- Title
- Pre-treatment, extraction and encapsulation of the Australian maroon bush (Scaevola spinescens R. Br.) extract enriched with bioactive compounds
- Creator
- Nguyen, Kien Q.
- Relation
- University of Newcastle Research Higher Degree Thesis
- Resource Type
- thesis
- Date
- 2021
- Description
- Research Doctorate - Doctor of Philosophy (PhD)
- Description
- Scaevola spinescens R. Br. is endemic to Australia and traditionally used by Aboriginal and Torres Strait Islander communities as a medicinal plant. Because of its long history of therapeutic use there is growing research interest on the bioactive properties of the plant, as well as an emerging market for its use by health practitioners as a natural product. Our review (Chapter 2) highlights recent studies that link S. spinescens extracts with various medicinal properties including antiviral, antibacterial, anticancer, and anti-inflammatory activities. These studies not only support the ethnopharmacological use of the plant by Aboriginal and Torres Strait Islander communities, but highlight its potential for use in food and pharmaceutical applications. Although there has been some recent work investigating its therapeutic benefits, the plant remains largely underutilised. Therefore, ongoing assessment of the phytochemistry and post-harvest treatment of the plant is warranted. This study aimed to identify the most suitable conditions for pre-treatment, extraction and encapsulation of the S. spinescens extract by evaluating: (1) the effects of different drying conditions of plant material; (2) the phytochemical composition from various parts of the plant; (3) the optimal extraction conditions, and finally; (4) the optimal encapsulation conditions of the extract, for further use in food and pharmaceutical applications. This study found that different drying conditions significantly affected total phenolic content (TPC), flavonoids, saponins and antioxidant activity (Chapter 4). Microwave irradiation at 240 W retained the highest levels of total phenolics (45.82 mg GAE/g), whereas hot air drying at 110 °C and vacuum oven drying at 90 °C retained the highest levels of saponins (150.72 mg ESE/g and 146.61 mg ESE/g, respectively) and antioxidant activity. Per KWh of energy consumed, microwave drying at 240 W for 600 s had dramatically higher yields than all other methods tested (~4700 times more efficient than freeze drying and ~66 times more efficient than hot air or vacuum oven drying), and therefore, is recommended for cost-effective drying of S. spinescens. The drying conditions that retained highest levels of phenolics, saponins and antioxidant activity was then used to determine the phytochemical concentrations in different parts of the plant (Chapter 5). This study found that the bioactives and antioxidant properties, as well as major individual phytochemical compounds differed among the whole root, root bark, root wood, whole stem, stem bark, stem wood, and leaf of S. spinescens. The leaf possessed significantly higher concentrations of TPC followed by the root bark and stem bark (47.34, 12.24 and 10.20 mg GAE/g, respectively). Flavonoids concentrations were also significantly higher in the leaf compared to the root bark and stem bark (20.95, 6.22 and 4.19 mg CE/g, respectively). For saponins, the root bark contained significantly highest concentrations (112.58 mg EE/g). Luteolin 7-glucoside was isolated and identified in the leaf of S. spinescens. Eight major compounds were identified with the leaf displaying the highest diversity of major compounds, and in higher concentrations, compared to the other plant constituents. As the leaf contained the highest concentrations and diversity of phytochemicals, only the leaf material was used for further investigation to determine optimal aqueous extraction conditions. To determine the optimal aqueous extraction conditions, response surface methodology (RSM) was used to evaluate the influence of four independent parameters including temperature, time, sample-to-water ratio and pH (Chapter 6). The RSM models showed that extraction temperature, time and sample-to-water ratio significantly affected TPC yield. Temperature and time significantly affected flavonoid yields, while saponins were only significantly affected by sample-to-water ratio. Extraction temperature and time had a greater influence on extraction efficiency of TPC and flavonoids than water pH. Sample-to-water ratio had the greatest influence on extraction efficiency of saponins than all other extraction parameters. Optimal conditions for extraction were determined to be a temperature of 90 ºC, time of 53 min, sample-to-water ratio of 2:100 (g/mL) and pH of 4.5, if saponins are the target compound for extraction. For more cost effective extraction of TPC, flavonoids and antioxidant capacity, these optimal conditions are also recommended but with a higher sample-to-water ratio of 6:100 (g/mL). Following optimised extraction, encapsulation of the extract is required to improve physicochemical properties and widen its scope in food and pharmaceutical applications. This study found that different spray drying conditions and carrier materials significantly influenced the physicochemical and antioxidant properties of S. spinescens extract (Chapter 7). Carrier material concentrations had significant impacts on TPC, flavonoids, saponins, as well as antioxidant properties of the powder. Increasing carrier material concentration decreased recovery yield and increased moisture content. Inlet air temperature significantly affected recovery yield, moisture content, water activity, bulk density and colour attributes of the powder. Feed rate had significant impacts on the physical properties of powder, with higher TPC observed at lower feed rates. The type of wall material significantly affected TPC, flavonoids, and saponins, as well as antioxidant properties. Samples using whey protein had highest concentrations of TPC, but also lowest levels of flavonoids and recovery yield. Samples using acacia gum displayed highest concentrations of saponins. Whey protein showed significantly higher moisture content and conversely, low hygroscopicity. Maltodextrin of dextrose equivalent 4, 10 and 18 also showed low hygroscopicity, as well as high recovery yields. Overall, the most suitable encapsulating conditions were recommended as a carrier material concentration of 10 g/100 mL, inlet air temperature of 140 °C, feed rate of 12 mL/min, and with carrier material consisting of maltodextrin (dextrose equivalent 10 or 18) for overall encapsulation performance, or acacia gum for maximum retention of TPC and saponins. Encapsulated powder prepared using these conditions produces an optimal product with strong physical, phytochemical and antioxidant properties allowing for further utilisation in food or pharmaceutical applications. Future studies are recommended to further test and apply these encapsulated extracts as functional ingredients or in health supplements. Future studies are also needed to isolate and identify individual compounds, in order to better understand their modes action. Isolation of these molecules could potentially lead to compounds for synthetic antimicrobial and anticancer drugs. Further investigation on the individual compounds and their synergistic effects against extensive panels of microbial agents and different types of cancers at different levels is also warranted, to verify the suitability of these products for food and pharmaceutical applications.
- Subject
- scaevola spinescens; maroon bush; optimisation; response surface methodology; thesis by publication; ethnopharmacology; phytochemicals; antioxidants; bioactive compounds; plant parts; drying; extraction; encapsulation
- Identifier
- http://hdl.handle.net/1959.13/1513896
- Identifier
- uon:56778
- Rights
- Copyright 2021 Kien Q. Nguyen
- Language
- eng
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