autumn season. Moreover, we isolated and characterized the phylloxanthobilins from T. majus, and report the identification of a pyro-phylloxanthobilin, so far only accessible by chemical synthesis. We show that the phylloxanthobilins contribute to bioactivities of T. majus by displaying strong anti-oxidative effects in vitro and in cellulo, and anti-inflammatory effects as assessed by COX-1 and COX-2 enzyme inhibition, similar to other bioactive ingredients of T. majus, isoquercitrin, and chlorogenic acid. Hence, phylloxanthobilins could play a role in the efficacy of T. majus in the treatment of urinary tract infections, an established indication of T. majus. With the results shown in this study, we aid in the completion of the phytochemical profile of T. majus by identifying additional bioactive natural products as relevant components of this medicinal plant.

Anti-BPH lignans from Urtica triangularis subsp. pinnatifida (Hand.-Mazz.) C.J.Chen

A new lignan named (-)-ginkgool-9-O-β-glucopyranoside (1) together with eight known lignans (2-9) were isolated from Urtica triangularis subsp. pinnatifida (Hand.-Mazz.) C.J.Chen. According to the mass spectrometry and spectroscopic analyses, the gross structure and absolute configuration of the new lignan were elucidated. The cytotoxic effects of compounds 1-9 on BPH-1 cells and the docking results on type II 5α-reductase were analysed to evaluate their anti-BPH activity. The results showed better anti-BPH activity that compound 4 displaying an IC50 of 79.75 ± 3.68 μM than finasteride presenting an IC50 of 91.8 ± 3.74 μM. Compounds 1, 2 and 5 had moderate anti-BPH activity compared with finasteride.

Phyllobilins - Bioactive Natural Products Derived from Chlorophyll - Plant Origins, Structures, Absorption Spectra, and Biomedical Properties

Phyllobilins are open-chain products of the biological degradation of chlorophyll a in higher plants. Recent studies reveal that phyllobilins exert anti-oxidative and anti-inflammatory properties, as well as activities against cancer cells, that contribute to the human health benefits of numerous plants. In general, phyllobilins have been overlooked in phytochemical analyses, and - more importantly - in the analyses of medicinal plant extracts. Nevertheless, over the past three decades, > 70 phyllobilins have been identified upon examination of more than 30 plant species. Eight distinct chromophoric classes of phyllobilins are known: phyllolumibilins (PluBs), phylloleucobilins (PleBs), phylloxanthobilins (PxBs), and phylloroseobilins (PrBs)-each in type-I or type-II groups. Here, we present a database of absorption and fluorescence spectra that has been compiled of 73 phyllobilins to facilitate identification in phytochemical analyses. The spectra are provided in digital form and can be viewed and downloaded at www.photochemcad.com. The present review describes the plant origin, molecular structure, and absorption and fluorescence features of the 73 phyllobilins, along with an overview of key medicinal properties. The review should provide an enabling tool for the community for the straightforward identification of phyllobilins in plant extracts, and the foundation for deeper understanding of these ubiquitous but underexamined plant-derived micronutrients for human health.

The advent of phyllobilins as bioactive phytochemicals – natural compounds derived from chlorophyll in medicinal plants and food with immunomodulatory activities

The degradation of the green plant pigment chlorophyll has fascinated chemists and biologists alike over the last few decades. Bioactivities of the compounds formed in this biochemical degradation pathway, however, have only come to light recently. These natural compounds that are formed from chlorophyll during plant senescence are now called phyllobilins. In this review, we shortly discuss chlorophyll degradation and outline the so-far known bioactivities of selected phyllobilins (phylloleucobilin, dioxobilin-type phylloleucobilin, and phylloxanthobilin), and we also highlight the recently discovered immunomodulatory effects of a yellow phylloxanthobilin.

Comparative Metagenomics Reveals Microbial Communities and Their Associated Functions in Two Types of Fuzhuan Brick Tea

Fuzhuan brick tea (FBT) is a unique post-fermented tea product, naturally co-fermented by microorganisms, and has gained global popularity due to its potential health benefits for humans. Considerable efforts have been made toward elucidating the microbial diversity within FBT, but an understanding of the underlying FBT community interactions and functions remains poorly studied. Consequently, the microbial communities of two types of FBT, originating from Hunan and Shaanxi provinces, were investigated using comparative shotgun metagenomic sequencing and functional annotations. Metagenomic analysis indicated that two communities shared similar taxonomic and functional attributes. Two samples shared 486 genera, in which Pseudomonas contributed most to the abundant functions within the two samples. The carbohydrate active enzyme functions of the communities primarily comprised GH (32.92%), GT (26.8%), CEs (20.43%), and AAs (18.04%). Furthermore, the overall metabolic pathways encoded by the metagenomes were largely associated with carbohydrate and amino acid metabolism, with nine metabolic pathways that were differential between two groups including penicillin and cephalosporin biosynthesis. Significantly, a total of 35 potential probiotics were inferred, with Pseudomonas putida being the most abundant inferred probiotic (80%) within the FBT communities. This study provides new insights into FBT microbial communities on their potential functions and roles in FBT characteristics.

Tetrapyrrolic Pigments from Heme- and Chlorophyll Breakdown are Actin-Targeting Compounds

Chlorophyll and heme are among the "pigments of life", tetrapyrrolic structures, without which life on Earth would not be possible. Their catabolites, the phyllobilins and the bilins, respectively, share not only structural features, but also a similar story: Long considered waste products of detoxification processes, important bioactivities for both classes have now been demonstrated. For phyllobilins, however, research on physiological roles is sparse. Here, we introduce actin, the major component of the cytoskeleton, as the first discovered target of phyllobilins and as a novel target of bilins. We demonstrate the inhibition of actin dynamics in vitro and effects on actin and related processes in cancer cells. A direct interaction with G-actin is shown by in silico studies and confirmed by affinity chromatography. Our findings open a new chapter in bioactivities of tetrapyrroles-especially phyllobilins-for which they form the basis for broad implications in plant science, ecology, and physiology.

Phyllobilins as a challenging diverse natural product class: Exploration of pharmacological activities

Phyllobilins are a group of chlorophyll-derived bilin-type linear tetrapyrroles, generated in the process of chlorophyll breakdown. Since the first phyllobilin was isolated and characterized in 1991, more and more structures of these chlorophyll catabolites were identified alongside the biochemical players involved in chlorophyll breakdown. In the meantime, phyllobilins are known to occur in a large natural structural variety, and new modifications are still being discovered. Phyllobilins have been regarded as products of chlorophyll detoxification for a very long time, hence they have been completely overlooked as a natural product class in terms of their biological role or pharmacological activity. A change of this paradigm, however, is long overdue. Here, we review the current knowledge of the pharmacological activities of phyllobilins and give an overview of the diverse structural modifications, laying the groundwork for analyzing their role(s) as active components in medicinal plants.