Scaevola spinescens is a native Australian plant that has traditionally been used for medical purposes. This study aimed to determine the impact of different drying conditions on the bioactive compound yield and antioxidant activity in dried S. spinescens. The results showed that different drying conditions significantly affected total phenolics, flavonoids, saponins and antioxidant activity. 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 (~4,700 times more efficient than freeze drying and ~66 times more efficient than hot air or vacuum oven drying), and therefore is recommended for drying S. spinescens.
Practical applications
Drying is an important step in tea production, and also to prepare starting materials for further processing. However, the drying process can affect the retention of desired compounds and is closely associated with production costs. This study revealed that inappropriate drying conditions can negatively impact the retention of bioactive compounds and antioxidant activity of Scaevola spinescens. Furthermore, we consider recovery yields with respect to power consumed, and found that microwave irradiation at 240 W for 600 s to be the most energy efficient drying method. Microwave irradiation is also the fastest method of drying and can be easily applied to dry S. spinescens on a commercial scale.
Scaevola spinescens is endemic to Australia and traditionally used as a medicinal plant. While its bioactive compounds have been studied, their concentrations in different parts of the plant have not been reported. This study compared total phenolic content (TPC), flavonoids, saponins and antioxidant properties, as well as major individual phytochemical compounds in the whole root, root bark, root wood, whole stem, stem bark, stem wood, and leaf of S. spinescens. The results showed the leaf had significantly highest 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 and root bark contained the highest concentrations of phytochemicals, these plant parts are recommended as starting material for future studies, to further isolate and identify the major compounds from S. spinescens and investigate their biological properties for use in pharmaceutical and food applications.
Scaevola spinescens is endemic to Australia and has traditionally been used by Aboriginal and Torres Strait Islander communities to treat a variety of conditions including colds, flu, fever, stomach pain, urinary disorders, sores, tinea, leprosy, and cancer. Extracts prepared from S. spinescens are non‐toxic and have been linked with various medicinal properties including antiviral, antibacterial, anti‐inflammatory, and anticancer activities. These studies support the ethnopharmacological use of S. spinescens by Indigenous peoples of Australia and highlight the need for further investigations on the plant for potential use in pharmaceutical and food applications. This review provides a comprehensive, up‐to‐date review of the literature on S. spinescens focusing on the traditional use, medicinal properties, phytochemicals, and factors that affect their composition during pre‐treatment and extraction, as well as providing a framework for future studies of the plant.
Background:
Scaevola spinescens is an endemic Australian shrub that is linked to various health benefits and traditionally used as medicine by decoction. To date, the extraction efficiency of the plant under various conditions has not been well understood. This study aimed to optimize aqueous extraction conditions of S. spinescens, for maximum extraction of total phenolic compounds, flavonoids and saponins, as well as antioxidant activities.
Methods:
Response surface methodology was used to determine the influence of four independent parameters including temperature, time, sample-to-water ratio and pH. The optimal ranges of temperature (60-90 °C), time (30-60 min), sample-to-water ratio (2-6 g/100 mL) and pH (3-7) were determined in preliminary experiments. Following assessment and optimization of the response surface methodology models, validation experiments were conducted to compare predicted and experimental values.
Results :
The RSM models showed that extraction temperature, time and sample-to-water ratio significantly affected total phenolic compound yields. Extraction temperature and time significantly affected flavonoid yields, while only sample-to-water ratio significantly affected saponin yields. Optimal conditions for extraction were determined to be: 90 ºC, 53 min, 2:100 (g/mL), and pH of 4.5, if saponins are the target compounds for extraction. For phenolics, flavonoids and antioxidant capacity, a higher sample-to-water ratio of 6:100 (g/mL) is recommended.
Conclusion:
Response surface methodology proved to be a reliable method for predicting yields of bioactive compounds and antioxidant capacity in S. spinescens. These findings can be used for efficient decoction by practitioners and end users, or by researchers for further isolation and purification of bioactive compounds from S. spinescens extracts.
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