Muntries Research Articles

Phytochemicals, Antioxidant Activities, and Toxicological Screening of Native Australian Fruits Using Zebrafish Embryonic Model.

Phytochemicals play a pivotal role in human health and drug discovery. The safety evaluation of plant extracts is a prerequisite to ensure that all phytochemicals are safe before translational development and human exposure. As phytochemicals are natural, they are generally considered safe, although this is not always true. The objective of this study was to investigate and compare the phytochemical composition, antioxidant potential, and safety evaluation of native Australian Muntries (Kunzea pomifera), Kakadu plum (Terminalia ferdinandiana), Davidson plum (Davidsonia) and Quandong peach (Santalum acuminatum) through the in vivo vertebrate zebrafish embryonic model. The highest total phenolic content (TPC; 793.89 ± 22.27 μg GAE/mg) was quantified in Kakadu plum, while the lowest TPC (614.44 ± 31.80 μg GAE/mg) was quantified in Muntries. Developmental alterations, mortality, and morbidity were assessed for toxicological screening of these selected native Australian fruit extracts. In this study, muntries were quantified as having the least LC50 value (169 mg/L) compared to Davidson plum (376 mg/L), Kakadu plum (>480 mg/L), and Quandong peach (>480 mg/L), which indicates that muntries extract was more toxic than other fruit extracts. Importantly, we found that adverse effects were not correlated to the total phenolic content and antioxidant potential of these native Australian fruits and cannot simply be predicted from the in vitro analysis. Conclusively, these selected native Australian fruit extracts are categorized as safe. This study could explore the use of these native Australian fruits in cosmetics, pharmaceuticals, and drug discovery.

Growth Inhibitory Properties of Kunzea pomifera F.Muell. and Podocarpus elatus R.Br. Fruit Extracts against Axillary and Foot Odour Producing Bacteria

Growth Inhibitory Properties of Kunzea pomifera F.Muell. and Podocarpus elatus R.Br. Fruit Extracts against Axillary and Foot Odour Producing Bacteria

Salinity Tolerance of Muntries (Kunzea pomifera F. Muell.), a Native Food Crop in Australia

Identifying productive food crops that tolerate moderate soil salinity is critical for global food security. We evaluate the salinity tolerance of Kunzea pomifera (muntries), a traditional Indigenous food plant that grows naturally in coastal regions of southern Australia and thrives on relatively low rainfall. A range of saline irrigation treatments were tested on four genotypes: tap water, 50, 200, 300, and 400 mm NaCl [Maarten’s Favorite (MF)] and up to 200 mm NaCl (MP1, SES2, and CJ1). After a 10-week saline irrigation treatment at 50 mm NaCl, SES2 appeared to have the highest salt tolerance of all genotypes based on no significant change in the number of secondary branches. At 50 mm NaCl, sodium accumulated significantly in roots but not the leaves of three genotypes, suggesting an active shoot exclusion mechanism. At 200 mm NaCl, plant growth decreased, Na+ and Cl− generally accumulated to significantly higher levels in leaves, compared with 50 mm NaCl, whereas potassium (K+) levels were unchanged. At high NaCl (300 and 400 mm), MF showed severe growth retardation with leaf symptoms appearing in week 9. Our results indicate that two genotypes of K. pomifera, SES2 and CJ1, are moderately salt tolerant based on modest reductions in three growth parameters at 50 mm NaCl, compared with MF and MP1. Further evaluation of the natural diversity of this species should reveal a range of diverse mechanisms of salinity tolerance thus providing a new fruit crop for moderately saline soils. Chemical names: NaCl (sodium chloride).

Genic simple sequence repeat markers for measuring genetic diversity in a native food crop: a case study of Australian Kunzea pomifera F.Muell. (muntries)

Kunzea pomifera F.Muell. (muntries) is a native food crop in Australia that produces spicy apple-flavoured berries. Orchards were established in the 1990s using a variety of wild-collected selections. No published records are currently available of formal plant breeding although the Rivoli Bay selection is the most widely planted. DNA markers are needed to reliably assess genetic diversity and validate plant selections, however genomic resources of K. pomifera are not available. Initially, based on the large MYB gene family, eight MYB gene fragments were amplified and cloned using a degenerate PCR primer strategy. Targeted amplicon sequencing was subsequently used to evaluate diversity of 19 K. pomifera plants and this revealed the presence of single nucleotide polymorphisms and simple sequence repeats (SSRs). Three genic SSR markers were developed from K. pomifera MYB gene fragments and another three genic SSRs were successfully transferred from K. pulchella (Lindl.) A. S. George. A high transfer rate (75%) was obtained due to selecting SSRs in genic regions (introns or intergenic regions) and using Eucalyptus grandis W.Hill sequences to identify conserved regions. The six SSRs were highly polymorphic with observed heterozygosity (Ho) (average Ho = 0.63) and polymorphic information content (PIC) (average PIC = 0.54). Using the six genic SSRs, 15 unique genotypes were identified from the K. pomifera collections in two orchards. Importantly, plants in a new diversity panel were genotyped and suspected mis-labeling events confirmed. The genic SSRs and approach developed will benefit marker assisted selection programs by increasing the proportion of genic markers that could be linked to important horticultural traits.

Benchmarking study of quality parameters of Rivoli Bay selection of Kunzea pomifera (muntries): A new Indigenous crop from Australia

New crops have played a significant role in the economic growth of countries around the world. Developing reliable information and knowledge of new crops is essential. Here we focus on one of 13 potential native food crops Indigenous to Australia, Kunzea pomifera L. (muntries, muntrie berries, family Myrtaceae). K. pomifera fruit is naturally sweet, palatable to “western” palates, has high levels of antioxidant compounds and has obtained high consumers’ acceptance in a range of products. However, as this is a new crop, there is limited information about the horticultural production of K. pomifera. This study was conducted to develop methods and determine benchmark values for several fundamental fruit characteristics (size, total soluble solids, moisture content and total phenolic content), using a clonally propagated selection, “Rivoli Bay”. Additionally, nutrient levels were determined and compared with three other Myrtaceae species K. ericoides, Chamelaucium spp. and Leptospermum lanigerum. Potassium and phosphorus levels in leaves sampled in 2015 were lower than in leaves sampled in November 2004 and January 2005 and the Myrtaceae species. Inadequate nutrition for these two key macronutrients may contribute to high variabilities of fruit size/100-berry weight and total phenolic content. The present study provides a critical reference point for the muntries industry regarding fruit characteristics (fruit size, total soluble solids, moisture content and total phenolic content) and macronutrients (potassium and phosphorus). The study highlights that optimal nutrition should be monitored as an integral part of new crop development to maximise potential at every step in the value chain.

Kunzea pomifera(muntries): selection validation and evaluation of important horticultural traits

The native food industry in Australia has been developed for nearly 40 years. This industry is focussed on 13 crops, including quandong and muntries (or muntrie berries). There are approximately 20 selections of muntries such as 'Rivoli Bay' and 'Maarten's Favourite'. 'Rivoli Bay', the industry standard selection, was chosen for evaluation at Mount Pleasant, South Australia, Australia from February to March 2014. Assessment was performed on five trellised 'Rivoli Bay' plants. Methods for the evaluation of muntries fruit size and fruit quality characteristics (texture, total soluble solids and total phenolic content) were developed from existing methods for other fruits. Variability between the five 'Rivoli Bay' plants was higher than expected for all assessed fruit characteristics, given that plants are clonally propagated, which is possibly due to an environmental effect. Results obtained for n=3 technical replicates produced low standard deviation suggesting the methods developed for assessing muntries fruit characteristics can be used in the future. To determine genetic diversity and identify cultivars, molecular markers are commonly used. We applied this approach to muntries and primers for moleculars were designed in introns or at intron-exon boundaries of eight Myb gene fragments that include one or two short introns. Three PCR fragments sequenced contained polymorphic sites between the selections. These polymorphisms included insertion/deletions (Indels) and a clear single-nucleotide polymorphism (SNP) where several individuals were heterozygous for the SNP. Our data suggested that heterozygosity is common in 'Rivoli Bay' as expected for a preferentially outcrossing species.

The prevention of fish spoilage by high antioxidant Australian culinary plants: Shewanella putrefaciens growth inhibition

SummaryShewanella putrefaciens is a marine bacterium and a major microbial cause of spoilage in low temperature stored seafood. A survey of fruits and culinary herbs was undertaken on Australian plants with high antioxidant capacities. Twenty‐eight extracts from thirteen plant species were investigated for the ability to inhibit S. putrefaciens growth. Of these, eight extracts (28.6%) substantially inhibited S. putrefaciens growth. The muntries (Kunzea pomifera), lemon aspen (Acronychia acidula) and desert lime (Citrus glauca) extracts were efficient anti‐S. putrefaciens agents, with MIC values ≤3000 μg mL−1. Of these, the muntries methanolic extract was the most potent growth inhibitor (MIC = 2240 μg mL−1). The aqueous desert lime extract was also an effective growth inhibitor (MIC of 3857 μg mL−1), whilst the methanolic bush tomato (Solanum aviculare), aqueous muntries and Davidson's plum (Davidsonia pruriens) extracts displayed moderate S. putrefaciens growth inhibition. All extracts were nontoxic in the Artemia fransiscana bioassay, with LC50 values (>1000 μg mL−1). Nontargeted HPLC‐QTOF mass spectroscopy (with screening against three compound databases) putatively identified twenty compounds that were present in both inhibitory muntries extracts. The low toxicity of these extracts and their inhibitory bioactivity against S. putrefaciens indicates their potential as natural fish and seafood preservatives.

Native Australian Fruit Polyphenols Inhibit Cell Viability and Induce Apoptosis in Human Cancer Cell Lines

Apoptosis is one of the most critical forms of defense against cancer, and the induction of apoptosis by dietary polyphenols represents significant potential for cancer preventive activity. The present study examined polyphenols extracted from selected native Australian fruits—Illawarra plum (Podocarpus elatus Endl., Podocarpaceae), Kakadu plum (Terminalia ferdinandiana Exell, Combretaceae), muntries (Kunzea pomifera F. Muell., Myrtaceae), and native currant (Acrotriche depressa R.Br., Epacridaceae)—for antiproliferative activity against a panel of cancer and normal cell lines. Each fruit selectively inhibited the growth of cancer cell lines in a dose-dependent manner. The mechanism of growth inhibition of the human promyelocytic leukaemia cells (HL-60) was determined to be apoptosis by morphological assessment, DNA fragmentation, flow cytometry, and caspase-3 induction. Furthermore, Kakadu plum was found to activate caspase-7, -9, and poly (ADP-ribose) polymerase (PARP), suggesting it acts via the intrinsic apoptosis pathway. The same fruit also caused direct DNA damage in colon adenocarcinoma cells (HT-29) as detected using the cytokinesis-block micronucleus cytome (CBMN Cyt) assay.

Native Australian fruit polyphenols inhibit COX-2 and iNOS expression in LPS-activated murine macrophages

Purified polyphenolic-rich extracts from four native Australian fruits, Illawarra Plum (Podocarpus elatus Endl., Podocarpaceae), Kakadu Plum (Terminalia ferdinandiana Exell, Combretaceae), Muntries (Kunzea pomifera F. Muell., Myrtaceae) and Native Currant (Acrotriche depressa R.Br., Epacridaceae), were screened for their ability to modulate anti-inflammatory activity in LPS-activated murine macrophages (RAW 264.7). The Kakadu Plum extract inhibited the expression of inducible nitric oxide synthase (iNOS), and importantly was the only fruit in this study that displayed differential inhibition of the expression of cyclooxygenase (COX)-2 but not COX-1. Illawarra Plum (COX-2 and iNOS) and Native Currant (iNOS only) also inhibited inflammatory enzymes, while Muntries exhibited none of these activities under the same conditions. All evaluated extracts inhibited the production of prostaglandin E2 and nitric oxide, suggesting the involvement of alternative pathways in their regulation for the Muntries extract. Further molecular investigations, showed that Kakadu Plum inhibited the NF-кB pathway, but not the p44/42 mitogen activated protein kinase (MAPK) pathway. Collectively, these results demonstrate potential anti-inflammatory activities of native Australian fruits, in particular Kakadu Plum, in LPS-activated murine macrophages, thus confirming the potential biological activities of these fruits.

Antioxidant and cytoprotective activities of native Australian fruit polyphenols

Four native Australian fruits, Illawarra Plum (Podocarpus elatus Endl., Podocarpaceae), Kakadu Plum (Terminalia ferdinandiana Exell, Combretaceae), Muntries (Kunzea pomifera F. Muell., Myrtaceae) and Native Currant (Acrotriche depressa R.Br., Epacridaceae) were examined for antioxidant and cellular protective activities. Each fruit showed significantly greater antioxidant activity than a blueberry (Vaccinum sp., cv. Biloxi) reference with Kakadu Plum exhibiting 13.3-fold and 2.4-fold activity of blueberry in the ferric ion reducing antioxidant power (FRAP) and oxygen radical absorbance capacity (ORAC-H) assays, respectively. A lyophilised polyphenolic-rich extract of Kakadu Plum exhibited the greatest cellular antioxidant activity (CAA assay) of 71.5μmolQE/g, and was followed by Illawarra Plum, Native Currant and Muntries (46.3, 20.0 and 14.4μmolQE/g, respectively). Polyphenolic-rich extracts of Kakadu Plum and Muntries (but not Illawarra Plum and Native Currant) extracts efficiently protected RAW 264.7 cells against hydrogen peroxide induced apoptosis in a dose-dependent manner. Kakadu Plum and Native Currant polyphenolic-rich extracts increased the Nrf2/Keap1 ratio, suggesting activation of the antioxidant response element (ARE) through the Nrf2/Keap1 complex. The results suggest Kakadu Plum exhibits the greatest antioxidant potential, exerting antioxidant activity through free radical scavenging and affecting two (Nrf2/Keap1) downstream transcription factors.

Breeding behaviour of Kunzea pomifera (Myrtaceae): self-incompatibility, intraspecific and interspecific cross-compatibility

To examine breeding system characteristics of the endemic Australian prostrate shrub Kunzea pomifera, artificial hybridisations were undertaken using thirteen different genotypes of K. pomifera, to elucidate: (1) self-incompatibility, (2) intraspecific cross-compatibility in the species and (3) interspecific cross-compatibility with each of K. ambigua and K. ericoides. K. pomifera exhibited very low self-compatibility, with the barrier to self-fertilisation being prevention of pollen-tube growth in the style or ovary. Following intraspecific pollination amongst a number of different genotypes of K. pomifera, 38.4% of pollinated flowers developed fruit; arrest of compatible pollen-tubes in the style, preventing fertilisation, contributes to the low fruit set in this species. Interspecific compatibility was examined between K. pomifera (pistillate parent) and K. ambigua (staminate parent) where seed set per pollinated flower (4.47) was not significantly different from intraspecific crosses (4.66). In crosses between K. pomifera (pistillate parent) and K. ericoides as staminate plant, 0.037% of pollinated flowers produced fruit, with 0.0075 seeds per pollinated flower. Reproductive barriers between these two species were evident in the style of K. pomifera, where the growing tips of the K. ericoides pollen-tubes swelled and ceased to grow.

Sources of Antioxidant Activity in Australian Native Fruits. Identification and Quantification of Anthocyanins

Selected native Australian fruits, muntries (Kunzea pomifera F. Muell., Myrtaceae), Tasmanian pepper berry (Tasmanian lanceolata R. Br., Winteraceae), Illawarra plum (Podocarpus elatus R. Br. ex Endl., Podocarpaceae), Burdekin plum (Pleiogynium timorense DC. Leenh, Anacardiaceae), Cedar Bay cherry (Eugenia carissoides F. Muell., Myrtaceae), Davidson's plum (Davidsonia pruriens F. Muell. var. pruriens, Davidsoniaceae), and Molucca raspberry (Rubus moluccanus var. austropacificus van Royen, Rosaceae), were evaluated as sources of antioxidants by 2,2-diphenyl-1-picrylhydrazyl and ferric reducing antioxidant power assays and compared with blueberry (Vaccinum spp. cv. Biloxi). The total reducing capacity of five fruits was 3.5-5.4-fold higher than that of blueberry, and the radical scavenging activities of muntries and Burdekin plum were 1.5- and 2.6-fold higher, respectively. The total phenolic level by Folin-Ciocalteu assay highly correlated with the antioxidant activity. Therefore, systematic research was undertaken to identify and characterize phenolic complexes. In the present study we report on the levels and composition of anthocyanins. The HPLC-DAD and HPLC/ESI-MS-MS (ESI = electrospray ionization) analyses revealed simple anthocyanin profiles of one to four individual pigments, with cyanidin as the dominating type. This is the first evaluation of selected native Australian fruits aiming at their utilization for the development of novel functional food products.

Pollen viability in Kunzea pomifera (Myrtaceae) as influenced by sucrose concentration and storage

In vitro germination of freshly collected pollen was examined for five genotypes of Kunzea pomifera in liquid media with 5% and 10% sucrose. There were no significant differences in germination level between the different sucrose concentrations for each of the genotypes. Pollen-germination levels were significantly different among genotypes, ranging from 7 to 89%. Pollen of one genotype, stored for 12 months at 4°C and 10% relative humidity, was evaluated for germination at intervals over this period, and while significant differences in the levels of pollen germination after different storage periods were found, there was no correlation between germination percentage and storage time. Pollen of the K. pomifera accession Kmt1 stored under such conditions for 370 days was used in controlled pollination with accession Kmt2, resulting in 3.4 seeds per fruit, which was significantly fewer than the 17.2 seeds per fruit when using fresh pollen.

THE ‘IDEOTYPE CONCEPT’ AND ITS APPLICATION TO THE SELECTION OF CULTIVARS OF TREES PROVIDING AGROFORESTRY TREE PRODUCTS

ABSTRACT The ideotype concept has been developed and modified for a number of different crops, including forest trees, over the last 35 years. In recent years it has been used in the domestication of agroforestry trees producing Agroforestry Tree Products (AFTPs), as an aid to the multiple-trait selection of superior trees for cultivar development. For example in west and central Africa, ‘fruit’ and ‘kernel’ ideotypes have been identified in lrvingia gabonensis (Bush Mango), based on quantitative characterisation of a number of fruit, nut and kernel traits. Subsequently, recognising the opportunity to develop different markets for the commercially important kernels, the ‘kernel ideotype’ has been subdivided into ‘oil’ and ‘food-thickening’ ideotypes, with options for further subdivision of the latter into ideotypes with either high viscosity or high drawability characteristics. Similar opportunities for the development of single-purpose cultivars from multi-purpose species have been identified in Sclerocarya birrea (Marula), indicating that with increasing information about the variability of AFTP's it is possible to develop a hierarchy of different ideotypes to meet different market opportunities. In S. birrea and Dacryodes edulis, future options exist to extend ideotypes with recognition of the variability in both nutritional and organoleptic qualities. In Australia, a very broad-based ideotype has been developed for the indigenous shrub Kunzea pomifera (Muntries) established on both morphological and physiological traits. Similar approaches are identified for timber trees (e.g. Triplochiton scleroxylon) and those like Santalum austrocaledonicum producing essential oils. It is concluded that ideotypes are a useful tool for visualising and conceptualising how to combine specific rare combinations of visible and invisible traits, aimed at the maximisation of Harvest Index, even when the traits are only weakly related.

Horticultural development of Australian native edible plants

The Australian native edible plant industry is rapidly expanding. We provide a review of the horticultural research that has been carried out on the top 14 commercially significant Australian native edible plants; Acacia spp. Miller (wattle), Acronychia acidula F.Muell. (lemon aspen), Backhousia citriodora F.Muell. (lemon myrtle), Eremocitrus glauca (Lindl.) Burkill (desert lime) and Microcitrus spp. Swingle (native lime), Hibiscus heterophyllus Vent. and Hibiscus sabdariffa L. (rosella), Kunzea pomifera F.Muell. (muntries), Podocarpus elatus R.Br. ex Endl. (Illawarra plum), Prostanthera spp. La Billardiere (native mint), Santalum acuminatum R.Br. (quandong), Solanum centrale Black (bush tomato), Syzygium leuhmannii F.Muell. (riberry), Tasmannia spp. R.Br. (native pepper), Terminalia ferdinandiana (= T. latipes Benth. subsp. psilocarpa Pedley) (kakadu plum) and Tetragonia tetragonioides (Pallas) Kuntze (warrigal greens). The research on most of these species has focused on propagation, breeding, cultivation, nutritional value and the isolation of natural products. On none of the species has research been completed in all these areas, and three species have no research published on them. We describe horticultural research on two other commercial species, Backhousia anisata Vickery (aniseed myrtle) and Davidsonia pruriens F.Muell. var. pruriens and var. jerseyana (Davidson’s plum), and one species with commercial potential, Pringlea antiscorbutica R.Br. ex Hook.f. (kerguelen cabbage). We identify areas that require further research and issues of concern, such as indigenous intellectual property rights and environmental implications.