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Refereed/Peer-reviewed Eremophila is the largest genus in the plant tribe Myoporeae (Scrophulariaceae) and exhibits incredible morphological diversity across the Australian continent. The Australian Aboriginal Peoples recognize many Eremophila species as important sources of traditional medicine, the most frequently used plant parts being the leaves. Recent phylogenetic studies have revealed complex evolutionary relationships between Eremophila and related genera in the tribe. Unique and structurally diverse metabolites, particularly diterpenoids, are also a feature of plants in this group. To assess the full dimension of the chemical space of the tribe Myoporeae, we investigated the metabolite diversity in a chemo-evolutionary framework applying a combination of molecular phylogenetic and state-of-the-art computational metabolomics tools to build a dataset involving leaf samples from a total of 291 specimens of Eremophila and allied genera. The chemo-evolutionary relationships are expounded into a systematic context by integration of information about leaf morphology (resin and hairiness), environmental factors (pollination and geographical distribution), and medicinal properties (traditional medicinal uses and antibacterial studies), augmenting our understanding of complex interactions in biological systems.

Australia’s endemic desert shrubs are commonly aromatic, with chemically diverse terpenes and phenylpropanoids in their headspace profiles. Species from the genus Eremophila (Scrophulariaceae ex. Myoporaceae) are the most common, with 215 recognised taxa and many more that have not yet been described, widely spread across the arid parts of the Australian continent. Over the years, our research team has collected multiple specimens as part of a survey to investigate the chemical diversity of the genus and create leads for further scientific enquiry. In the current study, the diversity of volatile compounds is studied using hydrodistilled essential oils and leaf solvent extracts from 30 taxa. Several rare terpenes and iridoids were detected in chemical profiles widely across the genus, and three previously undescribed sesquiterpenes were isolated and are assigned by 2D NMR—E-11(12)-dehydroisodendrolasin, Z-11-hydroxyisodendrolasin and 10-hydroxydihydro-α-humulene acetate. Multiple sampling from Eremophila longifolia, Eremophila arbuscular, Eremophila latrobei, Eremophila deserti, Eremophila sturtii, Eremophila oppositifolia and Eremophila alternifolia coneys that species in Eremophila are highly chemovariable. However, taxa are generally grouped according to the expression of (1) furanosesquiterpenes, (2) iridoids or oxides, (3) mixtures of 1 and 2, (4) phenylpropanoids, (5) non-furanoid terpenes, (6) mixtures of 4 and 5, and less commonly (7) mixtures of 1 and 5. Furthermore, GC–MS analysis of solvent-extracted leaves taken from cultivated specimens conveys that many heavier ‘volatiles’ with lower vapour pressure are not detected in hydrodistilled essential oils and have therefore been neglected in past chemical studies. Hence, our data reiterate that chemical studies of the genus Eremophila will continue to describe new metabolites and that taxon determination has limited predictive value for the chemical composition.

Mangrove forests are one of the most special forest ecosystems as a hub for marine biotope, yet they are also one of the most threatened and vulnerable ecosystems. Field investigations showed that many populations of Myoporum bontioides (Myoporaceae), a mangrove associate species recorded in southern China, southern Japan and northern Vietnam, have disappeared in China during the recent decades. For the conservation of this species and other related coastal mangrove species, we here report the genetic diversity and population structure of M. bontioides using amplified fragment length polymorphism (AFLP). The analysis produced 1557 polymorphic bands across all the 143 investigated individuals. Our results revealed a relatively high level of genetic diversity (species level: P = 98.90%, He = 0.233, I = 0.451; population level: P = 59.61%, He = 0.171, I = 0.265) and a high level of genetic differentiation (GST = 0.238 and ΦST = 0.316) in M. bontioides. No correlation was observed between genetic distances and geographic distances. A mixed mating system and limited long-distance dispersal ability may partially account for the genetic differentiation. UPGMA dendrogram, PCoA and STRUCTURE analysis revealed a distinct structure of M. bontioides populations. These findings underline that populations of M. bontioides should be preserved in situ, and the Gaoqiao and Taiwan populations should be prioritized for conservation.

The aerial parts of the endemic Australian plant Eremophila debilis (Myoporaceae) contain 3% dry weight of the biologically active 5,6,7,3',4',5'-hexamethoxyflavone, which had its structured confirmed using X-ray crystal crystallography. The presence of significant levels of the polypharmacologically active 5,6,7,3',4',5'-hexamethoxyflavone in the edible parts of the plant has potential implications for its use as a food and bush medicine.

Leaves of five selected plants Citrus limon (Rutaceae), Ceratonia siliqua L., Olea europaea (Oleaceae), Washingtonia filifera, and Myoporum (Myoporaceae) grown in Jordan were examined for removal of heavy metals (cadmium (Cd) and lead (Pb) ions) for aqueous solutions. Cd and Pb were analyzed by atomic absorption spectrometry. A pH S-2 acidometer was used for determining the acidity of leaves–solution systems. Results indicated that those plant leaves were efficient for removal of metals compared with the efficiency of activated carbon. Removal of a 5 mg/L aqueous metal solution of Cd and Pb was treated with 2.5 g of oven-dried plant in 50 mL deionized water. The metal removal was expressed as a function of time ranging between 0 and 192 h of contact time. The uptake of Cd and Pb by leaves of the plants was arranged in the following order: (i) for Cd, activated carbon > Olea europaea (Oleaceae) > Ceratonia siliqua L. > Washingtonia filifera > Citrus limon (Rutaceae) > Myoporum (Myoporaceae); (ii) for Pb, activated carbon > Olea europaea (Oleaceae) > Ceratonia siliqua L. > Washingtonia filifera > Citrus limon (Rutaceae) > Myoporum (Myoporaceae).

Myoporum is an Australian genus of family Myoporaceae widely cultivated in Libya as an ornamental plant. The hydrodistilled essential oil of fresh Libyan Myoporum acuminatum R. Br fruits (1.2%) was analyzed by GC-MS. Twenty nine constituents were identified. The oil was characterized by high content of oxygenated compounds (60.83%) mainly sesquiterpenes. The major monoterpenoids were D-limonene (34.10%) and (-) carvone (11.76%) while negaione (20.5%) and myomontanone (8.5%) were major furanoid sesquiterpenes. The antimicrobial screening showed that essential oil of this plant has promising antimicrobial activity against a number of tested microorganisms: Gram positive bacteria: Streptococcus pneumonia, Bacillis subtilis, Gram negative bacteria as Escherichia coli and certain fungi named Geotricum candidum, Aspergillus fumigates,Syncephalastrum racemosum

El concepto de especies bandera ha sido empleado en proyectos de conservación por 50 años. Se proponen aquí cinco especies nativas de la Isla de San Andrés como especies bandera para la conservación de los pocos remanentes de manglar en esta Isla: Bontia daphnoides (Myoporaceae), Canella winterana (Canellaceae), Eustoma exaltatum (Gentianaceae), Rhabdadenia biflora (Apocynaceae) y Selenicereus grandiflorus (Cactaceae). Cuatro de estas especies son documentadas aquí por primera vez para el Archipiélago, y tres representan los primeros reportes para la Flora de Colombia, dos de ellos (Canellaceae y Myoporaceae) a nivel de familia.

Myoporum bontioides A. Gray (Myoporaceae), a red list plant in Japan, is restricted to only a few East Asian countries like China, Japan and Taiwan, associated to some true mangroves. The leaf is isolateral and has a thick cuticle; stomata are anomocytic, sunken and have a beak-shaped cuticular outgrowth at the inner and outer side of the stomatal pore (ledges); profuse glandular hairs are scattered on both leaf surfaces of young leaves. The mesophyll is compact with palisade and spongy parenchyma cells in the young stage, but at maturity profuse intercellular spaces can be observed. Secretory ducts occur in young leaves. Pear-shaped glandular hairs protrude from the epidermal layer. Hair primordia are well distinct by their larger size and undergo divisions to produce two laterally placed basal cells, two stalk cells and four radiating terminal cells. The cuticle layers of the terminal cells are often separated from the cell wall to form a space, in which ions accumulate for excretion. Inner walls of the basal cells are connected with the mesophyll. Though ontogeny and structure of glandular hairs have resemblance to typical mangroves, considering leaf micromorphology, this plant is better termed as “mangrove associate” instead of “true man

Myoporum bontioides is a traditional medicinal plant in Asia with various biological activities, including anti-inflammatory and anti-bacterial characteristics. To identify the bioactive constituents from M. bontioides, a newly-identified flavone, 3,4′-dimethoxy-3′,5,7-trihydroxyflavone (compound 1), along with eight known compounds, were investigated in human MCF-7 breast cancer, SCC4 oral cancer, and THP-1 monocytic leukemia cells. Among these compounds, compound 1 exhibited the strongest antiproliferative activity with half-maximal inhibitory concentration (IC50) values ranging from 3.3 μM (MCF-7) to 8.6 μM (SCC4). Flow cytometric analysis indicated that compound 1 induced G2/M cell cycle arrest in MCF-7 cells. Mechanistic evidence suggests that the G2/M arrest could be attributable to compound 1’s modulatory effects on the phosphorylation and expression of numerous key signaling effectors, including cell division cycle 2 (CDC2), CDC25C, and p53. Notably, compound 1 downregulated the expression of histone deacetylase 2 (HDAC2) and HDAC4, leading to increased histone H3 acetylation and p21 upregulation. Together, these findings suggest the translational potential of compound 1 as a breast cancer treatment.

A detailed investigation of the wood, leaf, branch and root oil of Eremophila mitchellii (Benth.) was carried out by a combination of GC-FID, GC-MS and NMR. The wood oil was composed predominantly of eremophilanes, a rare class of biologically active, bicyclic sesquiterpenoids. The root oil was also found to contain the eremophilanes together with the zizaene sesquiterpene, sesquithuriferone. 9-Hydroxy-1,7(11),9-eremophilatrien-8-one and the known 1(10),11-eremophiladien-9-one (eremophilone), 9-hydroxy-7(11),9-eremophiladien-8-one (2-hydroxyeremophilone), 8-hydroxy-11-eremophilen-9-one (santalcamphor), 8-hydroxy-10,11-eremophiladien-9-one, sesquithuriferone and 8-hydroxy-1,11-eremophiladien-9-one were purified and elucidated by NMR. Three approaches to the purification of the major eremophilanes from the wood oil are described. (+) Spathulenol, α-pinene, globulol, viridiflorene were the major constituents of the leaf oil. All of the essential oils and the eremophilanes exhibited cytotoxicity against P388D(1) mouse lymphoblast cells in-vitro.

Myoporum semotum is described as a new species from the Chatham Islands, New Zealand, where it is known from Pitt Island, and the neighbouring South East, Rabbit, Mangere and Little Mangere islands. Notably, it is absent from Chatham Island where only Myoporum laetum occurs. Myoporum semotum is a coastal species occurring mostly in forest habitats but also in wind-shorn coastal shrubland. This new species is distinguished from M. laetum by its smoother bark, usually wider leaves, the leaf secretory cavities being obscure, smaller and dense, the midrib, petioles and branchlets being smooth and lacking prominent protruding tubercules, and in having slightly larger flowers. The conservation status of M. semotum is assessed as Nationally Vulnerable as it is currently known from between 1000 and 5000 mature plants.

Volatile oils of Eremophila longifolia F. Muell. (Myoporaceae) leaves were obtained by hydrodistillation and analysed using GC-MS. A total of 33 compounds were identified in the oils examined and a high degree of intraspecific variability in chemical composition between specimens occurring in separate geographic localities was found. Multivariate statistical analysis of chemical composition of volatile oils enabled classification of three chemotypes in this species.

Thirty-eight microsatellite loci were developed for the bird pollinated, autohexaploid, Eremophila glabra ssp. glabra. A genomic library was screened with dinucleotide and trinucleotide sequence repeats. Polymorphism ranged from one to 21 alleles per locus. Twenty-four loci exhibited null alleles, based on patterns of inheritance between maternal and progeny phenotypes. Cross-species amplification of nine Eremophila species was successful for most primers, indicating wide applicability across the genus. These microsatellites will be used to study the gene flow patterns of fragmented populations of E. glabra ssp. glabra.

Sixteen compounds were isolated from the MeOH extract of leaves of Myoporum bontioides. Of the compounds isolated, five were found to be new. Their structures were elucidated to be a chlorine-containing iridoid, named myopochlorin, and an iridoid glucoside, an acylated iridoid glucoside, a linear acetogenin glucoside, and an acyclic monoterpene glucoside, named myobontiosides A-D, respectively, by means of spectroscopic analyses.

Extracts of seventeen traditional Australian medicinal plants used to treat infections and respiratory conditions were tested for anti-mycobacterial activity against the fast-growing strains, Mycobacteriumfortuitum andM. smegmatis. Four extracts, the aerial parts of Pterocaulon sphacelatum (Asteraceae), the bark and leaves of Acacia ligulata (Mimosaceae), the leaves and stems of Eremophila alternifolia (Myoporaceae) and the leaves of Eremophila longifolia, showed activity against M. smegmatis only, while the two Eremophila extracts were also active against M. fortuitum. The minimum inhibitory concentrations ranged from 20-66 mg mL -1. The identification of the anti-mycobacterial compounds from these extracts may yield new and effective agents to combat diseases caused by Mycobacterium species.

We report a search for antimicrobial compounds in the Australian plant Eremophila serrulata . Bioassay directed fractionation of a diethyl ether extract prepared from the leaves of E. serrulata led to the isolation of two compounds, an ο -naphthoquinone, 9-methyl-3-(4-methyl-3-pentenyl)-2,3-dihydronaphtho[1,8- bc ]pyran-7,8-dione ( 2 ), and a serrulatane diterpenoid, 20-acetoxy-8-hydroxyserrulat-14-en-19-oic acid ( 3 ). Two other known serrulatane-type diterpenoids, 8,20-dihydroxyserrulat-14-en-19-oic acid ( 4 ) and 8,20-diacetoxyserrulat-14-en-19-oic acid ( 5 ) were also isolated. None of these compounds had previously been tested for antimicrobial activity. Compounds 2 – 5 showed antimicrobial activity against Staphylococcus aureus (ATCC 29213) with minimum inhibitory concentrations (MICs) ranging from 15.6 to 250 μg/mL. Compound 2 was the most active with an MIC of 15.6 μg/mL and a minimum bactericidal concentration (MBC) of 125 μg/mL. This compound also showed antimicrobial activity against other Gram-positive bacteria including Streptococcus pyogenes , and Streptococcus pneumoniae . No activity was observed for this compound against all Gram-negative bacteria tested.

This paper reports on the isolation and identification of antibacterial constituents from the indigenous Australian medicinal plant Eremophila duttonii F. Muell. (Myoporaceae). Preparations derived from this plant are used by indigenous populations in the topical treatment of minor wounds, otitis and ocular complaints, and as a gargle for sore throat. Several authors have reported extracts of this plant to effect rapid bacteriolysis and inhibit growth of a wide range of Gram-positive micro-organisms. In other studies involving screening of native medicinal plants for antibacterial activity, extracts of Eremophila duttonii have been reported to consistently exhibit the highest potency amongst all species included. From a hexane extract, we identified two diterpenes of the serrulatane class, the principal constituents responsible for antibacterial activity and present as major constituents of the resinous leaf cuticle: serrulat-14-en-7,8,20-triol (1) and serrulat-14-en-3,7,8,20-tetraol (2). In addition, a hydroxylated furanosesquiterpene with mild antibacterial activity which appeared to be a novel compound was isolated from the extract and tentatively identified as 4-hydroxy-4-methyl-1-(2,3,4,5-tetrahydro-5-methyl[2,3'-bifuran]-5-yl) pentan-2-one. Minimum inhibitory concentrations for each of the compounds against three Gram-positive bacteria: Staphylococcus aureus (ATCC 29213), Staphylococcus epidermidis (ATCC 12228) and Streptococcus pneumoniae (ARL 10582), were determined using a micro-titre plate broth dilution assay.

Two serrulatane diterpenes, 3,8-dihydroxyserrulatic acid (1) and serrulatic acid (2), have been isolated from Eremophila sturtii through bioassay-guided fractionation. These compounds inhibit the inflammation pathway enzymes cyclooxygenase 1 and 2, and exhibit bactericidal activity against Staphylococcus aureus.

The potential of the leaf beetle Charidotis auroguttata as a biocontrol agent for cat’s claw creeper Macfadyena unguis-cati (Bignoniaceae), an environmental weed in Australia, and risk to non-target plants was evaluated under quarantine conditions. In no-choice tests, C. auroguttata adults and larvae fed on many plant species across different families, but egg to adult development occurred only on the target weed. However, when neonate larvae from the target weed were transferred onto Myoporum boninense australe (Myoporaceae), a non-target native plant, 11.7% completed development, as compared to 95% of larvae that completed development on the target weed. Larval development on this non-target species also took twice as long as on the target weed. No larvae completed development on other test plants. In choice tests, leaf area consumption by adults and larvae was significantly more on the target weed than on other plants, and oviposition occurred only on the target weed. In the no-choice demography trials, adults laid eggs from the second week after emergence on the target weed, with an average of 0.286 eggs/female/day, resulting in an 18-fold increase in the adult population over 16 weeks. On My. boninense australe adult survival remained high, but oviposition commenced only from the 10th week after emergence with an average of 0.023 eggs/female/day, and none of the eggs developed into adults. In the choice demography trials, oviposition on the target weed was evident from the fourth week onwards, while on the non-target plant oviposition commenced only from the 14th week. Only 10% of total adults and 11.3% of total eggs were found on the non-target plant, and none of these eggs developed into adults. Although the biocontrol agent can ‘spill-over’ from the target weed to the non-target native plant and cause adult feeding damage, the non-target plant could not sustain a viable insect population on its own. This agent was not approved for field release in Australia due to perceived risk to non-target species.

Ethanolic extracts of five traditional Australian medicinal plants, previously shown to display antibacterial activity against laboratory strains of the Gram positive bacteria Staphylococcus aureus and Enterococcus faecalis, were investigated for their abilities to inhibit clinical isolates of methicillin-resistant Staphylococcus aureus (MRSA) and vancomycin-resistant enterococci (VRE). Using plate-hole diffusion assays, the following results were obtained: (a) extract from the leaves of Eremophila alternifolia (Myoporaceae) showed activity against MRSA; (b) extract from the leaves of Acacia kempeana (Mimosaceae) showed incomplete inhibition of VRE; (c) extracts from the leaves of Amyema quandong (Loranthaceae) and Eremophila duttonii (Myoporaceae) were active against both types of bacteria; (d) extract from the stem base of Lepidosperma viscidum (Cyperaceae) was active against MRSA and exhibited incomplete inhibition of VRE. All active extracts were evaluated using time-kill assays. Most of the extracts showed bactericidal effects and reduced the number of viable cells by 4-6 logs within four hours, while the extracts from Acacia kempeana leaves and Lepidosperma viscidum stem base exhibited bacteriostatic activity against VRE. The extract from the leaves of Eremophila duttonii was the most active and reduced the number of viable cells of MRSA and VRE to undetectable levels within 1 hour.

Background: Five plants used traditionally by Australian Aboriginals and two edible native Australian fruits have been investigated for anticancer activity. The aim was to identify native Australian herbal medicines which displayed anticancer activity, with cytotoxicity to cancer cells but sparing or even proliferating normal immunological cells, and subsequently provide potentially new anticancer drug leads. Methods: Extracts and derived fractions were assayed for cell viability against a multiple myeloma cell line, RPMI-8226, in comparison to the peripheral blood mononuclear cells (PBMC) representing normal human immunological cells. Results: None of the crude extracts exhibited the desirable differential activity; however, following further fractionation of the Eremophila duttonii F. Muell. (Myoporaceae) extract, one fraction (termed F01) exhibited a greater cytotoxicity to the cancer cell line than to the normal cells. Conclusions: One fraction may potentially contain valuable compounds which may be useful for further investigation. This may focus on the identification of the bioavailable purified compounds present within these fractions or by detailed delineation of the related mechanisms of action.

Conspicuous air spaces in Leucophyllum (Scrophulariaceae; Leucophylleae) leaves have been suggested to be developmentally transformed secretory cavities. We reinvestigated air space development in Leucophyllum frutescens, using freehand sections of mature fresh leaves and paraffin sections of several leaf stages. Each of the numerous air spaces per leaf forms because greater separation occurs within a local group of spongy mesophyll cells than in the developing spongy mesophyll elsewhere. We found no anatomical evidence of transitory epithelial cells or lysis of cells in developing air spaces, thus the hypothesis that air spaces are transformed secretory cavities is not supported. However, an important finding was that all leaves had one pair of conspicuous true secretory cavities flanking the midvein at the apex, each lined by an epithelium and filled with oil. We also found conspicuous apical cavities in freehand sections of herbarium specimens of this and three other Leucophyllum species. Cavities were not seen in L. revolutum or in the related Eremogeton grandiflorus. This is the first report and description of a true internal secretory cavity in Scrophulariaceae. In the related family Myoporaceae, we found epithelium-lined cavities scattered abundantly in leaves of cleared samples of three genera.

Extracts of 40 different plant species used in the traditional medicine of the Australian Aboriginal people have been investigated for antiviral activity. The extracts have been tested for activity against one DNA virus, human cytomegalovirus (HCMV) and two RNA viruses, Ross River virus (RRV) and poliovirus type 1, at non-cytotoxic concentrations. The most active extracts were the aerial parts of Pterocaulon sphacelatum (Asteraceae) and roots of Dianella longifolia var. grandis (Liliaceae), which inhibited poliovirus at concentrations of 52 and 250 microg/ml, respectively. The extracts of Euphorbia australis (Euphorbiaceae) and Scaevola spinescens (Goodeniaceae) were the most active against HCMV. Extracts of Eremophila latrobei subsp. glabra (Myoporaceae) and Pittosporum phylliraeoides var. microcarpa (Pittosporaceae) exhibited antiviral activity against RRV.

Four iridoid glycosides isolated from different species of Eremophila (Myoporaceae) were tested for their effects on the Langendorff rat heart. Melampyroside (1), verminoside (2), ferruloylajugol (3) and catalpol (4) all significantly decreased contractile force in the isolated rat heart test. Within a minute after administration all, except catalpol, significantly increased heart rate and coronary perfusion rate. These results are compared to those of other cardioactive iridoid glycosides described in the literature.

Summary Activity directed isolation studies of the ethanol extract of Bontia daphnoides L (Myoporaceae) leaves and stems led to the isolation of epingaione, a sesquiterpene furan. This compound was previously described by Chinnock et al. (1987) from the same plant. The compound showed growth regulatory activities on gravid adult female Boophilus microplus Canestrini (the southern cattle tick). The dose required for inhibiting the hatching of B. microplus eggs by 50% (Fid50)was 0.4±0.06 mg/g of the tick body weight. The Fid50 dose inhibited the sequestration of protein into eggs oviposited by 80%. These eggs were non-agglutinated and wrinkled. Histological examination of ovarian sections from the treated ticks revealed significant degeneration of funicle cells and reduction in yolk content.

The isolation and identification of two cardioactive compounds from two Eremophila species (Myoporaceae) considered important in the pharmacopoeia of the Australian Aboriginal people is described. Verbascoside, isolated from the methanol and water extracts of E. alternifolia leaves, mediated significant increases in chronotropism, inotropism and coronary perfusion rate (CPR) in the Langendorff rat heart. Geniposidic acid, isolated from the methanol extract of E. longifolia leaves, mediated an inhibitory effect with significant negative chronotropism, negative inotropism and CPR.