Nomenclatural changes in Coleus and Plectranthus (Lamiaceae): a tale of more than two genera

Plant In Vitro Cultures of Coleus scutellarioides (L.) Benth. "Electric Lime" and Possibilities of Modification in the Biosynthesis of Volatile Compounds

Coleus scutellarioides (L.) Benth. is a globally spread species, known for its characteristic spectacularly colorful leaves of decorative value. Thanks to its rich chemical composition, the plant is used in ethnopharmacology, and it is also regarded as having high medicinal potential. The application of in vitro cultures enables the acquisition of homogeneous certified material of high quality. Additionally, excluding the effect of biotic and abiotic factors on the plants is a way to fully recognize the influence of phytohormones on the plant morphology and the biosynthetic pathways of compound production. The best way to grow C. scutellarioides "Electric Lime" under in vitro conditions is to use the basic MS medium (Murashige and Skoog medium), enriched with naphthyl-1-acetic acid at a concentration of 0.5 mg dm-3. The analysis of volatile compounds demonstrated that the content of volatile compounds in the plants cultivated under in vivo conditions was expressed at a level of 2848.59 µg g-1, whereas in the plants bred in vitro without supplementation with phytohormones, the level was 8191.47 µg g-1. The highest content was noted for copaene, α-pinene, 1-octene-3-ol, α-selinene, sabinen, γ- and δ-cadinene, 3-octanol, and β-pinene. Aroma profiling revealed a lack of boranyl acetate, 2-hexenal, and 2-hexen-1-ol in the plants cultivated under in vivo conditions. Differences were found in the volatile composition between plants bred in vivo and in vitro, with the most significant recorded for the contents of 1-octen-3-ol and 3-octanol. The addition of plant growth regulators into the basic medium under in vitro conditions affected the percentage ratio and contents of specific compounds in plant tissues. The most intense biosynthesis of volatile compounds took place in the plants cultivated on the medium enriched with NAA at 10,579.11 µg g-1, whereas the least intense was noted for plants cultivated on the medium supplemented with BA, where it was recorded at the level of 5610.02 µg g-1. So far, there has been no research published which would pertain to the profiling of volatile compounds performed using the SPME (solid-phase microextraction) technique. Moreover, the very few studies conducted on the chemical composition of these compounds do not mention the specific variety of C. scutellarioides under analysis.

Biological Activity of 6,7-Dehydroxyroyleanone and Derivatives Obtained from Plectranthus aliciae (Codd) A.J.Paton

The Plectranthus genus (Lamiaceae) is known to be rich in abietane diterpenes. The bioactive 6,7-dehydroxyroyleanone (DHR, 1) was previously isolated from Plectranthus madagascariensis var. madagascariensis and var. aliciae. This study aimed to explore the occurrence of DHR, 1, in P. aliciae and the potential bioactivities of new semisynthetic derivatives from DHR, 1. Several extraction methods were evaluated, and the hydrodistillation, using a Clevenger apparatus, afforded the highest yield (77.8 mg/g of 1 in the essential oil). Three new acyl derivatives (2-4) were successfully prepared from 1 (yields of 86-95%). Compounds 1-4 showed antioxidant activity, antibacterial effects, potent cytotoxic activity against several cell lines, and enhanced anti-inflammatory activity that surpassed dexamethasone (positive control). These findings encourage further exploration of derivatives 2-4 for potential mechanisms of antitumoral, antioxidant, and anti-inflammatory capabilities, studying both safety and efficacy.

Diterpenes Isolated from Three Different Plectranthus Sensu Lato Species and Their Antiproliferative Activities against Gynecological and Glioblastoma Cancer Cells

Fourteen diterpenes were isolated from methanol extracts of the aerial parts ofColeus comosus,Coleus forsteri "Marginatus", and Plectranthus ciliatus. The compounds belong to the abietane (1-4, 9-11, and 13), ent-clerodane (5-8), and ent-kaurane (14, 15) classes. Three new compounds were isolated from C. comosus, including 3-O-acetylornatin G (2), 3,12-di-O-acetylornatin G (3), ornatin B methyl ester (5), and ornatin F (4), for which we proposed a revised structure. The structures of the compounds were determined by comprehensive spectroscopic data analysis. The isolated diterpenes were examined in silico for their physicochemical and early ADME properties. Their antiproliferative effects were determined in vitro using human breast (MDA-MB-231 and MCF-7), cervical (HeLa), and glioblastoma (U-87 MG) cancer cell lines. The royleanone- and hydroquinone-type abietane diterpenes (9-13)exhibited the most potent antiproliferative activity against all cancer cell lines tested, particularly against glioblastoma cells, with IC50 values ranging from 1.1 to 15.6 μM.

The influence of cultivation conditions on the formation of psychoactive salvinorin A, salvinorin B, rosmarinic acid and caffeic acid in Coleus scutellarioides

Coleus scutellarioides (L.) Benh. is a popular species in the world, known for its characteristic magnificent colourful leaves. The study has revealed that the contents of rosmarinic acid and caffeic acid are significantly higher in the plant tissues cultivated in vivo than when under in vitro conditions. The performed qualitative and quantitative analyses confirmed the presence (whose averaged content) of salvinorin A (6.65 µg/1 g of fresh plant) and salvinorin B (50.46 µg/1 g of fresh plant) in tissues of Coleus scutellarioides (L.) Benh. of 'Electric lime' variety. The greatest quantities of these compounds were recorded for plants cultivated in vitro on the MS medium enriched with NAA (naphthyl-1-acetic acid) at a concentration of 0.5 mg∙ dm-3. The research detected differences in the amounts of compounds between plants grown in vivo and those cultivated in vitro. Addition of plant growth regulators into the breeding medium under in vitro conditions was found affecting the amounts of compounds in plant tissues.

Biological Properties of Extracts Obtained from In Vitro Culture of Plectranthus scutellarioides in a Cell Model

Plectranthus scutellarioides (L.) R.Br. is a medicinal plant that has long been used in traditional medicine to treat conditions such as abscesses, ulcers, and ear and eye infections. It is known to have a wide range of biological properties, such as antibacterial, antioxidant, antifungal, anti-inflammatory, anti-diabetic and anti-cancer effects. In this study, we established in vitro cultures from both the aerial parts and roots of Plectranthus scutellarioides. Subsequently, we compared the basic phytochemical profile of the obtained extracts and conducted a biological analysis to assess their potential for inducing apoptosis in breast (MCF-7) and lung (A549) cancer cells. Phytochemical analysis by HPLC-MS revealed the presence of compounds belonging to phenolic acids (ferulic, syringic, vanillic, rosmarinic, chlorogenic, caffeic, coumaric, dihydroxybenzoic acids), flavonoids (eriodyctiol and cirsimaritin), and terpenes such as 6,11,12,14,16-Pentahydroxy-3,17diacetyl-8,11,13-abietatrien-7-one, 6,11,12,14,16-Pentahydroxy-3,17-diacetyl5,8,11,13-abietatetraen-7-one, and 3,6,12-Trihydroxy-2-acetyl-8,12-abietadien7,11,14-trione. The results show that both extracts have a cytotoxic and genotoxic effect against MCF-7 and A549 cancer cells, with a different degree of sensitivity. It was also shown that both extracts can induce apoptosis by altering the expression of apoptotic genes (Bax, Bcl-2, TP53, Fas, and TNFSF10), reducing mitochondrial membrane potential, increasing ROS levels, and increasing DNA damage. In addition, it has been shown that the tested extracts can alter blood coagulation parameters. Our results indicate that extracts from in vitro cultures of Plectranthus scutellarioides aerial parts and roots have promising therapeutic application, but further research is needed to better understand the mechanisms of their action in the in vitro model.

The CAM lineages of planet Earth

BACKGROUND AND SCOPE

The growth of experimental studies of crassulacean acid metabolism (CAM) in diverse plant clades, coupled with recent advances in molecular systematics, presents an opportunity to re-assess the phylogenetic distribution and diversity of species capable of CAM. It has been more than two decades since the last comprehensive lists of CAM taxa were published, and an updated survey of the occurrence and distribution of CAM taxa is needed to facilitate and guide future CAM research. We aimed to survey the phylogenetic distribution of these taxa, their diverse morphology, physiology and ecology, and the likely number of evolutionary origins of CAM based on currently known lineages.

RESULTS AND CONCLUSIONS

We found direct evidence (in the form of experimental or field observations of gas exchange, day-night fluctuations in organic acids, carbon isotope ratios and enzymatic activity) for CAM in 370 genera of vascular plants, representing 38 families. Further assumptions about the frequency of CAM species in CAM clades and the distribution of CAM in the Cactaceae and Crassulaceae bring the currently estimated number of CAM-capable species to nearly 7 % of all vascular plants. The phylogenetic distribution of these taxa suggests a minimum of 66 independent origins of CAM in vascular plants, possibly with dozens more. To achieve further insight into CAM origins, there is a need for more extensive and systematic surveys of previously unstudied lineages, particularly in living material to identify low-level CAM activity, and for denser sampling to increase phylogenetic resolution in CAM-evolving clades. This should allow further progress in understanding the functional significance of this pathway by integration with studies on the evolution and genomics of CAM in its many forms.

A Taxonomically-verified and Vouchered Checklist of the Vascular Plants of the Republic of Guinea

The Checklist of the Vascular Plants of the Republic of Guinea (CVPRG) is a specimen-based, expert-validated knowledge product, which provides a concise synthesis and overview of current knowledge on 3901 vascular plant species documented from Guinea (Conakry), West Africa, including their accepted names and synonyms, as well as their distribution and status within Guinea (indigenous or introduced, endemic or not). The CVPRG is generated automatically from the Guinea Collections Database and the Guinea Names Backbone Database, both developed and maintained at the Royal Botanic Gardens, Kew, in collaboration with the staff of the National Herbarium of Guinea. A total of 3505 indigenous vascular plant species are reported of which 3328 are flowering plants (angiosperms); this represents a 26% increase in known indigenous angiosperms since the last floristic overview. Intended as a reference for scientists documenting the diversity and distribution of the Guinea flora, the CVPRG will also inform those seeking to safeguard the rich plant diversity of Guinea and the societal, ecological and economic benefits accruing from these biological resources.

Anti-inflammatory activities of Coleus forsteri (formerly Plectranthus forsteri) extracts on human macrophages and chemical characterization

Introduction: Formerly named Plectranthus forsteri, Coleus forsteri (Benth.) A.J.Paton, 2019 is a Lamiaceae traditionally used to treat flu-like symptoms and shock-related ecchymosis, especially in the Pacific region. Few studies investigated chemical composition and anti-inflammatory potential of this plant. Method: Herein, we investigated anti-inflammatory potential of C. forsteri ethanolic (ePE) and cyclohexane (cPE) plant extract on LPS-induced human macrophages models and quantified cytokines and quinolinic acid (QUIN) as inflammatory markers. Results: Our results show that extract of ePE and cPE significantly inhibit inflammatory cytokine IL-6 and TNF-α induced by LPS on PMA-derived THP-1 macrophages. QUIN production is also diminished under ePE and cPE treatment in activated human monocyte-derived macrophages (MDMs). Seven abietane diterpenes were characterized from C. forsteri cPE including coleon U (1), coleon U-quinone (2), 8α,9α-epoxycoleon U-quinone (3), horminone or 7α-hydroxyroyleanone (4), 6β,7α-dihydroxyroyleanone (5), 7α-acetoxy-6β-hydroxyroyleanone (6) and 7α-formyloxy-6β-hydroxyroyleanone (7). Discussion: We discussed potential contributions of these molecules from C. forsteri extracts for their anti-inflammatory activities.

Phytochemical Study and Antiglioblastoma Activity Assessment of Plectranthus hadiensis (Forssk.) Schweinf. ex Sprenger var. hadiensis Stems

Glioblastoma (GB) is the most malignant form of primary astrocytoma, accounting for more than 60% of all brain tumors in adults. Nowadays, due to the development of multidrug resistance causing relapses to the current treatments and the development of severe side effects resulting in reduced survival rates, new therapeutic approaches are needed. The genus Plectranthus belongs to the Lamiaceae family and is known to be rich in abietane-type diterpenes, which possess antitumor activity. Specifically, P. hadiensis (Forssk.) Schweinf. ex Sprenger has been documented for the use against brain tumors. Therefore, the aim of this work was to perform the bioguided isolation of compounds from the acetonic extract of P. hadiensis stems and to investigate the in vitro antiglioblastoma activity of the extract and its isolated constituents. After extraction, six fractions were obtained from the acetonic extract of P. hadiensis stems. In a preliminary biological screening, the fractions V and III showed the highest antioxidant and antimicrobial activities. None of the fractions were toxic in the Artemia salina assay. We obtained different abietane-type diterpenes such as 7α-acetoxy-6β-hydroxyroyleanone (Roy) and 6β,7β-dihydroxyroyleanone (DiRoy), which was also in agreement with the HPLC-DAD profile of the extract. Furthermore, the antiproliferative activity was assessed in a glioma tumor cell line panel by the Alamar blue assay. After 48 h treatment, Roy exerted strong antiproliferative/cytotoxic effects against tumor cells with low IC₅₀ values among the different cell lines. Finally, we synthesized a new fluorescence derivative in this study to evaluate the biodistribution of Roy. The uptake of BODIPY-7α-acetoxy-6β-hydroxyroyleanone by GB cells was associated with increased intracellular fluorescence, supporting the antiproliferative effects of Roy. In conclusion, Roy is a promising natural compound that may serve as a lead compound for further derivatization to develop future therapeutic strategies against GB.

Allelopathic Properties of Lamiaceae Species: Prospects and Challenges to Use in Agriculture

Herbicide resistance due to the increasing reliance on herbicides is a near-term challenge for the world’s agriculture. This has led to a desire to develop new herbicides with a novel mode of action, to address resistance in weed species. Lamiaceae, a large dicotyledonous plant family, is very well known for the multitudinous pharmacological and toxicological properties of its member species. Moreover, many species of this family are significant for their allelopathic activity in natural and laboratory settings. Thus, plants in Lamiaceae have the potential to be sources of alternative herbicides. However, gaps in our knowledge need to be addressed prior to adopting these allelopathic activities in agriculture. Therefore, we review the existing state of knowledge about the Lamiaceae family, the reported allelopathic properties of plant extracts, and their isolated allelochemicals under laboratory, greenhouse, and field conditions. In addition, we offer a perspective on existing challenges and future opportunities for adopting the allelopathic properties of Lamiaceae plant species for green agriculture.

Abietane Diterpenes of the Genus Plectranthus sensu lato

Plectranthus (Lamiaceae), which—according to the latest systematic revision—includes three separate genera (Coleus, Plectranthus sensu stricto, and Equilabium), is a genus widely used in traditional medicine—mainly in the treatment of various ailments of the digestive tract, respiratory tract, and skin. Many species of Plectranthus s.l. have been shown to produce phenolic compounds and terpenes. Diterpenes, especially those of the abietane class, are the most studied group of secondary metabolites found in Plectranthus s.l., which is characterized by a significant structural diversity arising from the oxygenation and further rearrangement of the basic tricyclic abietane skeleton to a complete aromatization of the ring system. This review summarizes the known information on abietane diterpenes, showing their structures, sources, and biosynthesis. A classification of these compounds into nine groups, according to the arrangement of their ring C, is used. Royleanones, spirocoleons, and hydroquinones are the largest classes of abietane diterpenes, covering more than 70% of all the compounds reviewed.

 Coleus (Lamiaceae) in Peninsular Malaysia including two new species

In Peninsular Malaysia, Coleus is represented by five species. Two, C.hairulii Kiew and C.rafidahiae Kiew, are new species. Both are narrowly endemic and restricted to limestone hills as is C.kunstleri (Prain) A.J.Paton. All three are Critically Endangered. Coleusscutellarioides (L.) Benth., although widespread, is probably not indigenous. It is also a common ornamental, while C.monostachyus (P.Beauv.) A.J.Paton is a recent introduction that has spread rapidly and threatens to become a troublesome weed.

Quantitative dissection of color patterning in the foliar ornamental coleus

Coleus (Coleus scutellarioides) is a popular ornamental plant that exhibits a diverse array of foliar color patterns. New cultivars are currently hand selected by both amateur and experienced plant breeders. In this study, we reimagine breeding for color patterning using a quantitative color analysis framework. Despite impressive advances in high-throughput data collection and processing, complex color patterns remain challenging to extract from image datasets. Using a phenotyping approach called "ColourQuant," we extract and analyze pigmentation patterns from one of the largest coleus breeding populations in the world. Working with this massive dataset, we can analyze quantitative relationships between maternal plants and their progeny, identify features that underlie breeder-selections, and collect and compare public input on trait preferences. This study is one of the most comprehensive explorations into complex color patterning in plant biology and provides insights and tools for exploring the color pallet of the plant kingdom.

Differences in diterpenoid diversity reveal new evidence for separating the genus Coleus from Plectranthus

Covering: up to 2019The large and medicinally important tropical plant genus Plectranthus (Lamiaceae) was recently split into three separate genera on the basis of molecular and morphological evidence; Plectranthus sensu stricto, Coleus and Equilabium. We found striking differences between the diterpenoids which strongly support this taxonomic split. Coleus is characterised by abietanes oxygenated at C-14 such as royleanones, spirocoleons and acylhydroquinones, which could be useful chemotaxonomic markers to distinguish this genus from Plectranthus s.s. In contrast, the abietanes in Plectranthus s.s. lack C-14 oxygenation, but are often acylated with unusual acids. Equilabium species do not seem to produce diterpenoids. The structures of the nearly 240 abietanes so far reported from Coleus and Plectranthus and their distribution are presented. The aim of this Highlight is to provide an overview of the differences in diterpenoid diversity between these newly defined genera, which are relevant to predict which previously understudied species could hold untapped potential for their medicinal and other economic uses, and to underpin future research on how these plants have evolved to synthesise distinct abietane types.

The World Checklist of Vascular Plants, a continuously updated resource for exploring global plant diversity

The World Checklist of Vascular Plants (WCVP) is a comprehensive list of scientifically described plant species, compiled over four decades, from peer-reviewed literature, authoritative scientific databases, herbaria and observations, then reviewed by experts. It is a vital tool to facilitate plant diversity research, conservation and effective management, including sustainable use and equitable sharing of benefits. To maximise utility, such lists should be accessible, explicitly evidence-based, transparent, expert-reviewed, and regularly updated, incorporating new evidence and emerging scientific consensus. WCVP largely meets these criteria, being continuously updated and freely available online. Users can browse, search, or download a user-defined subset of accepted species with corresponding synonyms and bibliographic details, or a date-stamped full dataset. To facilitate appropriate data reuse by individual researchers and global initiatives including Global Biodiversity Information Facility, Catalogue of Life and World Flora Online, we document data collation and review processes, the underlying data structure, and the international data standards and technical validation that ensure data quality and integrity. We also address the questions most frequently received from users.

Measurement(s)	Vascular Plant • Species
Technology Type(s)	digital curation
Sample Characteristic - Organism	Tracheophyta
Sample Characteristic - Location	global

Machine-accessible metadata file describing the reported data: 10.6084/m9.figshare.15035046

The Botanical, Chemical and Ethnobotanical Diversity of Southern African Lamiaceae

The Lamiaceae is undoubtedly an important plant family, having a rich history of use that spans the globe with many species being used in folk medicine and modern industries alike. Their ability to produce aromatic volatile oils has made them valuable sources of materials in the cosmetic, culinary, and pharmaceutical industries. A thorough account of the taxonomic diversity, chemistry and ethnobotany is lacking for southern African Lamiaceae, which feature some of the region’s most notable medicinal and edible plant species. We provide a comprehensive insight into the Lamiaceae flora of southern Africa, comprising 297 species in 42 genera, 105 of which are endemic to the subcontinent. We further explore the medicinal and traditional uses, where all genera with documented uses are covered for the region. A broad review of the chemistry of southern African Lamiaceae is presented, noting that only 101 species (34%) have been investigated chemically (either their volatile oils or phytochemical characterization of secondary metabolites), thus presenting many and varied opportunities for further studies. The main aim of our study was therefore to present an up-to-date account of the botany, chemistry and traditional uses of the family in southern Africa, and to identify obvious knowledge gaps.

Constitutive and facultative crassulacean acid metabolism (CAM) in Cuban oregano, Coleus amboinicus (Lamiaceae)

Plants exhibiting the water-conserving crassulacean acid metabolism (CAM) photosynthetic pathway provide some of the most intriguing examples of photosynthetic diversity and plasticity. Here, a largely unnoticed facet of CAM-plant photosynthesis is highlighted: the co-occurrence of ontogenetically controlled constitutive and environmentally controlled facultative CAM in a species. Both forms of CAM are displayed in leaves of Coleus amboinicus Lour. (Lamiaceae), a semi-succulent perennial plant with oregano-like flavour that is native to southern and eastern Africa and naturalised elsewhere in the tropics. Under well-watered conditions, leaves assimilate CO2 predominantly by the C3 pathway. They also display low levels of CO2 uptake at night accompanied by small nocturnal increases in leaf tissue acidity. This indicates the presence of weakly expressed constitutive CAM. CAM expression is strongly enhanced in response to drought stress. The drought-enhanced component of CAM is reversible upon rewatering and thus considered to be facultative. In contrast to C. amboinicus, the thin-leaved closely related Coleus scutellarioides (L.) Benth. exhibits net CO2 fixation solely in the light via the C3 pathway, both under well-watered and drought conditions. However, low levels of nocturnal acidification detected in leaves and stems indicate that the CAM cycle is present. The highly speciose mint family, which contains few known CAM-exhibiting species and is composed predominantly of C3 species, appears to be an excellent group of plants for studying the evolutionary origins of CAM and for determining the position of facultative CAM along the C3-full CAM trajectory.

An updated tribal classification of Lamiaceae based on plastome phylogenomics

BACKGROUND

A robust molecular phylogeny is fundamental for developing a stable classification and providing a solid framework to understand patterns of diversification, historical biogeography, and character evolution. As the sixth largest angiosperm family, Lamiaceae, or the mint family, consitutes a major source of aromatic oil, wood, ornamentals, and culinary and medicinal herbs, making it an exceptionally important group ecologically, ethnobotanically, and floristically. The lack of a reliable phylogenetic framework for this family has thus far hindered broad-scale biogeographic studies and our comprehension of diversification. Although significant progress has been made towards clarifying Lamiaceae relationships during the past three decades, the resolution of a phylogenetic backbone at the tribal level has remained one of the greatest challenges due to limited availability of genetic data.

RESULTS

We performed phylogenetic analyses of Lamiaceae to infer relationships at the tribal level using 79 protein-coding plastid genes from 175 accessions representing 170 taxa, 79 genera, and all 12 subfamilies. Both maximum likelihood and Bayesian analyses yielded a more robust phylogenetic hypothesis relative to previous studies and supported the monophyly of all 12 subfamilies, and a classification for 22 tribes, three of which are newly recognized in this study. As a consequence, we propose an updated phylogenetically informed tribal classification for Lamiaceae that is supplemented with a detailed summary of taxonomic history, generic and species diversity, morphology, synapomorphies, and distribution for each subfamily and tribe.

CONCLUSIONS

Increased taxon sampling conjoined with phylogenetic analyses based on plastome sequences has provided robust support at both deep and shallow nodes and offers new insights into the phylogenetic relationships among tribes and subfamilies of Lamiaceae. This robust phylogenetic backbone of Lamiaceae will serve as a framework for future studies on mint classification, biogeography, character evolution, and diversification.

Notulae to the Italian alien vascular flora: 8

In this contribution, new data concerning the distribution of vascular flora alien to Italy are presented. It includes new records, confirmations, exclusions, and status changes for Italy or for Italian administrative regions of taxa in the genera Bunias, Calocedrus, Calycanthus, Celosia, Clerodendrum, Convolvulus, Crassula, Cyclamen, Datura, Dicliptera, Eragrostis, Erigeron, Gamochaeta, Gazania, Impatiens, Kolkwitzia, Leucaena, Ludwigia, Medicago, Muscari, Nigella, Oenothera, Opuntia, Paulownia, Petroselinum, Phyllostachys, Physalis, Pseudosasa, Quercus, Reynoutria, Roldana, Saccharum, Sedum, Semiarundinaria, Senecio, Sisyrinchium, Solanum, Sporobolus, Tulipa, Vachellia, Verbena, and Youngia. Nomenclatural and distribution updates published elsewhere are provided as Suppl. material 1.